Composition for oil extraction from heterogeneous oil reservoir

 

The invention relates to the field of the oil industry, in particular to the extraction of oil from heterogeneous oil reservoir by injection of polymer solutions. Composition for oil extraction from heterogeneous oil reservoir, comprising a mixture of anionic polymer and a salt of polyvalent cation and water, contains water with salt content up to 280 g/l, and the mixture is equivalent to the specified cation for the anionic unit of the polymer is from 0.01 to 1.07 and pH 4-10 in the following ratio, wt.%: anionic polymer is 0.001 to 0.08; salt of polyvalent cation 0,0005-0,002; specified water - the rest. The technical result is to increase the efficiency of development of a heterogeneous oil reservoir by improving the rheological properties of the composition used, the expansion of the scope through the use of saline water and the simplification of the preparation of the composition due to the exclusion of alkalizing. table 2.

The invention relates to the field of the oil industry, in particular compositions for the production of oil from heterogeneous oil reservoir by injection of polymer solutions.

There is a method of extracting oil from oil complex heterogeneous is to increase oil recovery. - M.: Nedra, 1985, S. 156-165.).

The disadvantage of this method is its relatively low efficiency due to adsorption of the polymer and the destruction of its salty waters.

The closest to the technical nature of the present composition is an oil extraction method (A. S. 1645472, E 21 In 43/22, publ. B 16, 1991) by injection of the composition based on water-soluble anionic polymer and a salt of polyvalent cation in the following ratio, wt.%: Water-soluble anionic polymer is from 0.01 to 5.00 Salt of polyvalent cation - 0,003-0,20 Water - the Rest Additive salts of polyvalent cation leads to cross-linking of the polymer, which greatly improves its rheological properties.

However, the method involves the acidification of the polymer solution to a pH of 0.5 to 2.5 before the introduction of salts of polyvalent cation to improve its filtration properties. In the system containing a water-soluble anionic polymer type and a salt of polyvalent cation, acidified to pH less than 2.5, the polymer and the cation of the salt is not connected in a single complex, because the pH stitching anionic polymer does not occur, since the molecules of anionic polymer are in the ionized state. It is assumed that the motion of the structure will come cross-linking of the polymer.

However, simultaneously with the increase of pH in the reservoir will be a reduction of the initial concentrations of the components. In addition, when a certain pH can begin the hydrolysis of salts of polyvalent cation. For example, aluminium sulphate undergoes hydrolysis at a pH greater than or equal to 4 with the formation of aluminium hydroxide, insoluble in water. In this form it will not be able to participate in the linking of the polymer molecules.

In addition, there will be the adsorption of polymer molecules on the rock composing the layer. All of the above can lead not only to a decrease of the content of the polymer and salts of polyvalent cation in solution, but also to change their ratio compared to the original (injected into the reservoir) composition.

Thus, simultaneously with the process of increasing the pH of the solution will be exposed to other, competing with these processes, preventing in some cases, the formation of cross-linked system.

The basis for this assertion is provided by results obtained in laboratory studies.

The technical objective of the proposed solutions is to increase the effectiveness of the composition in the extraction of oil from heterogeneous oil reservoir by improving the filter is highlighted by the fact that the composition for the extraction of oil from heterogeneous oil reservoir, comprising a mixture of anionic polymer and a salt of polyvalent cation and water, contains water with salt content up to 280 g/l, and the mixture is equivalent to the specified cation for the anionic unit of the polymer is from 0.01 to 1.07 and pH 4-10, in the following ratio, wt.%: Anionic polymer is 0.001 to 0.08 Salt of polyvalent cation - 0,0005-0,002 Specified water - the Rest As shown by the comparison of the prototype and the proposed composition of the contents of the components, in particular the expensive polymer, in the proposed part 10 or more times less than in the prototype.

In addition to economic benefits, the reduction of the concentrations of the starting components provides a significant positive effect: unlike the prototype of the proposed structure does not require acidification to pH values of 0.5 to 2.5, which increases the efficiency of the structure by simplifying the technology of its application, improving the filtration properties of the composition and resistance to dilution with water.

When mixing a water-soluble anionic polymer and a salt of polyvalent cation in the above (homeopathic) quantities available macromolecules of the polymer is insufficient for entities such conditions are formed microglia particles, that can be represented in the form of capsules, average size of 0.85 and 0.35 μm. The inner part of such particles contain water (up to 50% of the total mass of such particles), and the shell consists of polymer molecules are connected to each other ("stitched") polyvalent cation.

Such polymer-gel capsules are freely suspended in the aqueous phase and not related to each other, as evidenced by the low values of dynamic viscosity of these systems, little different from the viscosity of polymer solutions containing no crosslinker. However, the viscoelastic properties of the dispersed polymer systems increased in some cases by several orders of magnitude.

Formed on the proposed composition of the polymer capsules can move deep into the layers of high permeability part of it to a considerable distance, gradually accumulate in large pores and isolating them. To penetrate the small pores or block them polymer capsules can't because of the larger size of its particles and low content in their water. This results in a redistribution filterable by reservoir oil-driving agent and the improvement of the production area of the oil reservoir and as a consequence enhanced oil recovery.

Predlagajetje anionic polyacrylamide Alcoflood-935 (Af) and Accotrol-S622 (At): the first of them is characterized by a low molecular weight (M m = 6.1 million D) and a low degree of hydrolysis (A=6,2 mol.%); the second high molecular weight polyacrylamide (M m=12.9 million D) with a high degree of hydrolysis (A=16,0 mol.%).

2. Aluminium sulphate (SKA) - A12(SO4)3N2O mark "analytical grade". The concentration in the preparation of solutions of aluminium sulphate was calculated from the original product.

3. Ferric chloride (MAM) - F136N2Oh, mark "h".

4. Water technical, mineralization of 0.5 g/l and waste, mineralization 100 and 280 g/L.

As a parameter of the filtration properties of the composition, characterizing the viscoelastic properties of polymer solutions, used screen size factor (SF), measured on a viscometer design Giprovostokneft according to standard methods (KMG-39-0148311-206-85).

Table 1 shows the values of dynamic viscosity and screen factor of the proposed structures.

As can be seen from the data, despite the low dynamic viscosity of the proposed formulations show good visco-elastic properties (in some cases, the compositions do not even filtered through the screen viscometer).

It was further studied by the us in table 2.

The analysis is shown in table 2 data allows to conclude that the proposed structure will withstand a large dilution of water - more than 250-fold). The compositions according to the prototype, which must be mixed to neutralize the acid, can not withstand much smaller dilution. If you compare the two composition is proposed and a prototype, you can see how much they differ in their viscoelastic properties in favor of the proposed structure.

Thus, studies clearly show the impact of the proposed structure and its advantages in comparison with the prototype.

Based on the conducted research, we can recommend the following concentrations of reagents: the polymer of 0.001 to 0.08% aluminum salts or iron 0,0005-0,002%.

The choice of the concentrations of the polymer and a salt of polyvalent metal was due to the following reasons. Its upper boundary of the receipt of a relatively homogeneous, kinetically and aggregately stable systems with the introduction of the polymer solution of salt of polyvalent metal. The lower concentration boundary - receiving effect, which consists in the improvement of technological properties of aqueous polymer systems from entry of schita.

In field conditions the composition is used as follows.

The area of the oil reservoir is represented by layers of different permeability and drilled at least one injection and one mining wells. Development of the site is maintained by pumping water from the pumping station.

Conduct a series of geophysical and hydrodynamic studies upon which to determine the concentration and volume of the rim composition based on a polymer and a salt of polyvalent metal. The composition is prepared on the surface: first prepare separately a solution of polymer injected with CND water and a solution of salts of aluminum or iron.

The polymer solution with the addition of the salt solution high-pressure pump serves in the conduit and the borehole. The salt solution is metered into a solution of polymer, based on the stoichiometric ratio to obtain the optimal concentration of cross-linked polymer. After injection of estimated quantity of composition in the well pumped water.

The composition was tested on a section of the Western-Leninogorsk the Romashkinskoye field with 8 injection wells located in the area of SPS-16. The plot presents layers "b1a ", "b2" and "b" horizon D1. Doba is agnatically the well was pumped to 2000 m3composition with PAA and aluminum sulfate. Used waste water salinity of 90 g/l with a pH of 5.5.

In the injection process, there was a gradual decrease in injectivity of injection wells, which indicates an increased filtration resistance layer. As a result, specific injection wells decreased on average 2 times.

Feasibility advantage of the proposed structure in comparison with the prototype is to reduce the consumption of expensive polymer while increasing the efficiency of its impact by improving the viscoelastic properties.

Claims

Composition for oil extraction from heterogeneous oil reservoir, comprising a mixture of anionic polymer and a salt of polyvalent cation and water, characterized in that it contains water with salt content up to 280 g/l, and the mixture is equivalent to the specified cation for the anionic unit of the polymer is from 0.01 to 1.07 and pH 4-10 in the following ratio, wt. %:
Anionic polymer is 0.001 to 0.08
Salt of polyvalent cation - 0,0005-0,002
The specified water - the Rest

 

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FIELD: oil and gas production.

SUBSTANCE: invention provides a method of developing oil pool allowing production of oil from water-rich oil reservoir under difficult geological-tectonic conditions in the last development stage. In the method, neutral salt of carbonic acid and acid solution are forced into formation through injecting well with water generated in gas-liquid fringe created in formation. After pumping of neutral salt of carbonic acid, acid solution is pumped by portions alternating with water pumping. Before pumping of acid solution portions beginning by at least second portion, selective insulation of high-permeable formation intervals is performed. Aforesaid neutral salt of carbonic acid utilized is sodium carbonate aqueous solution or aqueous suspension of calcium carbonate and aforesaid acid solution is aqueous hydrochloric acid solution. Selective insulation of high-permeable formation intervals involves use of freshly prepared controllable viscoelastic composition containing water-soluble acrylic polymer, cross-linking agent, thermal stabilizer, surfactant, and water. Summary concentration of acid solution is determined from concentration of neutral salt of carbonic acid on the base of stoichiometric proportions.

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SUBSTANCE: invention aims at increasing productivity of oil- and gas-producing and injecting wells exposing high-temperature low-permeable oil reservoirs. In the treatment method according to invention including forcing enzyme substrate and separate enzyme into formation and creating conditions to enzymatically convert substrate into acid, geologic and productive characteristics for each interval of bottom zone are determined in order to pick out low-permeable intervals of oil reservoir for treatment, whereupon properties of enzyme substrate and separate enzyme as well as conditions for their pumping are chosen. Substrate utilized in the method is head fraction of methyl- and/or ethyl-, and/or butyl acetate production, to which aliphatic alcohols are added, and enzyme is an acid solution. Substrate is pumped simultaneously and/or before, and/or after pumping of enzyme, after which well is closed for some time and then opened and placed under predetermined operational conditions.

EFFECT: enhanced efficiency of acid treatment due to increased phase permeability for oil and deepness of active acid-treated zone of low-permeable oil reservoirs.

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FIELD: oil and gas production.

SUBSTANCE: invention is intended for use during development of oil pools at different waterflooding phase for intensifying functioning of producing wells and increasing current oil recovery of formation. Composition contains, wt %: liquid hydrocarbon 10.0-20.0, oil-soluble surfactant 0.3-5.0, water-soluble or water-oil-soluble surfactant 0.1-1.0, superfine hydrophobic material 0.1-2.0, and water (the rest). Composition may further contain 0.3-5.0% calcium chloride. Oil recovery is increased owing to hydrophobization of formation structure, reduction of surface tension in water/rock/oil phase boundary, increase in detergent power of polluted surface, increase in composition viscosity, and increase of relative permeability of the formation for hydrocarbon phase as compared with water phase.

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2 cl, 2 tbl, 2 ex

FIELD: oil and gas production.

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2 tbl, 3 ex

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2 cl, 2 tbl

FIELD: oil and gas extractive industry.

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2 cl, 3 ex, 6 tbl, 2 dwg

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes placing water solution of carnallite ore, either modified, concentrated, or mixtures thereof, said solution is used at maximal for well temperature conditions concentration and is pumped in amount, necessary and enough for forming a hydraulic column in well shaft above ceiling of productive bed and along remaining shaft height well is filled with water up to mouth. Carnallite ore used has composition, in percents of mass: potassium chloride 20.5-21.5; sodium chloride 19.5-22.5; magnesium chloride 24.0-27.0; crystallization water 29.5-30.5. Modified ore has composition, in percents of mass: potassium chloride 23.0-29.5; magnesium chloride 31.8-46.0; crystallization water - the rest. Said water solution is prepared by dissolving ore in fresh technical water, drained from oil preparation plants, or in bed water. In case of dissolving in bed water, the latter is pumped from well at temperature 60-90°C. During perforation of well, value of technological liquid hydraulic column above productive bed ceiling is taken equal to (1.03-1.07)-(1.05-1.1)Pb, where Pb - productive bed pressure. Water solution of carnallite ore is used at density 1.23-1.37 t/m3. During use of said solution as working body of force wells it is used at density 1.05-1.20 t/m3, and solution also contains swelling inhibitor for argillaceous component of oil and gas bearing bed, like oxyethylenedendiphosphone acid, in amount 0.05-0.15% of used dissolved ore mass.

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EFFECT: higher efficiency.

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