Inhomogeneous distribution of proppant
FIELD: oil and gas industry.
SUBSTANCE: group of inventions is referred to intensification of hydrocarbons production from formation by hydraulic fracturing. The method of proppant induced aggregation in hydraulic fracture crack includes makeup of the proppant carrier fluid, which viscosity is increased by usage of polymer gel capable of syneresis; injection of the proppant suspension and the above fluid to the well; initiation of gel syneresis with formation of proppant aggregations. According to the second version the method includes initiation of polyelectrolyte complex formation with proppant aggregations. According to the third version the method includes makeup of the proppant carrier fluid containing polymer at temperature less than its critical solution temperature; injection of the proppant suspension and the above fluid to the underground formation at temperature more than the lowest limit of polymer critical solution temperature with formation of proppant aggregations.
EFFECT: inhomogeneous distribution of proppant in hydraulic fracture cracks, which increases conductivity and productivity of the well.
31 cl, 2 tbl, 12 ex, 5 dwg
Background of the invention
The present invention relates to enhanced recovery of hydrocarbons from the formation method of hydraulic fracturing. In particular, the invention relates to methods of heterogeneous placement of the propping agent (NRA) in the cracks, which increases their conductivity and well productivity. NRA is achieved by the formation of clusters of propping agent in the fracture in situ with the use of phase transitions or chemical reactions in polymer gel.
There is a need to provide a method of inducing heterogeneous placement of the propping agent in hydraulic fractures in underground formations, which does not require significant changes in the viscosity or concentration of the propping agent in the injected suspension.
Brief description of the invention
One of the embodiments of the present invention is a method of inducing the aggregation of propping agent in the hydraulic fracture, comprising the steps (1) preparation of liquid media propping agent, the viscosity of which is increased by the use of the first polymer gel, subjected to compression; (2) the injection of suspension of propping agent and the said fluid into the well; and (3) initiation of syneresis of the gel. Mentioned carrier fluid may contain fiber into�on, and the part used propping agent may have a polymer coating.
In one embodiment, the described implementation of the mentioned polymer gel is a crosslinked gel, such as borate crosslinked polymer gel, and the syneresis is initiated by the introduction of the gel polyvalent cation. Mentioned polyvalent cation is a cation of a metal selected from, for example, Ca, Zn, Al, Fe, Cu, Co, Cr, Ni, Ti, Zr, and mixtures thereof. The said cation is introduced into the gel, for example, by dissolving or slow dissolution, such as a salt, oxide or hydroxide of the cation. Additionally, at the time of initiation of syneresis mentioned cation may be present in the form of hydroxide or formed in situ hydroxide.
In another embodiment, the described implementation of the syneresis is caused by excessive cross-linking of the polymer gel. Excessive cross-linking of the gel may be delayed, for example, by inhibiting the cross-linking agent, or may be induced, for example, encapsulated crosslinking agent, slowly soluble cross-linking agent, or temperature-activated cross-linking agent.
In yet another embodiment, the described implementation, the syneresis is invoked by introducing into the composition of the liquid, in addition to the polymer of the first polymer gel, the second poly�EPA and agent arrested for the second crosslinking of the polymer. This second polymer is optionally present at a concentration below the concentration of the crossover.
In other embodiments, the described implementation, the syneresis is called superabsorbers polymer is initiated or the second fluid in contact with the propping agent of the carrier liquid directly into a hydraulic fracture.
Another embodiment of a method of inducing the aggregation of propping agent in the fracture fracturing includes the stages of (1) preparation of liquid media propping agent containing (i) at least one anionic polyelectrolyte or a precursor of at least one anionic polyelectrolyte, and (ii) at least one cationic polyelectrolyte or a precursor of at least one cationic polyelectrolyte; (2) the injection of suspension of propping agent and the said fluid into the well; and (3) initiation complex formation of polyelectrolytes. Mentioned carrier fluid may further contain fiber, and at least part used propping agent may have a polymer coating.
In various embodiments, this implementation the education of the polyelectrolytes is induced pH changes; referred to the formation of the complex polyelectrolytes is induced turned�eat at least one precursor polyelectrolyte in polyelectrolyte; referred to the education of the polyelectrolytes is induced by the formation of cationic polyelectrolyte directly in the hydraulic fracture; and mentioned cationic polyelectrolyte is formed directly in a hydraulic fracture in the Mannich reaction or as a result of decomposition of polyacrylamide according to Hoffmann; referred to the formation of the complex polyelectrolytes is induced by the formation of anionic polyelectrolyte directly in the hydraulic fracture; and mentioned anionic polyelectrolyte is formed directly in a hydraulic fracture during hydrolysis; at least one electrolyte or the precursor polyelectrolyte source is present in the fluid in the inner phase of the emulsion; at least one electrolyte or the precursor polyelectrolyte source is present in solid form; the formation of the complex polyelectrolytes is delayed in time by introducing at least one polyelectrolyte in the liquid in the form of complex polyelectrolyte-surfactant; and referred to the initiation of a second liquid which is brought into contact with the propping agent of the carrier liquid directly into a hydraulic fracture.
Another variant of the invention is a method of inducing the aggregation of propping agent in the fracture of hydrometry�and, including steps (1) preparation of liquid media propping agent containing the polymer at a temperature less its lower critical temperature of dissolution; and (2) the injection of suspension of propping agent and the said fluid into a subterranean formation at a temperature higher lower critical dissolution temperature of the polymer. Mentioned carrier fluid may further contain fiber, and at least part used propping agent may have a polymer coating.
Brief description of the drawings
Fig.1 shows the dependence of the degree of syneresis time for samples borate crosslinked guar gel with different concentrations of Ca(OH)2at room temperature.
Fig.2 shows degree of syneresis for borate crosslinked guar gel with different concentrations of Mg(OH)2at room temperature.
Fig.3 shows degree of syneresis for samples borate crosslinked guar gel with different concentrations of AlCl3·6H2O.
A detailed description of the invention
Although the following discussion, the focus is on hydraulic fracturing, are the subject of the present invention, phase transitions and chemical transformations in polymer gel can be used to conduct hydraulic fracturing, sprinkled well, as well as combined�I fracturing and sprinkled wells in a single operation. Description of the present invention is given for the example of the processing of vertical wells, but it is equally applicable to wells of any orientation. Description of the invention given with the example of wells for the production of hydrocarbons, but it is understood that the present invention can also be used in wells for production of other fluids, such as water or carbon dioxide, or, for example, injection wells and wells storage. It is also understood that under this description when referring to any range use, relevant, etc., concentrations or quantities refers to any concentration or quantity within this range, including the start and end points. In addition, each numerical value should first be read as having the definition of "approximately" (if no such definition in the text), and in the future to read as not having such a determination, unless the context otherwise agreed. For example, range from 1 to 10" refers to all without exception possible numbers in a continuous set between approximately 1 and approximately 10. In other words, in the case when given some range, even if only a few specific points specified explicitly or implied within this range, or even if none of� point is not implied within this range, it should be borne in mind that the authors of the invention take into account and understand that without exception, all points are treated as given, and that the authors of the invention have the whole range and all points within the specified range.
Although hydraulic fracturing is currently one of the most important and widely used methods of intensification of production from the reservoir, it is still not without serious fundamental limitations that reduce the production of hydrocarbons. When performing standard operations on stimulation of production in the well is pumped gelled fluid flow rate and pressure sufficient to fracture the formation; the resulting crack is filled with a propping material, usually delivered in a crack with the same liquid. Enter the propping material is intended to prevent the closure of cracks and, as a rule, is a sand or ceramic granules. Produced in this layer propping material provides hydraulic permeability by orders of magnitude greater than the initial permeability of the formation, thereby facilitating the flow of produced fluids in the wellbore. However, despite considerable efforts on the development of new riving materials with optimized properties (high resistance giving�the experiences, low density and low cost), the resulting conductivity (permeability) rasklinivaem traditional agents of cracks can still play the role of factor limiting production of the target fluid.
Non-uniform placement of the propping agent (NRA), such as the placement of the propping agent in the fracture in the form of compact clusters (e.g. supports) and thereby creating open channels in the fracture, can dramatically increase the conductivity of the fracture compared to the level achievable for standard ways of placing propping agent. In contrast to the approach in which the placement of the propping agent is mainly determined by the special regime of pumping fluid into the well, the present invention describes a class of ways of NRR in which clusters of propping agent, i.e. agglomerates or aggregates, generated in situ directly in the crack, and the time of formation of clusters and their placement are controlled by chemical means using the phase transitions or chemical reactions in polymer gel.
In one of the embodiments of the present invention in polymer gel is used as a thickener fluid for hydraulic fracturing, purposefully induced syneresis. Usually this process is considered quite undesirable, because the syneresis� dramatically change the rheological properties of fluids for hydraulic fracturing and often special measures to eliminate or weaken. However, with proper control, the syneresis with the release of water from the gel may lead to aggregation of the particles of propping agent. The resulting clots polymer capture the propping agent and keep it inside yourself; distances between particles in such clots are much shorter than in the original homogeneous suspension. Holding the crack from closing aggregates (clusters) of propping agent are separated by channels, which greatly increases the conductivity of the crack.
In another embodiment of the present invention mentioned clots polymer formed by chemically-initiated interaction between two different polymers. As an example, the formation of complexes between two oppositely charged polyelectrolytes. The formation of such complexes is accompanied by aggregation of the particles of propping agent and as a consequence NRRA. In yet another embodiment of the present invention, aggregation of propping agent in the clusters is the result of a phase transition in the polymer solution. In polymer solution with the lower critical dissolution temperature at the temperature of the reservoir occurs the separation of the phases, and the resulting �Sadok polymer bonded to each of the particles of propping agent.
Aggregates of particles of propping agent formed using methods that are the subject of the present invention can be further procnames by polymerization of applied polymer coating using fibers or any other means known to those skilled in this field.
The present invention discloses a method of forming a heterogeneous cluster of propping agent with the use of phase transitions in the gel and chemical transformations leading to aggregation of the particles of propping agent.
The formation of heterogeneous structures propping agent means constituting the subject of the present invention, can be controlled by syneresis of the gel fracturing. For the purposes of the present invention, the syneresis is defined as the process of separating water from the gel. The compression leads to phase separation of the gel and the formation of the aqueous phase caused by the destruction of the gel. If the gel contains particles of propping agent, the process of syneresis leads to their aggregation, which in General depends on the degree of shrinkage of the gel. In the present invention, the compression can be adjusted by various means.
One preferred method of initiating and controlling syneresis is to use borate crosslinked polymer gels and polyvalent katio�s. It is believed that the described method is also applicable for working with gels made with titanium and zirconium. For example, the addition of calcium hydroxide in borate crosslinked gel causes syneresis of the gel. For example, calcium chloride, borate and polymer are mixed on the surface. A mixture of the hydroxide or the source of the detainee education hydroxide, such as magnesium oxide, to generate calcium hydroxide in situ. The syneresis occurs after administration of a sufficient amount of the hydroxide of the polyvalent cation. Preferred is the generation of the above-mentioned hydroxide of the polyvalent cation in situ. The higher the amount of calcium ion, the deeper and faster the syneresis. Can be used and other polyvalent cations, such as Zn, Al, Mg, Fe, Cu, Cr, Co, Ti, Zr, and (or) Ni. The degree of syneresis depends not only on the concentration of polyvalent cation, but also on the density of the borate crosslinking. It should be noted that budget can be used and (or) unmodified guar, as the viscosity is not critical function and because the presence of impurities that enter the agglomerates of particles of propping agent, now is not a problem.
Another way to initiate and control of syneresis is to use excessive crosslinking of the gel. In the industry it is well known that high concentrations�AI crosslinking agent can lead to an increase in the density of crosslinking and ultimately to the destruction of the gel, what often taken special measures to prevent excessive crosslinking. However, in the present invention for initiating a controlled syneresis is used at least one crosslinking agent and (or) at least one delay mechanism of crosslinking. The use of more than one crosslinking agent and / or delay mechanism allows you to perform initial fix with standard suspension viscosity and the desired degree of crosslinking, thereby ensuring quality delivery of propping agent deep into the crack. Subsequent excessive cross-linking of the gel is directly in the crack and triggered either by a crosslinking system than the system that are active when the primary fix or an additional delay mechanism of crosslinking, or both of these factors. Agents delay the crosslinking known to those skilled in the art; examples include polyhydric alcohols, encapsulated crosslinking agents, slowly soluble crosslinking agents, and pH-controlled and (or) temperature-activated crosslinking agents. Slowly soluble crosslinking agents can be used in pure form or can be set on/applied to/embedded in the particles of propping agent. For the purposes of the present invention may be used various systems of crosslinking, such as systems based on boron, any of�honest in this area crosslinking system based metal such as zirconium, chromium, iron, boron, aluminum and titanium), and systems based on organic compounds (such as aldehydes, dialdehyde, phenolaldehyde composition, multifunctional amines and iminy). In all cases, a slow increase in the concentration of crosslinking agent in the gel leads to a controlled excess cross-linking of the gel and syneresis. The size of the resulting gel aggregates (clumps) is governed by shear history, gel composition and environmental conditions.
Another method of controlling the syneresis is to use selective crosslinking. In the mixture and sew massively polymers in which mentioned massively polymer performs the function of a thickener, and sew the polymer is present at a concentration below the concentration of crossover, sew the polymer with the cross-linking forms a so-called "microheli" (i.e. the gel fragments that can't be overlapped with each other to fill the space). Such microheli are formed within a viscous matrix massivemocha polymer. It is also possible to use mixtures of two polymers and two cross-linking agents, in which each crosslinking agent produces cross-linking only one of those present in the mixture of polymers. One pair of polymer/crosslinking agent provides thickening fluid, and the second pair of polymer/crosslinking agent forms microheli. �also mentioned thickening polymer may be crosslinked standard for purposes of hydraulic fracturing, as mentioned microheli can be formed later to ensure heterogeneity of placement of the propping agent. Examples of such systems include (1) a polymer matrix = guar/borate + polymer microgel = xanthan gum/Cr3+(the detainee) or (2) a polymer matrix = guar/borate + polymer microgel = polyacrylamide/Cr3+(the detainee) or polyacrylonitrile (the detainee, for example, with the use of hexamethylenetetramine).
Another method of controlling the compression is to use a mixture of polymers. The composition of such a mixture may include polymers of similar types (e.g. different polysaccharides, such as source of guar and carboxymethyloxime) or polymers of different types (for example, polysaccharides and polyacrylamides). As the crosslinking system may be used, for example, any of the above systems. Various affinity cross-linking agent different polymers leads to the formation regions of the gel with different viscosities. The size and distribution of such areas may be regulated by the composition of the solution, the mixing efficiency and the properties of the individual polymers.
Another method of controlling the compression is to use a Central antimicrobial highly absorbent polymers (SAP) for pulling water from cross-linked gel. Molecular weight and chemical properties of the used SAP can be p�reach so so that the osmotic pressure resulted in the transport of water from the gel phase to a phase of SAP. The loss of gel water in turn leads to aggregation of the particles of propping agent. Superabsorbent polymers may be administered in suspension in a dry or partially swollen. The degree of swelling and the selection is used in conjunction with SAP solvent can be used to control competing swelling of the gel and SAP. In addition, the water absorption of the superabsorbent may be triggered by changes in pH, ionic strength of the solution/gel, temperature, and other factors. Molecules SAP can be sewn and unsewn.
Another method of controlling the syneresis is the addition of fibers, for example fibers of polylactic acid in any of the above-mentioned systems. Fiber does not affect the degree of syneresis, but they determine the volume occupied useshim gel. The higher the number of fibers used, the more the final volume of the gel phase at the same degree of syneresis. Moreover, the presence of fibers significantly alters the mechanical properties of the gel phase.
Solutions of polyelectrolytes are widely used in various oilfield technologies, usually providing a unique combination of properties. Karboksimetilirovaniya Gary and cellulose (such as carboxymethylate (KMG), carboxymethyl�rocketpropelled (cmpg), carboxymethylcellulose (CMC), polyanionic cellulose, , etc.) represent the most widely used polymers of this type are used in drilling fluids and fracturing gels. These functionalized polysaccharides are polar carboxyl groups which increase the solubility of the polymer in water, increase its chemical resistance and allow the use of metals for joining. Many natural and semi-synthetic polymers also represent a polyanions, for example, xanthan gum, carrageenan, lignosulfonate, etc., Among purely synthetic polyanions special role is played by the polymers based on polyacrylic acid and polyacrylamide. They are used as flocculants, drying and lubricating agents, and have many other applications. Polyacrylamides contain anionic groups or in connection with the natural hydrolysis of acrylamide to acrylic acid, or due to the presence purposefully introduced sulfonic groups (as, for example, in acrylamido-2-methyl-1-propanesulfonic acid (AMPS)). Complexes of guar with borate-ion demonstrate polyanionic properties in a basic environment.
The polycations in oilfield technologies are not as widely as they are usually more expensive than the corresponding anionic counterparts. Prima�s the most frequently used polycations include various copolymers of polyacrylamide with chloride of diallyldimethylammonium (DADMAC), chloride of acryloyldimethyltaurate and other Quaternary ammonium monomers, polyvinylpyrrolidone, polyethyleneimine (PEI), and natural polymers such as chitosan, gelatin (and other polypeptides) and poly-L-lysine.
The interaction of oppositely charged polyelectrolytes in solution leads to aggregation and formation of polyelectrolyte complex (PEC). During the formation of the PEC is the release of a nearby charged groups of free polyelectrolytes small counterions, leading to the winning of entropy, which is the main driving force of this interaction. The long-chain polyanions and polycations, each with their own small organic or inorganic counterions that form complexes of polymers in which they play the role of counterions to each other, so that the original small counterions are not included in this complex. In the formation of complexes can contribute and other effects, such as education miaocheng hydrogen bonds, hydrophobic interactions, etc.
There are several types of structures peck. One of them is based on the formation of almost stoichiometric complexes between polyelectrolytes close molecular weight; such a structure is usually called the complex "ladder" type, it's the opposite of dawn�enny polymer chains are aligned relative to each other and ion interconnected (as shown on channel A, Fig.4). Also known water-soluble ordered non-stoichiometric complexes with ladder-type structure. In more disoriented peck, to describe the structure which uses the term complexes "mlechnogo" type, polymer chains are in the collapsed state and form a structure with a statistical charge compensation (as shown for the case B, Fig.4). Such complexes are often highly non-stoichiometric ratio of the components of polyelectrolytes and are usually characterized by very low solubility. The use of complexes of this type is one of the embodiments of the present invention.
The formation of the PEC with the structure "mlechnogo" type allows you to capture particles of propping agent in polymer clots. It should be noted that in this case the power of aggregation, retention of particles in the cluster is significantly higher than in the case of flocculation. Flocculation is widely used in water treatment; captured with flocculation of the particles typically have a size not exceeding about 150 microns (sieve No. 100, US standard). Organic flocculants, which usually consists of water-soluble polymers, forming molecular bridges between the particles, and the resulting flakes are held folded, but linear polymer chains. Clots peck, nab�of otiv, represent a three-dimensional network of polymer chains with a high degree of crosslinking, which may optionally, as in the case of flocculant, to have an affinity to the surface of trapped particles due to the formation of hydrogen bonds, electrostatic, van der Waals and other forces.
Education PEC can be regulated by various means. Known to specialists in this area of the inhibiting agents on the basis of the pH adjustment can be used to adjust the pH of the fluid for fracturing and initiate the formation of PEC in the crack. In non-limiting example, the slurry of hydraulic fracturing, in addition to propping agent and other additives, are two polyacrylamide copolymer, the first of which includes as one of the monomers acrylic acid, and the second includes as one of DADMAC monomer. When the pH of the slurry is maintained below approximately 4,0, most of carboxyl groups PAM-PA (polymer of acrylamide and acrylic acid is in the undissociated (protonated) form, and the polymer PAM-PA does not show the properties of the polyelectrolyte. With increasing pH of the slurry above about 5,0 begins dissociation of carboxyl groups and formed from PAM-PA polyelectrolyte complexation takes with PAM-DADMAC, forming low clumps peck with captured particles p�sklonovogo agent.
Another method for the controlled formation of PEC is the in situ synthesis of one of the polyelectrolytes directly in the crack. In non-limiting example, to obtain poly-particles from the source neutral PAM used the reaction of aminomethylpyridine on Manniche or decomposition polyacrylamide polymer according to Hoffmann. Both reactions occur in aqueous solution at temperatures above about 50°C. In the reaction of the Mannich PAM is treated with formaldehyde and an amine, which leads to the formation of major groups manniche (-NH-CH2-NR2), which are positively charged, even in solutions with relatively high pH values; the resulting product is a polycation. Preferably, the use of secondary amines, such as diethyl - and dipropylamine, but can be applied ammonia and primary amines. Formaldehyde can be generated directly in the crack of the predecessor (for example, hexamine (hexamethylenetetramine)), so that will not require the use of toxic substances. Another method of generating polyelectrolyte directly in the crack is the decomposition reaction of Hoffmann, in which PAM is processed hypogalactia in an alkaline solution with the formation of polyvinylene - cationic polyelectrolyte. A detailed description of chemical transformations PAM in terms� the reaction directly in the crack.
Another way of control (containment) education peck is the use of any type emulsion (oil-in-water, water-in-oil, water-in-water) for delivery to a crack of at least one polyelectrolyte. In non-limiting example, the slurry of hydraulic fracturing, in addition to propping agent and other additives are also stable under ambient conditions the droplets of the emulsion containing the polyelectrolyte, which, thereby, is directionspanel with respect to their oppositely charged partner, also present in the same suspension. The emulsion breaks or in the conditions of the reservoir (at elevated temperatures), or as a result of the use of agent detainee decomposition of the emulsion, and releases contained in the droplets polyelectrolyte, which immediately reacts education peck.
Another way to use the PEC consists in the introduction of one of the polymers or precursors of polymers in solid form.
Can be applied and any other ways controlled (delayed) education peck, for example, on the basis of temporary protection charged groups at least one of the polyelectrolytes by applying chemical protective group or a surfactant (when using complexes of polyelectrolyte-surfactant).
Other non-limiting examples of Yin�hiremore changes in the pH of the formation of the PEC include the following methods.
1. The use of a mixture containing polyethyleneimine (at alkaline pH in non-ionic form) and sulfonated polymer (retains an anionic charge at a high, neutral and low pH values of); Baek will not be formed as long as the pH of the medium changes from alkaline to acidic (polyethyleneimine go into a positively charged form). The desired pH may be initiated by a controlled hydrolysis of particles of polylactic acid and (or) polyglycol acid (PLA/PGA).
2. The use of a mixture of chitosan (which is insoluble at alkaline pH) and sulfonated polymer (retains an anionic charge at a high, neutral and low pH values of); Baek will not be formed until, until the pH of the medium changes from alkaline to the acid side (in this case, the chitosan is dissolved in the form of a cationic polymer). The desired pH can then be initiated by the controlled hydrolysis of particles of polylactic acid and (or) polyglycol acid (PLA/PGA).
3. The use of a mixture of poly-DADMAC (preserving cationic charge at a high, neutral and low pH values) and carboxylated polymer (which at high pH is in anionic form, but at a pH in the region of and below the pKa shifts in non-ionic form). In this case, the PEC are not formed in an acidic environment; to initiate the formation of PEC Tr�generally requires increasing the pH of the medium.
The initiators, different from the polymer complexes of the type Baek, will give a similar result. In addition to electrostatic interactions as the driving force for the formation of polymer complex can be used and other forces. As a non-limiting example, the systems based on hydrogen bonds give the effect, similar to the effect described above PEC. In a broader sense in the above description, instead of the PEC can be complex, which includes at least one polyelectrolyte. This can form polyelectrolyte complexes with various compounds, such as non-ionic polymers, surfactants and inorganic particles (e.g. metal ions).
Polymers with lower critical temperature (lcst)
Reacting to external stimuli polymers represent a wide class of modern functional materials. They are able to perceive small changes in external influences, such as pH, temperature, electrical/magnetic/mechanical field or luminous flux, and to make corresponding changes or transformation of the physical structure and chemical properties of the polymer solution or gel. Significant efforts have been focused on the development of the chemical structure and study of the properties responsive to a thermal effect, or thermocou�valid, of polymers. In particular, their structure, properties, and configuration demonstrate a highly sensitive response to temperature changes. Aqueous solutions of certain polymers are experiencing a rapid reversible changes in the vicinity of a lower critical solution temperature (lcst). Below NCTR chain of free polymer soluble in water and are fully hydrated expanded conformation. On the contrary, above NCTR polymer chains become more vibrophone that leads to the release of the polymer in a separate phase. The range of applications of thermosensitive polymers is very wide and includes the production of thermo - or pH-sensitive materials for drug delivery, biosensors, heat-sensitive coatings, catalysts, soluble polymeric ligands for purification from heavy metals, separation by particle size and dispersed in water hydrophobic thickeners for oil industry.
The solubility of most polymers increases with increasing temperature, but some NCTR-polymers have reverse temperature dependence of solubility. The largest group of temperature-sensitive polymers form polymers bearing amide groups. The most famous of them are poly-(N-isopropylacrylamide) and poly-(N,N'-diethylacrylamide). They have similar NCTR in the area 2-33°C. Poly-(ethylene oxide) (PEO) is one of the most studied biocompatible polymers, demonstrating NCTR-behavior. NCTR-transition of aqueous solutions of PEO occurs at temperatures ranging from about 100°C to 150°C depending on the molecular weight of the polymer. This temperature range extends the scope of PEO for heat-sensitive applications. The properties of the polymer solution, such as the phase transition temperature, determined by the chemical composition and molecular weight of the polymer and the characteristics of the environment such as pH, composition and concentration of ions.
Examples of polymers having a lower critical temperature of dissolution, without limitation include the following polymers: copolymers of ethylene and vinyl alcohol; copolymers of ethylene and of propylene oxide; copolymers of N,N-dimethylacrylamide and of methyl acrylate, ethyl acrylate, propylacetate, butyl acrylate, 2-ethoxyethylacetate and (or) 2-ethoxyethylacetate; hydroxypropyl cellulose; copolymers of N-isopropylacrylamide and acrylamide; copolymers of N-isopropylacrylamide and 1 deoxy-1 methacrylamido-D-glucitol; N-isopropylacrylamide; cellulose (with different concentrations of methyl substituents); copolymers of methyl cellulose and hydroxypropyl cellulose; polyphosphazene polymers, including poly[bis(2,3-dimethoxyphenoxy)fosfate],poly[bis(2-(2'-methoxyethoxy)ethoxy)fosfate], poly[bis(2,3-bis(2-methoxyethoxy)propanoic)fosfate], poly[bis(2,3-bis(2-(2'-methoxyethoxy)ethoxy)propanoic)fosfate] and poly[bis(2,3-bis(2-(2'-(2"-dimethoxyethoxy)ethoxy)ethoxy)propanoic)fosfate]; poly(ethylene glycol); block copolymers of poly(ethylene oxide)-b-poly[bis(methoxyethoxyethoxy)fosfate]; tribloc copolymers of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide); poly(N-isopropylacrylamide); block copolymers of poly(N-isopropylacrylamide) and poly[(N-acetylamino)ethylene]; poly(N-isopropylacrylamide); poly(propylene glycol); poly(vinyl alcohol); poly(N-vinylcaprolactam); poly(N-vinylsubstituted); poly(vinylethylene ether); poly(N-vinyl-N-propylacetamide); copolymers of N-vinylacetate and vinyl acetate; copolymers of N-vinylcaprolactam and N-vinylamine; copolymers of vinyl alcohol and vinylboronate; copolymers of N-vinylformamide and vinyl acetate, and combinations thereof.
Thermosensitive polymer flocculants can be used for aggregation of the particles of propping agent in the fracture. The diagram below shows a view of the mechanism of aggregation of the particles of propping agent using NCTR-polymer, see Fig.5. The mechanism of agglomeration of particles in this case involves the adsorption of the polymer on the surface of the particles at a temperature below NCTR. Under these conditions, the polymers are soluble in water, and between molecules floor�measure and hydrogen bonds of water are available; polymer chains are straightened conformation statistical coil. When the temperature rises above NCTR hydrogen bonds are weakened, which leads to phase separation of the polymer and water, wherein the polymer chain collapse and precipitate, capturing the particles of propping agent.
Describes the formation of precipitation NCTR-polymers also gives the opportunity to initiate the aggregation/agglomeration of the particles of propping agent. However, if the formation of precipitation NCTR-polymers remains similar water matrix liquid, its leakage is too large, and the crack will only polymer clots and the propping agent. On the other hand, it is possible to obtain a practically useful system if precipitation NCTR-polymers are formed in such a way that the remaining matrix is a viscous liquid with a small leak.
There are two ways of practical implementation of the present invention: injection into the crack of the same composition containing an initiating or inhibiting agent, or injected into the crack of two or more compositions that are mixed and react directly in the crack.
A typical sequence of stages induced when complexes of polyelectrolytes (PEC) agglomeration as follows: injection of fracturing fluid; injection containing propping �Gent suspension, which includes at least one polyelectrolyte is already charged in the form and at least one non-ionic polymer that can be turned into a polyelectrolyte charge opposite in sign to the charge of the first polymer, with or delaying initiating agent; aggregation propping agent; closing of the crack. The concentration of polyelectrolytes and predecessors polyelectrolyte is in the range from about 0.005 to about 5% by weight. Relevant to the purposes of the present invention, the mechanisms of initiation of education peck listed above. The slurry can also include other items used in the oil industry and known to those skilled additives such as thickeners, surfactants, stabilizers unstable clays, antibacterial agents, etc.
The sequence of stages for embodiments using agglomeration on the basis of syneresis of the gel is as follows: injection of fracturing fluid to create a fracture; injection containing the propping agent of the liquid with syneresis in terms of the formation; agglomeration propping agent; closing of cracks in the formed agglomerates. In a preferred embodiment of the implementation in the liquid composition also optionally includes fiber to stabilize agglomerates and protection from CE�ementati.
When using the approaches of agglomeration on the basis of NCTR-polymers, consider the following sequence of processing steps: injection of fracturing fluid to create a fracture; injection containing the propping agent liquid, undergo phase transition in reservoir conditions (for example, when heated to the temperature of the reservoir); agglomeration propping agent; closing of cracks in the formed agglomerates.
In the approach with the use and mixing of two different liquids agglomeration is induced by the injection of fracturing fluid to create a fracture, followed by injection of two liquid components in the region of the perforation in different ways, for example, by pumping a liquid through a flexible tube and another fluid through the annular space between the pipe and the borehole wall. Mixing of the two fluids in the perforating holes or behind them induces agglomeration propping agent. Agglomerated particles are transferred into the crack. After treatment, the fracture closes on the agglomerates.
The method constituting the object of the present invention can be applied to cracks of any size and orientation. A particularly promising application for conducting hydraulic fracturing in horizontal wells and (or) soft formations. Agglomeration and, as a consequence, non-uniform placement of the propping agent must� take place either at the stage of injection, or for an additional stage of technical settling well after treatment; they must occur prior to the influx into the wellbore.
The present invention can be better understood after considering the following examples.
Prepared a suspension of a linear gel in deionized water containing 3.6 g/l (30 lb/1000 Gal) Guara and 406 g/l (4 ppa) sand particle size 0,300-0,106 mm (sieve No. 50/140, US standard). Then the gel is made using different concentrations of cross-linker (see table 1). As a cross-linking agent used a mixture of H3BO3:NaOH:CaCl2with the weight ratio of 3.1:1:1,3, in which the solids content was 50% by weight. in the water. In the sample with the highest concentration of borate in three hours observed a marked destruction of the gel, whereas in the gel sample with the lowest concentration of crosslinking agent no changes found. After 24 hours exposure at room temperature measured volumes of water released from the samples of the gel. Found that after syneresis all the particles of propping agent remained in the gel phase, where the concentration of the propping agent is increased to 2 times.
|Sample No.||EXT�been crosslinking agent, ml||The volume of the aqueous phase after 24 hours, %||The concentration of the propping agent after syneresis, g/l|
Using deionized water, prepared sample 1 reagent water-based, emulsion-type water-in-oil" anionic copolymer of polyacrylamide and AMPS used to reduce friction, in a concentration of 0.1% weight. (1 ppm); in the sample added approximately 10 mg of the dye is methylene blue. Using deionized water, prepared sample 2 reagent water-the basis of emulsions of the type water-in-oil" cationic polyacrylamide, also used to reduce friction, in the same concentration; the sample was added to approximately 10 mg of methyl orange.
In one experiment, 20 ml of sample 1 was placed in a Petri dish, and have added 20 ml sample 2 a Petri dish was shaken manually for mixing the two samples. After about 1 minute of this mixing appeared and began to grow a grid of thin green lines representing a range of polyelectrolytes, painted with a mixture of dyes. The mesh was sticky, and its further growth with stirring led to the formation of polymer clot. In the second experiment, 4.8 g of sand with a particle size of 400-800 microns (sieve No. 20/40, US standard) dispersively in 20 ml of the sample 1, having a concentration of propping agent about 240 g/l (2 ppa). Then to the resulting suspension of propping agent is slowly added 20 ml of sample 2, and mixed it into the mixture. Grain of sand fractions 20/40, source uniformly dispersed in the mixture, while gathered in aggregates of green.
Studied the syneresis of gels made in deionized water, 3.6 g/l of guar, 0.5 g/l of boric acid and 3 ml/l 5% (%wt.) NaOH solution with addition of different amounts of Ca(OH)2. Used Ca(OH)2had a grain size of 0.6-0.3 mm (sieve No. 30/50). The syneresis, in the course of which at room temperature it took almost a day, at a temperature of 50°C was held for several hours. The degree and speed of compression is governed by the input concentration of cations. Fig.1 shows the dependence of the degree of syneresis time for samples borate crosslinked guar gel with different �koncentracije Ca(OH) 2at room temperature. The syneresis in these systems began when the concentration of Ca(OH)2approximately of 0.014 mol/l.
Studied the kinetics of syneresis in the presence of magnesium ions. The gels were prepared in deionized water containing 3.6 g/l of guar, 3.6 g/l H3BO3and 23 ml/l 5% (%wt.) NaOH solution with the addition 0,142-1.3 g/l MgCl2and the appropriate amount of NaOH for the formation of Mg(OH)2. Fig.2 shows degree of syneresis for borate crosslinked guar gel samples with different concentrations of Mg(OH)2at room temperature. The syneresis in these systems began when the concentration of Mg(OH)2approximately 0.005 mol/l.
Studied the kinetics of syneresis in the presence of aluminum ions. The gels were prepared in deionized water containing 3.6 g/l of guar, 3.6 g/l H3BO3and 23 ml/l 5% (%wt.) NaOH solution with the addition 0,178-3,26 g/l AlCl3·6H2O and the appropriate amount of NaOH for the formation of Al(OH)3. Fig.3 shows degree of syneresis for samples borate crosslinked guar gel with different concentrations of AlCl3·6H2O. it is believed that was the formation of Al(OH)4-; syneresis started at a concentration of about 0,004 mol/l.
In deionized water was prepared gels of 0.014 mol/l of aluminum (3.6 g/l of guar, 3.6 g/� H 3BO3, about 3.26 g/l AlCl3·6H2Oh, and 55.4 ml/l 5% (%wt.) NaOH solution) and added to the samples with different amounts of fibers of polylactic acid size 6-8 mm Concentration of the fibers were in the range from 0 to 10.3 g/l. After the amount of syneresis usesage gel was dependent on the concentration of fiber; the greater the number of fiber was added, the greater was the amount of the gel up to about 3.6 g/l of the fiber. The change in the concentration of fibers from 3.6 to 10.3 g/l practically does not lead to visible changes in the syneresis of the gel.
Studied the effect of density borate crosslinking degree of syneresis. Prepared two samples crosslinked gel with added copper ions, characterized by the concentration of borate. The first sample was prepared in deionized water containing 3.6 g/l of guar, 0,652 g/l CuCl2·2H2O, 3.6 g/l H3BO3and 29.1 ml/l 5% (%wt.) NaOH solution. The second sample was prepared in deionized water containing 3.6 g/l of guar, 0,652 g/l CuCl2·2H2O, 0.5 g/l H3BO3and 9.1 ml/l 5% (%wt.) NaOH solution. After two hours exposure at room temperature, the degree of syneresis was equal to 70% in the sample with a high concentration of boric acid and 9% in the sample with low concentration of boric acid.
Three grams of sand grain size 0,212-0,106 mm (sieve � 70/140) (d 50anyway 169 μm according to the analyzer Malvern Mastersizer) was placed in a Petri dish containing 20 ml of deionized water and 0.8 g of poly(N-isopropylacrylamide) (average Mnabout 20000-25000); the polymer has NCTR 32°C. the resulting suspension for one minute intensively stirred at room temperature on a magnetic stirrer. Agglomeration was not observed. Then the suspension with stirring heated to a temperature of 40°C. When the temperature reached 40°C, stirring was stopped and observed the formation of agglomerates. The average size of the formed agglomerates estimated from measurements on the photographs of the sample vessel on the background of a graduated ruler. The average size of the agglomerates obtained under dynamic conditions (with vigorous stirring) was approximately 0.9 cm. Analysis of agglomerates showed that they consist of sand and the precipitated polymer.
Demonstrated the use of complexes of polyelectrolytes to agglomerate the particles of propping agent. Studied the agglomeration of sand grain size 0,850-0,425 mm (sieve No. 20/40) in the complex polyelectrolytes (PEC) formed from partially hydrolyzed polyacrylamide (PHPA) (statistical anionic copolymer consisting of 40 mol%. sodium acrylate and 60 mol%. acrylamide and having an average molecular weight of approximately 10×106 g/mol) and polyethyleneimine (PEI) (sellersville cationic polymer with an average molecular weight of approximately 8×105g/mol). The typical structure PEI has the following form:
In a glass of 250 ml of the prepared suspension of 10 g of sand with grain size 0,850-0,425 mm (sieve No. 20/40) in 100 g of deionized water, using for mixing a two-blade agitator with mechanical operation upper and rotation speed of 270 rpm With continuous stirring (270 rpm) added 25 grams of a one percent (by weight) solution of PHPA in a two percent (by weight) solution of KCl. After 10 minutes of continuous stirring was added 2.5 g of 10-percentage (by weight) solution of PEI in deionized water and continued stirring for another 15 minutes. In this phase, the aqueous phase solution contained 0,196% by weight. PHPA polymer, 0,196% by weight. polymer PEI and 0.39 wt%. KCl. the pH of the aqueous phase was sufficient alkali to maintain the polymer PEI in uncharged form, which inhibited the loss of a peck. Then to induce protonation of PEI polymer and deposition peck added acid, again with continuous stirring (270 rpm) to the mixture were added 2 g of 1-molar HCl, using a Pasteur pipette for the introduction of the acid solution into a stirred saturated mixture. After a few minutes of continuous mixing was formed very friable sticky residue peck.After a few minutes the precipitate-pack shrank to a small fraction of the full volume of the mixture and completely encapsulated within itself (agglomerated) 10 g of sand; traces of sand on the bottom of the glass left. The described experiment showed 100% efficacy Metropolitan area (EA), where EA is defined as the percentage by weight of sand, encapsulated/agglomerated peck. After adding the acid and subsequent thorough mixing, the pH of the aqueous phase was 9.5. At such pH PEI was in quite a protonated (cationic) form for the strong interaction, by electrostatic attraction, with anionic carboxylate sites PHPA polymer. This led to the observed formation of sticky sludge PEC. The same 100% efficiency of agglomeration for the same sand got in similar experiments with a final pH of 8.5 and 10.0.
As a further demonstration of the agglomeration of sand grain size 0,850-0,425 mm (sieve No. 20/40) conducted additional experiments in polyelectrolyte complexes (PEC) formed from the same polymer PEI and PHPA that in example 9. The experiments were carried out as described in example 9, but this time varied ratios of PEI and PHPA, and instead of deionized water used 100 g of two percent (by weight) aqueous solution of KCl. As expected, the higher the ionic strength a two percent aqueous solution of KCl resulted in some strong screening of the electrostatic interaction between oppositely charged polymers. Paul�obtained results are shown in table 2. Again received high EA even in the presence of salt, but this time it has not reached 100%.
|The composition of the aqueous phase (before the introduction of the acid)||Fluid Foundation||the pH after addition of acid and mixing||EA|
|0.2% weight. PHPA, 0.1% weight. PEI||2% by weight. KCl||9,1||66|
|0.2% weight. PHPA, 0.2% of the weight. PEI||2% by weight. KCl||9,2||71|
|0.2% weight. PHPA, 0.3% of the weight. PEI||2% by weight. KCl||9,3||80|
You can see that when the concentration of PEI, there is some increase in EA.
Studied the agglomeration of sand grain size 0,850-0,425 mm (sieve No. 20/40) in the polyelectrolyte complex (PEC) formed by kompleksowego guar borate (which is an anionic polymer and a cationic copolymer of acrylamide and DADMAC. In a glass of 250 ml of the prepared suspension of sand grain size 0,850-0,425 mm (sieve No. 20/40) in 100 g of a linear gel containing 1.2 g/l guar�, 0.46 g/l of boric acid and 0.1 g/l of a copolymer of acrylamide and DADMAC, using for mixing agitator with mechanical operation upper and rotation speed of 500 Rev/min the Aqueous phase was approximately neutral pH. After 5 minutes of continuous mixing added 6 ml/l of a 5% (by weight) NaOH solution, which led to the formation of the guar-borate complex and the precipitation peck. Almost all the sand has been in the precipitated phase.
Checked the influence of the ionic strength of the solution on the degree of syneresis. Prepared two samples crosslinked gel with different concentrations of potassium chloride. The first sample was prepared in deionized water, 3.6 g/l of guar, 7 g/l H3BO3and 42 ml/l of 5 wt%. NaOH solution. The second sample was prepared in deionized water, 3.6 g/l of guar, 7 g/l H3BO3, 42 ml/l 5% (by weight) NaOH solution and 20 g/l KCl. After two hours exposure at room temperature, the degree of syneresis was 94% for the sample with potassium chloride and 0% for the sample without salt.
1. Method of inducing the aggregation of propping agent in the fracture of hydraulic fracturing, including stages: (1) preparation of liquid media propping agent, the viscosity of which is increased through the use of polymer gel capable of syneresis; (2) the injection of suspension of propping agent and mentioned�second fluid into the well; and (3) initiation of syneresis of the gel with the formation of aggregates of propping agent.
2. A method according to claim 1, wherein the mentioned carrier fluid also contains fiber.
3. A method according to claim 1, where at least part used propping agent has a polymer coating.
4. A method according to claim 1 where the above-mentioned polymer gel is a crosslinked gel.
5. A method according to claim 1 where the above-mentioned polymer gel is a borate crosslinked polymer gel, and the syneresis is initiated by the introduction of the gel polyvalent cation.
6. A method according to claim 5 where the above-mentioned polyvalent cation is a metal cation selected from the group consisting of CA, Zn, Al, Mg, Fe, Cu, Co, Cr, Ni, Ti, Zr, and mixtures thereof.
7. A method according to claim 5 where the above-mentioned polyvalent cation is introduced in a polymer gel by dissolving a salt, oxide or hydroxide of the cation.
8. A method according to claim 5 where the above-mentioned polyvalent cation at the time of initiation of syneresis is in the hydroxide form.
9. A method according to claim 1, where the said syneresis is triggered by excessive cross-linking of the polymer gel.
10. A method according to claim 9, where excessive cross-linking of the polymer gel detained by the use of the inhibiting cross-linking agent.
11. A method according to claim 9, where excessive cross-linking of the polymer gel is induced cross-linking agent encapsulated, slow�but soluble cross-linking agent or temperature-activated cross-linking agent.
12. A method according to claim 1, where the said syneresis is initiated by introducing into the composition mentioned fluid in addition to the polymer gel of the second polymer and agent arrested for the second crosslinking of the polymer.
13. A method according to claim 12, wherein the second mentioned polymer is present at a concentration below the concentration of the crossover.
14. A method according to claim 1, where the said syneresis is initiated superabsorbing polymer.
15. A method according to claim 1, which referred to the initiation of syneresis of the gel is made of the second liquid which is brought into contact with the carrier liquid propping agent directly in the hydraulic fracture.
16. Method of inducing the aggregation of propping agent in the fracture of hydraulic fracturing, including stages: (1) preparation of liquid media propping agent comprising (i) at least one anionic polyelectrolyte or a precursor of at least one anionic polyelectrolyte; and (ii) at least one cationic polyelectrolyte, or a precursor, at least one cationic polyelectrolyte; (2) the injection of suspension of propping agent and the said fluid into the well; and (3) initiation complex formation of polyelectrolytes with the formation of aggregates of propping agent.
17. A method according to claim 16 where the above-mentioned carrier fluid also ODS�RIT fiber.
18. A method according to claim 16, where at least part used propping agent has a polymer coating.
19. A method according to claim 16, which referred to the formation of the complex polyelectrolytes is induced by the change of the pH value.
20. A method according to claim 16, which referred to the formation of the complex polyelectrolytes is induced by a transformation of at least one precursor polyelectrolyte in the polyelectrolyte.
21. A method according to claim 16, which referred to the formation of the complex polyelectrolytes is induced by the formation of cationic polyelectrolyte directly in the hydraulic fracture.
22. A method according to claim 21 where the above-mentioned cationic polyelectrolyte is formed directly in the hydraulic fracture method selected from the Mannich reaction or decomposition of polyacrylamide according to Hoffmann.
23. A method according to claim 16, which referred to the formation of the complex polyelectrolytes is induced by the formation of anionic polyelectrolyte directly in the hydraulic fracture.
24. A method according to claim 23 where the above-mentioned anionic polyelectrolyte is formed directly in a hydraulic fracture during hydrolysis.
25. A method according to claim 16, where at least one polyelectrolyte or the precursor polyelectrolyte source is present in said liquid carrier in the internal phase of the emulsion.
26. A method according to claim 16, where at least one polyelectro�it or precursor polyelectrolyte source is present in solid form.
27. A method according to claim 16, where the formation of the complex polyelectrolytes is delayed in time by introducing at least one polyelectrolyte in said carrier fluid in the form of complex polyelectrolyte-surfactant.
28. A method according to claim 16, where the said initiating is performed by the second liquid, which is brought into contact with the carrier liquid propping agent directly in the hydraulic fracture.
29. Method of inducing the aggregation of propping agent in the fracture of hydraulic fracturing, including stages: (1) preparation of liquid media propping agent containing the polymer at a temperature less its lower critical temperature of dissolution; and (2) the injection of suspension of propping agent and the said fluid into a subterranean formation at a temperature higher lower critical dissolution temperature of the polymer with the formation of aggregates of propping agent.
30. A method according to claim 29 where the above-mentioned carrier fluid also contains fiber.
31. A method according to claim 29, where at least part used propping agent has a polymer coating.
FIELD: oil and gas industry.
SUBSTANCE: treatment method of underground hydrocarbon-containing formations involves the following: a) provision of a composition including a thickening initiator measuring pH, and a polymer capable of hydration in a certain pH range; b) pumping of a composition with pH value beyond the limits of the above pH range; c) activation of an action of pH thickening initiator for displacement of pH composition to the above range of its values, and d) provision of a possibility of increasing viscosity of the composition and shaping of a plug. According to another version, a processing method of underground hydrocarbon-containing formations involves the following: a) provision of a composition containing a polymer capable of hydration in a certain pH range; b) pumping of the composition with pH value beyond the limits of the above pH range; c) provision of a pH changing thickening initiator; d) activation of the action of the thickening initiator for displacement of pH composition to the above range of its values, and e) provision of a possibility of increasing viscosity of a composition and shaping of a plug. The invention has been developed in dependent claims.
EFFECT: improving efficiency of initiation and control of plug formation.
15 cl, 5 ex, 3 dwg
FIELD: oil and gas industry.
SUBSTANCE: in a carbonaceous oil deposit development method that includes drilling of horizontal wells with a core sampling from the productive formation, performance of core laboratory tests, acid treatment and multiple hydraulic fracturing of the formation in these wells, according to the invention the core is sampled at different sections along the whole length of the horizontal shaft. The sampled core is subjected to the laboratory tests to determine the fracturing pressure, at that the sections are identified along the shaft where the minimum fracturing pressure Pmin, MPa, and the maximum fracturing pressure Pmax, MPa is required. Each section is treated by acid; at that the acid concentration for each section is set as identical. During the acid treatment each treated section of the formation is isolated temporarily by packers from the remaining part of the well. Then multiple proppant hydraulic fracturing of the formation is made under pressure that does not exceed Pmax. At that at the sections, where Pmax is required the acid treatment is performed in a volume of Qmax, m3/m, at the sections where Pmin is required the acid treatment is performed in a volume not exceeding 10% of the maximum value. At the remaining sections the volume of the injected acid is defined proportionally to the obtained fracturing pressure in compliance with the following ratio:
EFFECT: improved sweep efficiency and increased oil recovery of the oil deposit.
FIELD: oil and gas industry.
SUBSTANCE: method includes running of production string with packer in to the well, setting of the packer, hydraulic fracturing by injecting fracturing fluid through production string with packer to the producing reservoir with further proppant injecting through perforated interval in the low-permeable bed, pressure releasing from the well. Additionally perforated interval in the low-permeable bed is isolated temporary, the interval of clay layer is perforated using alternating charges of large diameter and deep invasion; then the production string with packer is lowered so that the lower end of the production string is at the level of clay layer roof, the packer is set in the well, the low-permeable bed is fractured with formation of cracks by injection of fracturing fluid along the production string through perforated intervals in clay layer. Then bank of oil-based cross-linked gel is injected to cracks in volume of 3-5 m3 with flow rate of 10 m3/min. Proppant moisture is used as proppant. Then cracks are reinforced by dosed injection of fracturing fluid and proppant mixture starting with concentration of 400 kg/m3 for proppant mixture with stepped increase of its concentration in fracturing fluid per 200 kg/m3 for each dose and flow rate of 5 m3/min. The proppant mixture is made at the wellhead with the following ratio of components, wt %: proppant 12/40 mesh - 30%; proppant 18/20 mesh - 30%; quartz flour - 40%. Upon completion of hydraulic fracturing of low-permeable bed temporary isolation is removed from the perforated interval of the low-permeable bed with formation of hydraulic connection between the borehole and created fracture.
EFFECT: improved reliability of hydraulic fracturing for low-permeable bed with clay layers and bottom water.
FIELD: oil and gas industry.
SUBSTANCE: in the method of well operation stimulation including test injection of breakdown fluid and package of breakdown fluid with proppant, correction of the breakdown project and performance of fracturing in low-permeable reservoirs having absolute permeability less than 1mD, hydraulic fracturing is made with injection of flush fluid on the basis of 1.0-3.0 m3 per 1 t of proppant using proppant fractions, which include only fine fraction with size less than 30/60 mesh with final concentration of proppant less than 300 kg/m3; at injection of the fluid flow rate of 3.5 m3/min and more and concentration of gel formation is set less than 2 kg/m3, with final underflush of the mixture in volume of 0.1-0.5 m3.
EFFECT: simulation of the well opening the low-permeable formation.
SUBSTANCE: method involves drilling of a horizontal well, lowering to a vertical part of the well of a casing string and its cementing, lowering of a pipe string with a packer to a well, seating of the packer, formation of fractures of formation hydraulic fracturing (FHF) in the horizontal well shaft by pumping via the pipe string of fracturing fluid, and fixation of fractures by pumping of carrier fluid with proppant. The horizontal shaft is drilled perpendicular to direction of minimum main stress. FHF is performed by pumping of fracturing fluid with flow rate of 2-3 m3/min with formation of a longitudinal fracture in the formation relative to the open horizontal part of the well; crosslinked gel is used as fracturing fluid; then, fixation of a longitudinal fracture is performed by pumping via the pipe string of proppant of large fraction with carrier fluid - crosslinked gel. Then, FHF is performed by pumping of fracturing fluid with flow rate of 7-9 m3/min; line gel is used as fracturing fluid; after that, fixation of branched FHF fractures is performed by pumping of proppant of small fraction with carrier fluid - line gel.
EFFECT: improving FHF efficiency and reliability.
FIELD: oil and gas industry.
SUBSTANCE: method comprises test forcing of fracturing fluid and pile of fracturing fluid with proppant, correcting the fracturing project and performing of the main fracturing process. In highly permeable reservoirs with absolute permeability not less than 100 mD the main fracturing process is carried out with usage of proppant fractions, which include initial fraction with mesh size from 30/40 up to 20/40 and the main coarse fraction with mesh size of 12/18 and more in the volume not less than 70% of the total proppant quantity with final proppant concentration not less than 750 kg/m3. While injecting fraction with mesh size of 12/18 and more through perforated openings fluid consumption is set so that it does not exceed 3 m3/min and wellhead pressure is maintained at the level less than 35 MPa.
EFFECT: improving the efficiency of hydraulic fracturing for highly permeable strata.
SUBSTANCE: invention relates to a propping agent and use thereof in hydraulic fracturing for oil and gas extraction. The ultralight propping agent is prepared from a mixture of raw materials comprising porcelain clay, pottery clay and kaolin and/or siliceous clay, in the following content, wt %: porcelain clay 5-85, kaolin and/or siliceous clay5-85, pottery clay 5-30. The ultralight propping agent with apparent specific gravity of 2.10 g/cm3 to 2.55 g/cm3 and volume density of 1.30 g/cm3 to 1.50 g/cm3 is prepared from a mixture of natural clays comprising porcelain clay, pottery clay and at least kaolin or siliceous clay, where alumina content is 5.5-35%. In the method of preparing said filler, high strength of the propping agent is achieved by controlling firing time in the range of 75-90 minutes and firing temperature of 1150°C to 1380°C. Sintered spherical granules prepared from a mixture of raw materials comprising porcelain clay, pottery clay and at least kaolin or siliceous clay, having a substantially circular or spherical shape, are characterised by a Krumbein coefficient of at least 0.8 with alumina content of 5.5-35%. The hydraulic fracturing method includes pumping into an underground formation a hydraulic fluid with flow rate and pressure sufficient for opening a fracture in the formation, and the fluid containing said filler is pumped into the fracture.
EFFECT: high strength of the propping agent and conductivity thereof.
29 cl, 13 tbl, 5 ex
SUBSTANCE: method involves drilling of a horizontal well shaft, lowering and fixation of a shank with filters, lowering of a packer and its seating, formation of cracks in each of the zones, which correspond to intervals of parts of the horizontal shaft with insulation of the rest of its parts. With that, the lower end of a pipe string is located 1 m closer to the mouth from the distant formation interval; a string of flexible pipes is lowered into the above pipe string and it is equipped from below with an abrasive jet perforator; space between the pipe string and the string of flexible pipes is sealed at the well mouth. Groups of slit perforation holes are made with length of 20-30 cm and width of 15 mm with a phasing angle of 60° in every 1.5 m of the oil-saturated formation interval in the shank; reverse flushing is performed together with simultaneous movement of the string of flexible pipes from the mouth to the face throughout the length of the oil-saturated formation interval; the string of flexible pipes with a jet nozzle is removed, and hydraulic formation fracturing is performed with further fixation of a fracture by light-weight resin-coated propping agent with fraction size of 20/40 mesh in concentration of 1400 kg/m3 and its filling to the horizontal well shaft opposite the oil-saturated formation interval; the packer is removed; the pipe string is moved in the direction from the face to the mouth to the next oil-saturated formation interval; after that, the above operations are repeated starting from seating of the packer and ending with the packer removal in the rest oil-saturated formation intervals developed by the horizontal well shaft.
EFFECT: improving reliability of hydraulic formation fracturing and efficiency of fracture fixing.
SUBSTANCE: method comprises the formation exposing by vertical well, tripping in the well on the pipe string of the water jet tool with even amount of injection nozzles and its placement in the preset interval of the formation, injection of driving fluid through injection nozzles of the water jet tool for caving in the formation, subsequent formation fracturing from caverns by the spray stagnation pressure in caverns. Meanwhile the water jet tool with a series of injection nozzles, located along the tool with the interval between nozzles in a line no more than two diameters of the casing is used. The water jet tool is rotated to the preset angle to change the direction of progressing of each subsequent fracture. The fractures are formed at driving fluid injection pressure in the casing below the side rock pressure. Before tripping of pipe string into the well in the bottom end of the water jet tool the rotating device and mechanical packer are installed. To compensate leakages and the wedging of fractures during the process of hydraulic formation fracturing an acid is added in volume equal to 20% of the volume of the driving fluid, the driving fluid is injected into the pipe string through the water jet tool into a cavern until fracturing, then into the annular space of the well an acid is injected to compensate the leakages and fracture wedging. The pressure of acid injection into annular space of the well amounts 85% from the pressure created in the pipe string during progressing of fracture, upon termination of progressing fracture and the wedging of fracture in the same direction raise a pipe string on 1 m, turn a pipe string on an angle applicable to a direction of forming of following fracture, and lowered, then the process operations are repeated.
EFFECT: improvement of accuracy of orientation of fractures, performance and reliability of fracturing of carbonate reservoirs.
SUBSTANCE: method comprises the drilling of a horizontal well bore in oil saturated part of the productive formation of the well, tripping of the pipe string into the well, the forming of perforations and fractures using the a hydrofracturing of formation in the hole of horizontal well, successively, starting from the end of far from the vertical borehole axis. During the next hydrofracturing the section, through which hydrofracturing is performed, is insulated from another part of the string with a packer. During drilling of the horizontal well bore the permeability and porosity of rocks are determined and the intervals of the productive formation with low permeability and porosity of rocks are identified, and on completing of drilling the rock hydrofracturing pressure is determined in each interval of the horizontal borehole. Then the volumes of fracturing fluid and acid for each interval of the oil saturated part of the formation with low permeability and porosity are determined, then the pipe string is moved to the interval of the productive formation nearest to the borehole bottom, with low permeability and porosity, the mechanical packer is seated, from hole mouth using the pumping unit the gelled fracturing fluid is injected into the pipe string through nozzles of the water jet tool and reshape perforations, then, not stopping injection gelled of fracturing fluid on a pipe string, construct fracture pressure applicable to the given interval of the oil saturated part of the productive formation. After 30% drop of pressure of injection of gelled fracturing fluid in the pipe string the hydrofracturing fractures are formed, for this purpose into the annular space of the well an acid is injected at the variable flow rate ensuring maintaining of pressure of injection of gelled fracturing fluid in the pipe string 10% less than the fracture pressure for the given interval of the oil saturated part of the productive formation. The packer releasing is performed and the pipe string is removed from bottomhole to the mouth into the following interval of the oil saturated part of the formation with low permeability and porosity of rocks for forming perforations and conducting of a hydrofracturing of the formation with forming and progressing of fractures.
EFFECT: shortening time for formation hydrofracturing, improvement of performance and reliability of formation hydrofracturing.
SUBSTANCE: invention relates to manufacture of molded ceramic materials for use as propping agent in production of liquid and gaseous fluids from bored wells. Method comprises briquetting and heat treatment of aluminosilicates kaolin at 1150-1250оС. Resulting mix is ground to average grain size 3-5 μm and loaded into granulator. Before granulation, 1.2-3.0% mineralizer and 5-10% plasticizer are added. Mix is moistened with dozed amount of organic binder and stirred to form granules. At the end of granulation, fired ground material for powdering granules is added in amount 1.2-3.0%. Granules are dried and screened to isolate desired fraction, which is subjected to final firing at 1370-1450оС for 30-60 min and then re-screened into commercial fractions.
EFFECT: enabled manufacture of granules having low loose density and high strength allowing their use at depths up to 14000 feet (4200 m).
3 cl, 1 dwg, 1 tbl, 3 ex
FIELD: oil and gas production.
SUBSTANCE: proppant used in oil production involving hydraulic fracturing of formation contains ceramic granules coated with novolac resins supplemented by catalytic aqueous urotropin solution in organosilicon emulsion. Proppant preparation method comprises preparing granules and coating them. The latter operation is carried out as follows. Granules are heated to 150-160°C, dry novolac resin and catalytic urotropin solution are added at stirring in two equal portions with respect to the weight of resin and urotropin. When dropping temperature achieves 95-100°C, organosilicon emulsion is added provide following proportions of ingredients: 5.0-8.0% of novolac resin, 1.5-3.0% of 33% urotropin solution, 0.1-0.3% of organosilicon emulsion, and ceramic granules - the rest. Granules are finally cooled. Organosilicon emulsion is prepared at emulsion-to-water ratio 1:10.
EFFECT: increased strength of ceramic proppant and improved its quality due to resin coating applied with separating emulsion.
2 cl, 1 dwg, 1 tbl, 2 ex
FIELD: oil and gas production.
SUBSTANCE: fluid contains, wt %: industrial-grade powdered lignosulfonates 26.4-31.7, potassium chloride 4.9-5.9, aluminum sulfate 1.2-1.50, borax 0.4-0.5, formation water 40.3-44.7, and sweet water in proportion to formation water as 1:(1.98-1.99).
EFFECT: improved process parameters due to improved structurally mechanical properties of fluid, raised viscosity thereof, high sand-retention ability, and possibility of controlling lifetime without loss in high technological characteristics.
1 tbl, 2 ex
FIELD: oil and gas production.
SUBSTANCE: in a method of preparing propping agent including grinding, hydration, molding, drying, and calcinations of raw material, the latter is natural bentonite clay containing more than 90% montmorillonite, molding of spherical granules of propping agent 200 to 400 μm and 420 to 850 μm in size involves spray drying technique and molding of granules more than 850 μm in size is accomplished using beading process, and calcinations is carried out at 600-650°C. Method is applicable for use in intensification of oil and gas inflow from producing beds.
EFFECT: reduced expenses of hydraulic fracturing of formation.
FIELD: oil and gas production.
SUBSTANCE: invention relates to production of proppants, i.e. splitting granules, used in oil and gas production via breakdown way. Proppant of invention is obtained from caked two-component aluminosilicate fees in the form of granules with density 2.2-3.0 g/cm3 and 0.2-2.5 mm in size consisting of nucleus and shell, wherein one of components of aluminosilicate feed, which forms granule nucleus is a low-alumina substance containing less than 30% of alumina: coal combustion ashes, preliminarily fired kaolin, nepheline, nepheline syenite, feldspar, shale, or alumina production slime waste, and other component of aluminosilicate feed, which forms granule shell, is a high-alumina substance containing above 70% alumina: alumina dust of electrofilters of aluminum hydroxide calcination furnaces, industrial alumina, preliminarily fired bauxite, and exhausted catalysts based on active alumina form. Feed contains 50.0-95.0% low-alumina substance and 5.0-50.0% high-alumina component. In a method for production of proppant from two-component feed including (i) granulation upon addition of binding component in mixer-granulator provided with plate cup rotating at constant speed and rotor-type stirrer whose rotation speed is varied in dependence of granulation stage, (ii) drying, (iii) sizing of fried granules, (iv) firing of granules in rotary furnace, and (v) sizing of fired granules to form commercial fractions, when obtaining above-indicated proppant, low-alumina substance is used in the first granulation stage and, after granules 0.15-2.0 mm in size are formed, second granulation stage comprises addition of high-alumina substance into granulator followed by further granulation until granules 0.2-2.5 mm in size are obtained. Preliminary firing of low-alumina substance (as defined above) is carried out at 700-1200°C and the same of high-alumina substance (as defined above) at 700-1400°C. Firing of dried granules id effected at 1100-1600°C. Binding substance is used in the form of aqueous suspension of an organic binder (carboxymethylcellulose, methylcellulose, low-grade lignosulfates) of aqueous suspension of clay, wherein concentration of suspended binder is 1.0-10.0%. Aqueous suspension is added during granulation process in amounts 10.0 to 40.0% of the weight of initial feed.
EFFECT: enabled production of proppants from accessible raw materials (production wastes) without complication of existent technology.
9 cl, 1 tbl, 14 ex
FIELD: oil production from drill-holes, particularly to stimulate productive beds by bed drainage and formation fluid filtering channel forming.
SUBSTANCE: method involves forming at least one opened horizontal well bore or one opened horizontal well bore with at least one opened side branch bore extending along the strike in productive area thereof; filling the bore with hydrophobic granular material, wherein bore and branch bore filling is performed in portions along with compacting each portion of granular material up to material subsidence and existent natural bed cracks opening under the action of material compaction; installing and fixing filtering unit in well bore. Device comprises sectional or continuous pipe string, conical flared body fixedly secured to pipe string. Arranged in the body is system including pusher with central through channel and with cone. The pusher is hung inside the body and connected to cylindrical spring so that the pusher may be axially displaced and perform self-oscillations. Flared body and pusher cone are axially joined and form valve couple. Freely sliding impact bush is located over pusher anvil.
EFFECT: increased hydrocarbon material output and increased oil and gas recovery factors.
4 cl, 1 ex, 3 dwg
FIELD: mining, particularly to weaken coal bed and to increase recovery of desorbed methane.
SUBSTANCE: method involves drilling well from well surface; casing the well; exposing coal bed; injecting working liquid in the coal bed, wherein the working liquid has pressure enough to perform hydraulic fracturing of the bed and flow rate providing elongated crack forming. Salt solution, gel with propane or gel decomposition substance are used as the working liquid. Propane content in gel is gradually increased from 50-100 kg/m3 to 500-600 kg/m3 as cracks are formed and fixed. The salt is potassium chloride or propant having particle diameters of 20-40 meshes. Coal bed exposing is performed by cutting casing pipe and cement ring in central bed zone within interval of 100 mm so that the ready hole has height of 50-100 mm. The coal bed may be also opened by coal bed drilling below casing pipe for depth of 50-100 mm.
EFFECT: increased formation weakening and increased methane recovery.
3 cl, 2 ex
FIELD: technology for increasing recovery of hydrocarbons from foliate geological formations, which contain absorbed condensed gaseous hydrocarbons, by processing such geological formations with dehydrating compositions, containing surfactants, which cause dampening of geological formation with oil or leave aforementioned formations dampened with oil.
SUBSTANCE: methods may be used for excitation of influx of fluid substance from geological formation into well, or hydro-acid fracture, or hydraulic fracture, during maintenance or major repairs and when increasing influx from natural cracks or from geological formations never subjected to influx stimulation.
EFFECT: increased water removal efficiency, minimization of migration of low dispersion particles, increased extraction of hydrocarbons from underground formations, containing absorbed and compressed gaseous hydrocarbons.
3 cl, 4 ex, 6 tbl
FIELD: measuring technique.
SUBSTANCE: method comprises allowing the main liquid to flow through the Coriolis flow meter, measuring the density of the main liquid, and transmitting the signal containing measured value of the signal to the control system, adding the filler to the main liquid, allowing the mixture to flow through the Coriolis flow meter, and transmitting the measured value of density to the control system.
EFFECT: enhanced accuracy.
19 cl, 5 dwg
FIELD: manufacture of granulated materials used as wedging filler and gravel filter for control of sand flow.
SUBSTANCE: proposed granulated material has particles coated with two or more layers of hardenable coat; coated particles include granulated substrate and at least one layer of first curable resin practically embracing the substrate and at least one layer of second curable resin practically surrounding at least one layer of first curable resin; amount of curing agent in layer of first curable resin and in layer of second curable resin is lesser than that at which resin is practically cured.
EFFECT: increased compressive strength; increased elasticity; high strength at curing; forming strong blocks of wedging filler at pumping granulated material into well.
86 cl, 1 dwg, 12 tbl