RU2209302C2 - Method of development of oil deposit at late stage - Google Patents

Abstract

FIELD: oil and gas producing industry, particularly, methods of oil recovery from nonuniform water- encroached formations at late stage of oil deposit development. SUBSTANCE: method includes injection into formation through injection well of aqueous solutions of reagents forming insoluble precipitate. One reagent is used in form of metal chloride. Ratio of injected reagents is taken in compliance with stoichiometric coefficients ensuring maximum yield of precipitate. Oil production is carried out through producing well. Injection of reagent aqueous solutions is effected successively or concurrently. Metal chloride is used in form of one component of the following group; calcium chloride, magnesium chloride, aluminum chloride, iron chloride. The other reagent is used in form of salt of polybasic acid or alkali. In addition, introduced together with solution of salts is water repellant. Concentration of reagents in solutions is selected proceeding from geological and physical characteristics of formation. To obtain precipitate in form of metal hydroxide, the other reagent is used in form of sodium or potassium hydroxide. Water repellant is used in form of water-soluble organosilicon compounds or anionic surfactants with concentration of 0.5-5%. EFFECT: provided water shutoff barriers with improved process parameters and increased duration of effect for formation zones with any permeability, extended assortment of chemical reagents applicable in method realization. 3 cl, 2 tbl

Description

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

 There is a method of developing a flooded oil reservoir, the essence of which is to inject into the reservoir through an injection well an aqueous solution of aluminum chloride followed by injection of an alkaline solution [1].

 The disadvantage of this method is the short duration of the effect, since subsequent injection of the displacing agent causes erosion and displacement of the sediment.

 The closest solution taken as a prototype is a method of isolating the influx of formation water, which includes the sequential injection into the reservoir of salts of polybasic acid and salts of alkaline earth metals in the form of a solution or suspension [2].

 The disadvantage of this method is the limited application of it on the permeability of the collectors and the insufficient duration of the effect due to the low resistance of the insulating screen to erosion.

 The objective of the invention is to provide a method for developing waterlogged oil fields at a late stage of operation by creating insulating screens with improved technological parameters and with an increase in the duration of the effect for formation zones with any permeability, as well as expanding the range of chemicals in the implementation of the proposed method.

 The problem is solved in that in a method of developing an oil reservoir at a late stage, which involves injecting into the formation through an injection well aqueous solutions of reagents forming an insoluble sediment, while metal chloride is injected as one reagent, the ratio of injected reagents is taken in accordance with stoichiometric coefficients, providing the greatest yield of sediment, and oil production through a production well, according to the invention, the injection of aqueous reagent solutions is carried out by a follower o or at the same time, one component from the group is used as metal chloride: calcium chloride, magnesium chloride, aluminum chloride, iron chloride, as another reagent - a salt of polybasic acid or alkali, in addition, a water repellent is additionally added with a solution of salts, and the concentration of reagents in solutions are selected based on the geological and physical characteristics of the reservoir.

 To obtain a precipitate in the form of a metal hydroxide, alkali in the form of sodium or potassium hydroxide is used as another reagent. As a water repellent agent, water-soluble organosilicon compounds or anionic surfactants with a concentration of 0.5-5% are used.

 The essence of the invention lies in the fact that solutions of reacting salts and alkalis are taken in a ratio that ensures maximum formation of sediment in the reservoir.

 Table 1 presents examples of specific reactions, taking into account the ratio of reacting substances, according to stoichiometric coefficients, providing the maximum yield of sediment. In order for the insulating screen to cover the formation more fully, both in terms of the thickness of the formation and along strike, it is necessary to use solutions with appropriate concentrations of reagents, and to protect the screen from erosion, the solutions must contain a hydrophobizing reagent.

 The hydrophobization of the screen is achieved by the addition of water repellents in metal chloride solutions. Water repellents are adsorbed on the surface of the rock outward by a hydrocarbon radical, as a result of the rock and particles of the precipitate formed become hydrophobic, make it difficult to filter water due to increased capillary pressure and prevent erosion of the screen.

 This action is mainly possessed by anionic surfactants (alkylarylsulfonates, petroleum sulfonates, etc.) or cationic substances (organosilicon compounds, quaternary ammonium salts) and cationic surfactants having high adsorption capacity on the rock surface.

 Table 2 shows the concentration of the solutions, taking into account the permeability (injectivity) of the formation.

 In the case of heterogeneity of the formation, it is recommended to pump in individual rims, starting from low concentrations, gradually increasing the concentration during the injection of subsequent rims.

 In field conditions, the process according to the proposed method is as follows.

To align the injectivity profile of the BV ₁₀ formation of the Tyumen field, with a permeability heterogeneity of 50 μm ² to 250 μm ² , a solution of aluminum chloride (AlCl ₃ ) and soda ash (Na ₂ CO ₃ ) was used.

 The work was carried out using standard equipment.

In order to isolate the low-permeable part of the formation according to table 2 for a permeability of 50 μm ^{2, the} first rim is injected with a concentration of reagents of 1.5%, the second rim for permeability of 50-100 μm ² has a concentration of reagents of 2.5%. The third rim with a concentration of reagents 5% for a permeability of 250 μm ² additionally contains a water repellent 1.5% GKZH-10. The consumption of reagents is taken in a ratio of 1: 0.8, i.e. 1 m _AlCl3 take 0.8 m Na ₂ CO _3, forming a precipitate of 0.8 m in the form of aluminum hydroxide.

 Solutions of aluminum chloride (with the addition of a water repellent) and soda ash are prepared separately in the tanks of two cementing aggregates, which are used as pumps when pumped. Solutions are injected simultaneously or sequentially depending on the injectivity of the formations. At the end of the injection of the required volume of reagents, the well is launched under injection.

 The proposed method allows to increase oil recovery due to the involvement in the development of previously unreached sections of the reservoir, as a result of creating an insulating screen that is resistant to erosion and, therefore, ensuring the duration of the effect.

Sources of information:
1. RF patent 2039224, cl. E 21 B 43/24, 1994.

 2. RF patent 2108455, cl. E 21 In 43/32, 1998 (prototype).

Claims (3)

 1. A method of developing an oil reservoir at a late stage, which involves injecting into the formation through an injection well aqueous solutions of reagents forming an insoluble precipitate, metal chloride being pumped as one reagent, the ratio of injected reagents is taken in accordance with stoichiometric coefficients, which provide the highest yield of sediment, and oil production through a production well, characterized in that the injection of aqueous reagent solutions is carried out sequentially or simultaneously, as chloride metal, one component from the group is used: calcium chloride, magnesium chloride, aluminum chloride, iron chloride; as another reagent, a polybasic acid salt or alkali; in addition, a hydrophobizing agent is additionally added with a solution of salts, and the concentration of reagents in the solutions is selected based on the geological physical characteristics of the reservoir.  2. The method according to p. 1, characterized in that to obtain a precipitate in the form of a metal hydroxide, alkali in the form of sodium or potassium hydroxide is used as another reagent.  3. The method according to claim 1, characterized in that water-soluble organosilicon compounds or anionic surfactants with a concentration of 0.5-5% are used as a hydrophobizing agent.

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