RU2117143C1 - Method for development of oil deposit - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: method is aimed at involving low-permeable oil-saturated sections of bed in developing activities and increasing their producing capacity. According to method, simultaneously injected into oil bed through injection well are polymer solution and water solution of alkali. Then injected is water solution of salt of polyvalent metal, and additionally pumped in is water solution of calcium chloride. This is performed prior to injection of displacing agent. EFFECT: higher efficiency. 3 cl, 2 tbl

Description

 The invention relates to the oil industry, in particular to methods for oil production from heterogeneous formations at a late stage of oil field development.

 A known method of developing oil fields, including the injection through injection wells of aqueous solutions containing polyacrylamide, bentonite clay and water [1].

 The disadvantage of this method is the low efficiency in the isolation of washed zones if the reservoir is represented by a highly permeable fracture-pore reservoir, since the "crosslinking" of PAA type polymers and clay does not occur without preliminary hydrolysis by alkali, therefore, the polymer remains "not crosslinked" soluble in water and displaced by the injected agent.

 The closest in technical essence and the achieved result is a method of developing an irrigated oil reservoir, which includes the sequential injection of caprolactam (ALSCP) production of aluminum chloride and alkaline effluents into the injection well [2].

 The disadvantage of this method is the low tamping ability of the composition, which leads to ineffective isolation of the washed zones of the formation, due to the fact that the used SCHSC waste, which is the sodium salt of adipic acid, is used only for the formation of aluminum hydroxide, while adipic acid itself leaves with the formation fluid and does not used for extra insulation.

 The objective of the invention is to increase the efficiency of the method of developing an oil deposit by layer-by-layer plugging of washed and highly permeable flooded formations by increasing the amount of sediment and, as a result, involving low-permeable oil-saturated sections of the reservoir in the development and increasing their oil recovery.

 The stated technical problem is solved by the fact that in the method, which includes injecting an aqueous solution of a multivalent metal salt, an aqueous solution of alkali into the formation through an injection well and then injecting a displacing agent, a polymer solution and an aqueous solution of alkali are simultaneously injected into the formation at the same time, and before by injection of the displacing agent, an aqueous solution of calcium chloride is additionally pumped into the formation, while water is used as an aqueous solution of a multivalent metal salt aluminum sulfate solution, water-soluble PAA or CMC polymers are used as a polymer solution, and caustic or calcined soda or an aqueous solution of caprolactam alkaline runoff are used as an aqueous alkali solution.

 To implement the technology used technical products manufactured by industry in large volumes.

 Water soluble polymers of class PAA and CMC. - polyacrylamide and carboxymethyl cellulose.

 As the salt of the multivalent metal, aluminum sulfate is used according to GOST 3758 - 75.

Calcium chloride is supplied in dry form GOST 450 - 77 or in the form of a saturated solution with a density of 1320 - 1350 kg / m ³ TU - 48 - 10 - 509 - 78.

 Caustic soda GOST 2263-79, soda ash GOST 5100 - 73 or alkali metal salts of organic acids are used as alkali solution - a waste product of caprolactam production SCHSPK - TU 113 - 03 - 488 - 84.

 The essence of the invention is as follows. Polyacrylamide or CMC and an alkali solution are simultaneously pumped into the reservoir through an injection well.

 In the interaction of an aqueous polymer solution with an alkaline solution, hydrolysis of the amide groups occurs.

 Hydrolyzed polymer has a viscosity of 20-30 cP, but it does not lose its ability to dissolve in water. When injecting a solution having a viscosity of 20-30 cP, an increased filtration resistance is created and thereby the formation coverage is increased by exposure.

Next, a solution of a salt of a multivalent metal is pumped. During the interaction of the hydrolyzed polymer with aluminum sulfate (ferrous sulfate), the polymer is “crosslinked” with a trivalent aluminum cation (Al ³⁺ ) and an aluminum hydroxide precipitate is formed, while the solution contains a large amount of SO ions $\genfrac{}{}{0ex}{}{\text{-2}}{\text{4}}$ .

To increase the volume of sediment, a solution of calcium chloride CaCl _{2 is} injected, which, when reacted with sulfate ion SO $\genfrac{}{}{0ex}{}{\text{-2}}{\text{4}}$ forms a water-insoluble gypsum precipitate CaSO ₄ additionally plugging the pore space of the washed zone of the formation, increasing the filtration resistance of the injected agent and thereby increasing the coverage of the formation by exposure.

 This will form a precipitate consisting of a "crosslinked" polymer, aluminum hydroxide and gypsum.

 As a displacing agent, water or an aqueous surfactant solution is used.

With small injectivity values of the treated wells up to 150 - 250 m ³ / day, water-soluble polymers are not pre-hydrolyzed with an alkaline reagent, but are pumped in an aqueous solution of aluminum sulfate (iron sulfate) with subsequent injection of a solution of alkali and calcium chloride, which ensures the formation of a coarse precipitate in the formation, having high adhesion to the formation rock, in the future, after displacement of the reaction medium by injected water, PAA (CMC) swells, which, having flocculating properties, allows yaet "bind" formed separate dispersed particles of aluminum hydroxide and gypsum with each other and rock formation and thereby reduce the permeability of cracks and large pores.

 The reacted filtrate has an alkalinity of pH 9-10 and, when interacting with the acidic components of oil, leads to a decrease in interfacial tension at the oil-alkali solution interface. In this case, oil is emulsified and the wettability of the rock is improved, that is, residual oil is washed out.

 Laboratory studies to determine the amount of plugging sediment for the implementation of the proposed method are presented in table. one.

 From the results of the table. 1 it can be seen that the formation of the greatest amount of "crosslinked" polymer occurs during the interaction of solutions of PAA, alkali hydrogen sulfide and aluminum sulfate.

 The amount of clogging sediment according to the proposed method is 2-3 times greater than the prototype, even in the case of using highly concentrated solutions (experiment 3).

The resulting precipitate is resistant to temperatures in the range of 20 - 100 ^o C, as well as to the action of weakly acidic and slightly alkaline environments. When interacting with formation water, the sediment becomes more resistant to temperature effects.

The filtrate in its composition is close to formation water, since NaCl and traces of HCO remain in the solution $\genfrac{}{}{0ex}{}{\text{2-}}{\text{3}}$ .

 To determine the clogging properties of materials and the subsequent displacement of oil by the proposed technology, the laboratory conducted studies on artificial linear models with a length of 110 - 120 mm, a diameter of 30 - 40 mm. The studies were carried out according to generally accepted methods.

 The research results are presented in table. 2, which shows that the insulation coefficient in experiments 4-5 on the proposed technology is significantly higher than on the prototype (experiment 1 - 2).

 When implementing the method at the field, injection is carried out into one or more injection wells.

At the same time, 20 - 25 m ^{3 of a} 0.5% PAA solution and the same volume of a 25% solution of SchSPK are pumped into the well. After the two-hour exposure necessary for the hydrolysis of polyacrylamide, a 10% solution of aluminum sulfate is pumped into the formation. The solution is pushed through with 10 m ^{3 of} water and then 20 - 30 m ^{2 of a} 10% solution of calcium chloride is pumped into the formation.

 Then a displacing agent is injected, which is used as water or an aqueous solution of a nonionic or anionic surfactant.

 To implement the technology using standard equipment. Reagents can be injected in cycles 1. Each subsequent cycle is similar to the first cycle.

The optimal injection volume of these solutions is determined by generally accepted methods, based on the physicochemical and geological features of the formation, and may be 40-200 m ³ .

 The proposed method allows to increase oil recovery, heterogeneous in geological structure at a late stage of development, due to the alignment of the injectivity profile with subsequent alkaline exposure.

Claims (4)

 1. A method of developing an oil deposit, which includes injecting an aqueous solution of a multivalent metal salt, an aqueous alkali solution into the formation through an injection well, followed by injection of a displacing agent, characterized in that both the polymer solution and the alkali aqueous solution are simultaneously injected into the formation before the aqueous solution of the multivalent metal salt is injected and, before injection of the displacing agent, an aqueous solution of calcium chloride is additionally pumped into the formation.  2. The method according to claim 1, characterized in that an aqueous solution of aluminum sulfate is used as an aqueous solution of a salt of a multivalent metal.  3. The method according to claim 1, characterized in that as the polymer solution using water-soluble polymers polyacrylamide or carboxymethyl cellulose.  4. The method according to claim 1, characterized in that as an aqueous solution of alkali using caustic soda, or calcined, or an aqueous solution of alkaline runoff production of caprolactam.

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