RU2186958C1 - Method of isolation of formation high-permeability intervals - Google Patents

Abstract

FIELD: oil producing industry; particularly, methods of isolation of formation high-permeability intervals in injection and producing wells. SUBSTANCE: method includes successive injection in fresh water buffers of fringes of polymer-silicated solution and aqueous solution of polyvalent metal salts. Fringe of polymer-silicate solution is injected in form of mixture of 0.05-0.1% solution of camcel with 5-10% solution of sodium silicated taken in ratio of 1:1. Fringe of aqueous solution of polyvalent metal salt is injected in form of aqueous solution of calcium chloride with density of 1.05-1.1 g/cu. cm. Fringes of solutions are injected in same volumes, 5-200 cu. cm each, until well injectivity drops by not in excess of 50%, with additional forcing of at least 40% of solution fringe volume. EFFECT: higher efficiency of isolation of high-permeability formation intervals due to increase of strength characteristics of grouting body, reduced its synergism in time, increased duration of isolation effect. 2 tbl, 2 ex

Description

 The invention relates to the oil industry, in particular to methods for isolating highly permeable formation intervals in injection and production wells.

 A known method of isolating highly permeable intervals of the formation, including the sequential injection of a solution of sodium silicate and mineralized water containing salts of divalent alkaline-earth metals (eg, calcium chloride) separated by a buffer rim of fresh water [1].

 The disadvantage of this method is the low duration of the insulation effect due to the low plugging properties of the sediment formed in the formation.

 Closest to the invention in technical essence is a method of isolating highly permeable intervals of the formation, including the sequential injection in fresh water buffers of the rims of a polymersilicate solution of a salt of a polyvalent metal [2].

 The disadvantages of the known technical solutions are the relatively low strength characteristics of the plugging mass and the presence of syneresis, i.e. the volume of sludge formed decreases over time, which leads to a decrease in the duration of the insulation effect and a breakthrough of water to the faces of production wells.

 The invention solves the problem of increasing the efficiency of isolation of highly permeable intervals of the reservoir by increasing the strength characteristics of the plugging mass, reducing its syneresis in time and increasing the duration of the insulation effect.

The problem is solved in that in the method for isolating highly permeable intervals of the formation, which includes sequential injection of polymeric silicate solution rims and an aqueous solution of a polyvalent metal salt in fresh water buffers, the polymer solution silicate rim is injected in the form of a mixture of a 0.05-0.1% stone solution with 5 -10% sodium silicate solution, taken in the ratio 1: 1, and the rim of the aqueous solution of polyvalent metal salts is pumped in the form of an aqueous solution of calcium chloride with a density of 1.05-1.1 g / cm ³ , while the injection of the rims of the solution The ditch is carried out in equal volumes, 5-200 m ³ each, until the well injectivity is reduced by no more than 50%, with additional sales in the amount of not less than 40% of the volume of the rim of the solutions.

The essential features of the invention are:
- injection rims of polymer silicate solution;
- injection rims of an aqueous solution of a salt of a polyvalent metal;
- sequential injection in fresh water buffers of the rims of the above solutions;
- injection of the edges of the polymer-silicate solution in the form of a mixture of a 0.05-0.1% solution of camphor with a 5-10% solution of sodium silicate, taken in a ratio of 1: 1;
- injection rims of an aqueous solution of a salt of a polyvalent metal in the form of an aqueous solution of calcium chloride with a density of 1.05-1.1 g / cm ³ ;
- the injection of the rims of the solutions is carried out in equal volumes, 5-200 m ³ each, to reduce the injectivity of the well by no more than 50%;
- injection of rims of solutions with additional sales in the amount of not less than 40% of the volume of the rims of the solution.

 Signs 1-3 are common with the prototype, signs 4-8 are the salient features of the invention.

 The sequential injection of the rims of the camcelsilicate mixture and the aqueous solution of calcium chloride is carried out in alternating portions in order to increase the number of mixing zones and, accordingly, the volume of the plugging mass resulting from the interaction of the camcelsilicate mixture and the aqueous solution of calcium chloride.

 The volumes of the edges of the reagents in fresh water buffers, as well as the total volume of injected solutions are selected based on the specific geological characteristics of the well, the current state of development of the reservoir area and the required treatment radius.

 When developing oil deposits with heterogeneous reservoirs by flooding, premature breakthrough of injected water occurs at highly permeable intervals in oil producing wells. This leads to a decrease in the efficiency of oil displacement by water and to a decrease in oil recovery. To combat water breakthrough at high permeability intervals of the reservoir, work is carried out to isolate these intervals in injection and production wells. However, the effect of the work is short, which leads to a breakthrough of water to the bottom of production wells and a decrease in the current oil recovery.

 It is known from field practice that when the injection well injectivity is reduced by more than 50% during processing, there is a noticeable decrease in the rate of fluid withdrawal from the surrounding producing wells. In this regard, there may be cases when the loss in oil production due to a decrease in liquid withdrawal is not compensated by additional oil obtained as a result of a decrease in water cut at the facility, i.e. an increase in oil recovery is accompanied by a decrease in current oil production. As a result of this, the injection rate of the well should not be reduced by more than 50% during processing. It is also known from field practice that when processing a producing well, after pumping a water-insulating material into the formation, it is necessary to sell it. The sales volume should be no less than 40% of the volume of the downloaded composition, because in the producing well, insulating material may fall into low-permeable oil-saturated intervals and it is necessary to restore the hydrodynamic connection with the formation, and in the injection well, pushing the insulating material deeper into the formation increases its coverage over the area.

 Kametsel is a water-soluble polymer, produced by the domestic industry in accordance with TU 2231-001-35193780-96.

 To obtain comparative data on known and new technical solutions, a complex of laboratory studies was carried out.

 In the first series of experiments, the interaction of the sodium silicate + camcel and sodium silicate + polyacrylamide systems with a solution of calcium chloride was studied. The experiments were carried out according to the following program: first, mixtures of sodium silicate with camels were prepared in a ratio of 1: 1 (as a prototype a mixture of sodium silicate with polyacrylamide was prepared in the same ratio), then the prepared mixtures were placed in a measuring cylinder and a solution of calcium chloride also in a ratio of 1: 1. During the experiment, the sediment volume and the static shear stress were determined, which characterize the plugging properties of the system. The measurements were carried out one day after mixing (after the syneresis of the system). The results of the experiments are presented in table. 1.

 As can be seen from the table. 1, precipitates formed during the interaction of the sodium silicate + camcel system with a solution of calcium chloride, ceteris paribus, have higher strength properties than precipitates formed during the interaction of silicate polyacrylamide mixtures with a solution of calcium chloride. The strength and volume of the precipitate decrease with decreasing concentration in the composition of sodium silicate and stone, as well as the density of the solution of calcium chloride. A decrease in the concentration of reagents in the composition below the stated leads to a deterioration in the properties of the plugging precipitate, and an increase does not cause a significant improvement in the characteristics of the precipitate.

In the second series of experiments, an increase in the efficiency of isolation of highly permeable intervals of the formation by the proposed method in comparison with the prototype was evaluated. The experiments were carried out on a physical model of the formation with a length of 60 cm and a diameter of 3 cm. The model of the porous medium was quartz sand with a fraction of 0.1 mm. Previously, the reservoir model under vacuum was saturated with fresh water and its permeability was determined. In the first experiment of this series, 25 cm ^{3 of a} mixture containing 12.5 cm ^{3 of a} 0.1% solution of stone and 12.5 cm ^{3 of a} 10% solution of sodium silicate, 5 cm ^{3 of} fresh water and 25 were successively pumped into the reservoir model cm ^{3 a} solution of calcium chloride with a density of 1.1 g / cm ³ and then switched to the injection of fresh water. In the second experiment, 25 cm ^{3 of a} polymer silicate mixture (12.5 cm ^{3 of a} 0.1% PAA solution and 12.5 cm ^{3 of a} 10% sodium silicate solution), 5 cm ^{3 of} fresh water and 25 cm were successively pumped into the reservoir model ³ solution of calcium chloride with a density of 1.1 g / cm ³ and then switched to the injection of fresh water. In the course of the experiments, the permeability dynamics of the reservoir model was monitored. The results of the experiments are presented in table. 2.

 As can be seen from the table. 2, the proposed method improves the insulation efficiency of highly permeable intervals of the reservoir in comparison with the prototype.

 Examples of specific performance.

Example 1. By flooding, an oil reservoir is developed with the following characteristics: effective formation thickness - 10 m, porosity - 0.18, absolute permeability - 0.80 μm, reservoir temperature - 78 ^o C, the ratio of permeability of high permeability and low permeability intervals is 2.5 . In a highly permeable interval, the injected water broke through into the production well, the water cut of the product reached 95%.

400 m ^{3 of a} camcelsilicate mixture (200 m ^{3 of a} 0.1% solution of stone and 200 m ^{3 of a} 10% solution of sodium silicate) and 400 m ^{3 of a} solution of calcium chloride with a density of 1.05 g / cm ^{3 are} pumped into the injection well. The injection is carried out by alternating rims of 80 m ³ each through fresh water buffers of 10 m ³ . In total, 5 injection cycles are carried out. The sales volume is 35 m ³ .

 Example 2. Develop an oil reservoir, as in example 1. The water content of the product reached 90%.

40 m ^{3 of the} camcelsilicate mixture (20 m ^{3 of a} 0.05% solution of stone and 20 m ^{3 of a} 5% solution of sodium silicate) and 40 m ^{3 of a} solution of calcium chloride with a density of 1.1 g / cm ^{3 are} pumped into the production well. The injection is carried out by alternating rims of 10 m ³ each through fresh water buffers of 1 m ³ . In total, 4 injection cycles are carried out. The sales volume is 20 m ³ .

 Example 3. Develop an oil reservoir, as in example 1. Water cut production reached 98%.

The injection is carried out both in the injection and in the producing well at the same time. At the same time, 400 m ^{3 of the} camcelsilicate mixture (200 m ^{3 of a} 0.05% solution of stone and 200 m ^{3 of a} 5% solution of sodium silicate) and 400 m ^{3 of a} solution of calcium chloride with a density of 1.05 g / cm ^{3 are} pumped into the injection well . The injection is carried out by alternating rims of 80 m ³ each through fresh water buffers of 10 m ³ . In total, 5 injection cycles are carried out. The sales volume is 40 m ³ . 60 m ^{3 of the} camcelsilicate mixture (30 m ^{3 of a} 0.1% solution of stone and 30 m ^{3 of a} 10% solution of sodium silicate) and 60 m ^{3 of a} solution of calcium chloride with a density of 1.1 g / cm ^{3 are} pumped into the production well. The injection is carried out in alternating rims of 12 m ³ each through fresh water buffers of 1.5 m ³ . In total, 5 injection cycles are carried out. The sales volume is 25 m ³ .

 The application of the proposed method for the isolation of highly permeable intervals of the reservoir improves the efficiency of isolation by increasing the strength properties of the plugging deposit and the duration of the effect and, as a result, increase the oil recovery coefficient of the oil reservoir.

Sources of information
1. US patent 3658131, MKI E 21 In 33/138, E 21 In 43/32, 1970.

 2. Patent VNR 186866, MKI E 21 43/12, 1982 (prototype).

Claims (1)

A method of isolating highly permeable formation intervals, comprising sequentially injecting polymeric silicate rims and an aqueous solution of a polyvalent metal salt in fresh water buffers, characterized in that the polymeric silicate rim is pumped in the form of a mixture of a 0.05-0.1% stone solution from 5-10 % solution of sodium silicate in the ratio 1: 1, and the rim of an aqueous polyvalent metal salt solution is injected in the form of an aqueous solution of calcium chloride density 1.05-1.1 g / cm ^3, wherein the rims injection solutions wasps implemented at equal volumes, 5-200 m ³ each, to reduce the injectivity of the well is not more than 50%, with an additional prodavkoy in amounts not below 40% by volume solution rim.

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