Process fluid for drilling, completion and repair of oil and gas wells under conditions of abnormally high formation pressures and elevated temperatures

 

The invention relates to the construction of oil and gas wells and oil production, namely to the process fluids used in well construction, completion and workover under conditions of abnormally high formation pressures and high temperatures. The purpose of the invention is the improvement of thermostability weighted process fluids up to +200oWith simultaneous reduction of negative physical and chemical effects on the producing formation by preventing the formation of insoluble residues and emulsions. The technical result is achieved by the process fluid for drilling, completion and repair of oil and gas wells under conditions of abnormally high formation pressures and elevated temperatures containing polysaccharide reagent or a mixture of polysaccharide reagents, weight and water as a filler it contains a salt of formic acid alkali metal in the following ratio of ingredients, wt.%: polysaccharide reagent or a mixture of polysaccharide reagents of 0.1 to 7.0, salt of formic acid alkali metal 45,0-83,0, water - the rest. The fluid may further comprise complex crosslinking agent from neola which contains acid-soluble weighting agent, for example carbonate flour, crumbs, in the amount of 2-50. 2 C.p. f-crystals, 2 tab.

The invention relates to the construction of oil and gas wells and oil production, namely to the process fluids used in well construction, completion and workover under conditions of abnormally high formation pressures (AHP) and high temperatures. These fluids are used in the construction of wells as drilling mud; while jamming wells as well kill fluid, the second opening as the fluid perforation and development; fracturing - as fracturing fluids and fluid-desconocidas.

Currently, one of the problems in the construction and workover is to develop environmentally safe process fluids for abnormal conditions and high formation temperatures. The necessity of such liquids is due to a number of geological and technical factors, such as high gradient formation pressure, the presence in the context of unstable rocks prone to rockslides and avalanches, to sustain, require a fairly high protevtive is in abnormal conditions and elevated reservoir temperatures is the use of process fluids with high values of fluid density, stable under thermodynamic influence of rheological and filtration properties.

The process liquid must have a high any abscopal and gidrofobiziruyuschimi properties in relation to clayey rocks of the borehole wall, and clay cement collector, preventing their swelling and dispersion throughout the period of technological operations in the well.

In addition, the reagents included in such process fluids and forming colmatage screen in the bottomhole formation zone, should be easy to collapse under the influence of simple chemical treatments, or chemical exposure.

Currently, domestic and foreign practice as such agents are used polysaccharide reagents and the acid-soluble bridging agents (starch, biopolymers, cellulose ethers, carbonate weighting agent).

To increase the density of the known process fluids used produced water, solutions of inorganic salts (chlorides of sodium, potassium, calcium, magnesium), calcium carbonate. The use of these weighting additives can obtain the density of a liquid 1180-1360 kg/m3. To obtain a more well-Known high-technology-based liquid AMMONIATING solution of calcium nitrite for completion and repair of wells under conditions of elevated temperatures (1). Known process fluid has a density of 1600 kg/m3and thermostability over 100oWith that it is a positive quality.

However, if you contact her with formation waters of the shift occurs (violation) bicarbonate or sulfate equilibrium process fluid towards the formation of carbonate or sulfate, or calcium carbonate according to the scheme:In these a result of the processes of asadharana significantly reduced weight, the effect of this known fluid. However, the decisive factor among the disadvantages of this fluid is its environmental insecurity, because nitrate when heated decompose to form nitrites.

Known also non-clay drilling mud containing magnesium chloride, caustic magnesia, phosphoric acid, starch, calcium bromide and water in the following ratio of ingredients, wt.%: magnesium chloride 4,5-13,0; caustic magnesite 0.5 to 2.0; phosphoric acid 0,5-1,0; starch from 0.3 to 1.0; calcium bromide 34,0-59,0; water - other (2).

Specified known drilling mud at a molar ratio of calcium ions to magnesium ions as 1,8:6,0 has a density 1450-1970 kg/m3and low znaczkow decrease the solubility of the salts of calcium and magnesium. By reducing this ratio less than 1.8 formed free magnesium ions disrupt the structured packing is known drilling mud, which increases the rate of filtration. The upper limit of calcium bromide is limited by its solubility in the system.

The disadvantage of this known solution is the difficulty of controlling performance properties, especially in field conditions, because when a slight deviation of the ratio of calcium ions and magnesium in one direction or another already there is a sharp change in performance properties. Also known composition is a multicomponent that in field conditions significantly complicates the process of its preparation.

Also, a significant disadvantage of this solution is the lack of stability (no more than 85oC). In addition, the compounds of bromine, are included in it, from the point of view of ecology unsafe.

Also known process fluid for plugging wells containing starch, weight (bromides of calcium and zinc) and water in the following ratio of components: starch 1-3%, calcium bromide 43-52% and bromide zinc 19-28%, water - other (see, for example, "Theory and practice completion wells shall pokazateli and low thermal stability. In addition, the interaction of a known composition containing salts of calcium and magnesium, with formation fluids (oil, formation water) is sludge formation and oil-water emulsions.

The closest in purpose and technical nature of the present invention is a weighted non-clay process liquid for operations under conditions of abnormally high pressure and elevated temperatures, containing water, a mixture of polysaccharide polymers, namely heteropolysaccharide (biopolymer) 0,072-0,714%, and the modified starch of 0.015 to 3.0%; stabilizing additive is magnesium oxide of 0.05-1.5% and a water-soluble salt of one or divalent metal is not less than 1.0%, for example sea water with additional content of sodium chloride or potassium, or calcium, and added to this mixture weighting in number 76-92 g/l of a mixture of [4]. As the primary weighting component known liquid contains a water-insoluble salt is barium sulfate (barite), lead oxide (PbO or Pb3O4), iron oxide, calcium carbonate. Specified known liquid has a high thixotropic properties, sufficient to ensure the sedimentation stability of weighted vodorastvorimami salts by tehnologicheskih.html known liquid is not sufficiently high thermal stability (no more than +95oC). In addition, the composition contains a water-insoluble salt, which leads to irreversible contamination of bottom-hole zone of the reservoir.

The technical result achieved by the invention is to improve thermal stability of the weighted process fluids up to +200oWith simultaneous reduction of negative physical and chemical effects on the producing formation by preventing the formation of insoluble residues and emulsions.

An additional aim of the invention is to improve the environmental fluid.

This technical result is ensured by the process fluid for drilling, completion and repair of oil and gas wells under conditions of abnormally high formation pressures and elevated temperatures containing polysaccharide reagent or a mixture of polysaccharide reagents, weight and water as a filler it contains a salt of formic acid alkali metal in the following ratio of ingredients, wt. %: Polysaccharide reagent or a mixture of polysaccharide reagents 0.1 to 7.0 G of formic acid alkali metal - 45,0-83,0 Water - the Rest With the liquid can the x metals and alkaline pH regulator in an amount of 0.1-2.0 wt.%.

In addition, it can optionally contain acid-soluble weighting agent such as carbonate flour, crumbs in the amount of 2-50 wt.%.

The achievement of a technical problem of the invention is ensured thanks to the unexpected property of salts of formic acid alkali metal to provide hydration (condensation) polysaccharide reagents without prior hydrating polymers in fresh or alkaline environment.

Alkali metal salts of formic acid dissociate with the formation of formic acid (HCOOH), which can be characterized and how the aldehyde, and as the acid, and as a functional group is a carbonyl group (N-C=O) and hydroxyl group (-OH).

Apparently, modifying macromolecules of polysaccharides occurs aldehyde group of formic acid, for which the most characteristic reactions of addition of various substances and formation of hydrogen bonds with hydroxyl groups, for example polysaccharide reagents.

As a result of these processes is, for example, gelatinization insoluble in cold water starch or other hydration water-soluble polysaccharide reagents.

The presence in the inventive composition is of hentov to thermal-oxidative and enzymatic degradation.

When this ingredient ratio of the new process liquid has a wide range of rheological properties (viscosity of water to the viscoelastic properties of the body) and adjustable rate of filtration (to a minimum of 0.2-0.5P=0.7 MPa).

To receive the process liquid with extremely high structural properties (e.g., a viscoelastic composition for temporary isolation of the productive formation at killing of wells) along with polysaccharide reagents and salt of formic acid are integrated, cross-linking agents from among inorganic salts, one -, two-, and trivalent metals, such as alkali metal borate, or copper sulfate, or potassium (chromolaena) alum and alkaline pH regulator such as sodium hydroxide, potassium or sodium silicate, metasilicate sodium.

For preparation of the inventive composition in the laboratory were used the following substances.

The modified starch, THE 9187-012-53501222-2000.

Polyanionic cellulose brand Celpol RX or Expacom Ltd, THE 2231-015-53501222-2001.

Biopolymer brand Rhodopol 23P or, Bovis etc.

Sodium formiate, THE 2432-011-00203803-98.

The potassium formate imported.

The cesium formate.potassium Dubrovskiy, GOST 4220-75;
chromecacheview alum, GOST 4162-79 ISM.1.

Alkaline pH regulators:
sodium hydroxide or potassium TU 6-01-204-847-06-90;
sodium silicate, metasilicate sodium TU 2145-018-53501222-2001;
carbonate weighting agent, GOST 14050-93.

The essence of the invention is illustrated by the following examples.

Example 1. To obtain the claimed process fluid that is used as drilling mud, to 238 mg technical water was added to 750 g of potassium formate, and the mixture was stirred for 0.2 h, then added 10 g of potato starch and 2 g polyanionic cellulose mark Expacom Ltd, was stirred for 1.0 h at laboratory stirrer and received a composition with the following composition of ingredients, wt.%: starch - 1.0; potassium formate - 75; polyanionic cellulose is 0.2; water - 23,8 (corresponds to composition 2, PL.1).

Example 2. To obtain the claimed process fluid that is used as the viscoelastic composition in the killing of wells, to 305 mg technical water was added 660 g of potassium formate, mixed for 0.2 h, and then added 20 g polyanionic cellulose, mixed 1.5 h, then brought to 15 g of compound cross-linking reagent and mixed with 0.1 dannym composition, wt.%: the potassium formate - 66,0; polyanionic cellulose - 2,0; integrated cross-linking reagent 1,5; water - 30,5 (corresponds to part 8, PL.1).

Similarly prepared other compounds of the claimed process fluid for various purposes with different ratio of ingredients.

Data on the composition of the investigated process fluids are given in table.1.

In the laboratory analyzed the following performance properties of the inventive and well-known prototype process liquids:
- the rate of filtration (f, cm3when the differential pressure of 0.7 MPa), measured on a dynamic filter press company OFI;
- rheological properties plastic viscosity (MPaC) and dynamic shear stress (0, DPA) measured on a viscometer company OFI);
- dynamic viscosity (PA) measured by the viscometer of Hepler, only for viscoelastic compositions (table. 1, 2 compounds 8, 9);
- index pseudoplasticity n and consistency index "K" was calculated by the well-known formulas (see , for example, J. R. gray, G. S., Darley "Composition and properties of drilling agents (drilling fluids) ". -M.: Nedra, 1985, page 99;
- pH (istii process fluid with the oil examined by the following method. The beaker was poured 80 cm3the test composition (known or claimed) and 20 cm3oil (oil for the study was taken from Yasnaya Polyana horizon char field with the following parameters:=944 kg/m3; dynamic viscosity is 76.9 SDRs; cut - to 22.0%, the content of asphaltenes, resins and waxes respectively 3,17%, 15,92%, 3,69%), the mixture was mixed in a laboratory mixer for 30 min with a speed of 1000 Rev/min Then the mixture was poured into the measuring cylinder 100 cm3after 30 min measured volumetric content of VNE. The results are shown in table.2 (9th column). In compounds 8, 9 this parameter is not measured, because the mixing process fluid (MAS) with the oil does not occur;
thermal stability was studied by dynamic filter press high temperature and high pressure company OFI at a temperature of +200oC for 6 hours In modifying the parameters of the process liquid before and after heating was judged on its thermostability.

In table.2 shows data about the performance properties of process fluids.

With a stated ingredient ratio of the new process liquid has a wide range of rheological its vesennih temperatures (up to +200o).

The data in the table.1-2 show that the claimed process fluid are:
- high density 2300 kg/m3;
- a wide range of rheological characteristics of plastic viscosity of 1.5 to 120 MPaand dynamic shear stress 3-700 DPA; dynamic viscosity of more than 1020 PA (measured only for viscoelastic compositions used in completion and workover);
- low rate of filtration at a pressure drop ofP=0.7 MPa 0.2 to 4.8 cm3.

The process liquid having the same composition but different mass ratio of ingredients, may be an indicator of pseudoplasticity greater than 1, i.e., to obey the rheological laws diletantes liquid, or significantly less than 1 and have rheological condition that may be characterized by gipertsiklicheskie. It should be noted that in all these conditions, the coefficient of consistency of such liquids remains quite low, which positively affects their Sipper ability.

These technical advantages of the claimed process fluid to:

1. To improve thermal stability (heat-resistant is in decline filtering, that will allow to carry out work on the construction and repair of wells not only in terms of complicated pore pressure prediction, but with higher temperatures.

2. To improve the sustainability of process fluid due to its high thermal stability, i.e., when the temperature rises above 100odoes not occur decomposition of the liquid composition remains unchanged technological parameters.

3. To reduce the negative impact on the productive formations due to low filtering the claimed process fluid, and hence the low penetrating power of the solution due to the ability of the liquid does not form a water-oil emulsion and insoluble precipitates upon contact with formation fluids.

Sources of information
1. The dissertation on competition of a scientific degree of candidate of technical Sciences Rabic N. To. "Development of high-density fluids based AMMONIATING solution of calcium nitrate for completions and workover at high temperatures with a high level of productive layers", Krasnodar, 1997

2. A. C. the USSR 1357420, class C 09 K 7/02, 1987

3. Theory and practice of completion: 5 t / Ed. by A. I. Bulatov. - M.: JSC Publishing house in the and inventions

1. Process fluid for drilling, completion and repair of oil and gas wells under conditions of abnormally high formation pressures and elevated temperatures containing polysaccharide reagent or a mixture of polysaccharide reagents, weight and water, characterized in that as a filler it contains a salt of formic acid alkali metal in the following ratio of ingredients, wt.%:
Polysaccharide reagent or a mixture of polysaccharide reagents - 0,1-7,0
Salt of formic acid alkali metal - 45,0-83,0
Water - the Rest
2. Fluid under item 1, characterized in that it further includes a crosslinking agent from among inorganic salts, one -, two-, and trivalent metals and alkaline pH regulator in an amount of 0.1-2.0 wt.%.

3. Fluid under item 1, characterized in that it further comprises acid-soluble weighting agent such as carbonate flour, crumbs, in the amount of 2-50 wt.%.

 

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FIELD: oil and gas production.

SUBSTANCE: water-based drilling mud contains, wt %: hydroxyethylcellulose or carboxymethylcellulose 0.2-0.3, petroleum product as structuring agent 5-30, alkylsulfonate-series surfactant0.02-0.05, powder-like high-dispersed filler 0.9-1, and additionally air or nitrogen 2-29 vol %.

EFFECT: reduced filtration and enabled penetration of drilling mud into highly fractured producing strata.

1 tbl, 7 ex

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