RU2234590C1 - Method for isolating well against water influx - Google Patents

Abstract

FIELD: oil industry, particularly for well isolation.

SUBSTANCE: method involves filling well hole annulus with water, filling remainder space with liquid hydrocarbon; pumping aqueous solution of polyacrylamide with hardening agent; feeding aqueous clay dispersion and after that repeatedly pumping aqueous solution of polyacrylamide with hardening agent; driving above solutions by oil; maintaining ratio between initial pumping pressure at well head and final pumping pressure within range of 1:(1.5 - 2.2); curing thereof for hardening polyacrylamide; operating well; repeating above operations if ratio between initial pumping pressure to final pumping pressure is out of above range up to obtaining this predetermined ratio.

EFFECT: increased efficiency of well installation.

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Description

The invention relates to the oil industry and may find application in isolating water inflows into a well.

A known method of isolating the influx of water into a well, including the injection of a solution of polyacrylamide and clay slurry [USSR Author's Certificate No. 933963, class. E 21 B 43/32, publ. 1983].

The disadvantages of this method is the rapid precipitation of clay near the well and the rapid increase in injection pressure.

Closest to the invention, the technical essence is a method for treating a bottom-hole zone of a well, comprising sequentially pumping through an injection well an aqueous solution of polyacrylamide and an aqueous clay dispersion (polymer dispersed system), with rims in a volume of 50-200 m ³ each, to reduce the injectivity of the well by no more than 50% [RF Patent No. 2044872, cl. E 21 B 43/22, publ. 1995].

The known method does not allow sufficiently effectively isolate water inflows into the well, the isolation is short-lived, during operation isolation of the insulating material into the well takes place and the water cut of the produced oil increases.

The invention solves the problem of increasing the efficiency of isolation of water inflows into the well.

The problem is solved in that in a method for isolating water inflows into a well, comprising sequentially injecting an aqueous solution of polyacrylamide and an aqueous dispersion of clay through the well, according to the invention, the aqueous solution of polyacrylamide is used with a hardener, the annulus of the well is pre-filled with water, the remaining space of the well is filled with hydrocarbon liquid, after injection water dispersion of clay is injected with an aqueous solution of polyacrylamide with a hardener, squeezed with oil in the volume of the well and spend restraint technologically for curing polyacrylamide, wherein the ratio of the initial injection pressure to the final pressure at the wellhead injection wells is maintained as 1: (1,5-2,2). If the ratio of the initial injection pressure to the final injection pressure at the wellhead is not equal to 1: (1.5-2.2), repeat the operation until the specified ratio is reached.

The features of the invention are:

1) the use of an aqueous solution of polyacrylamide with a hardener;

2) filling the annulus of the well with water;

3) filling the remaining space of the well with hydrocarbon fluid;

4) injection through the well of an aqueous solution of polyacrylamide;

5) injection through the well of an aqueous dispersion of clay;

6) re-injection through the well of an aqueous solution of polyacrylamide;

7) the sale of oil in the volume of the well;

8) holding technological exposure for curing polyacrylamide;

9) the ratio of the initial injection pressure to the final injection pressure at the wellhead as 1: (1.5-2.2).

10) if the ratio of the initial injection pressure to the final injection pressure at the wellhead is not equal to 1: (1.5-2.2), repeat the operations until the specified ratio is reached.

Signs 4, 5 are similar to the prototype, signs 1-3, 6-9 are the salient features of the invention, sign 10 is a particular feature of the invention.

SUMMARY OF THE INVENTION

During the development of an oil deposit, individual interlayers are flooded, water inflows into the oil producing well occur. Isolation of water inflows allows to reduce the water cut of the extracted oil. Existing methods do not always lead to reliable and durable isolation of water inflows. The proposed invention solves the problem of increasing the durability of the isolation of water inflows into the well.

In the proposed method for isolating water inflows, the annular space of the well is filled with water, and the remaining space of the well is filled with hydrocarbon liquid, for example, oil. Such filling in the absence of air in the annulus contributes to a better forcing of the solutions into the bottomhole zone of the well. With the subsequent flow of hydrocarbon fluid into the near-well zone of the well, pore hydrophobization occurs, which allows most of the fresh-water composition injected afterwards not to settle near the well, but to penetrate deep into the flooded zone, providing deep isolation.

Then, an aqueous solution of polyacrylamide with a hardener is pumped through the well. Notice the injection pressure as initial. As a hardener, chromium salts are used, for example, chromium acetate with a ratio of polyacrylamide: chromium acetate as 10: (0.9-1.1), respectively. As an aqueous solution of polyacrylamide using a solution obtained by dissolving 1-3 kg of polyacrylamide in 1 m ³ fresh water. The injection volume of an aqueous solution of polyacrylamide with a hardener is 30-35 m ³ .

After that, an aqueous dispersion of clay is pumped through the well in a volume of 20-25 m ³ . As an aqueous clay dispersion, a dispersion obtained by mixing 300-600 kg of clay in 1 m ^{3 of} water is used.

Following this, re-injection through the well of an aqueous solution of polyacrylamide with a hardener is carried out in a volume of 15-25 m ³ . Solutions push oil through the well. Notice the injection pressure as final. If the ratio of the initial injection pressure to the final injection pressure at the wellhead is not equal to 1: (1.5-2.2), the operations are repeated, possibly with reduced volumes of an aqueous solution of polyacrylamide and an aqueous dispersion of clay to half of those used in the first stage. After reaching a certain ratio of the initial injection pressure to the final injection pressure, technological exposure is carried out to cure the polyacrylamide for approximately 2.5-4 days.

Curable polyacrylamide creates a strong gel under formation conditions that is practically incapable of movement. Clay in the reservoir, located between the two rims of the cured polyacrylamide, reliably tampons the flooded area. Their combined use allows you to create durable insulation of water inflows into the well. The method is especially effective in isolating water inflows into a horizontal well.

An example of a specific implementation of the method

Isolate water inflows in a horizontal well with a horizontal well 100 m long in a terrigenous reservoir. They fill the annulus of the well with water, and the rest of the well with dehydrated, degassed oil of the same reservoir. At an initial pressure of 5 MPa at the mouth, an aqueous solution of polyacrylamide with a hardener is pumped through the well. As a hardener, chromium acetate is used with a ratio of polyacrylamide: chromium acetate as 10: 1, respectively. As an aqueous solution of polyacrylamide, a solution obtained by dissolving 2 kg of polyacrylamide in 1 m ^{3 of} fresh water is used. The injection volume of an aqueous solution of polyacrylamide with a hardener is 33 m ³ .

After that, an aqueous dispersion of clay in the volume of 23 m ^{3 is} pumped through the well. As an aqueous clay dispersion, a dispersion obtained by mixing 450 kg of clay in 1 m ^{3 of} water is used.

Following this, re-injection through the well of an aqueous solution of polyacrylamide with a hardener in a volume of 20 m ^{3 is} carried out. The solutions are pressed with oil in the well volume at a final pressure of 10 MPa. It is determined that the ratio of the initial injection pressure to the final injection pressure at the wellhead, equal to 1: (1.5-2.2), is achieved. Spend technological exposure to cure polyacrylamide for 3 days. and launch the well into operation.

As a result of the work performed, the water cut of the extracted products decreased from 85 to 35%. Well research showed that this insulation retained its function after 1.5 years of operation.

The application of the proposed method will improve the durability of the isolation of water inflows into the well.

Claims (2)

1. A method of isolating water inflows into a well, including the sequential injection of an aqueous solution of polyacrylamide and an aqueous dispersion of clay through the well, characterized in that the aqueous solution of polyacrylamide is used with a hardener, the annulus of the well is pre-filled with water, the remaining space of the well is filled with hydrocarbon liquid, after the aqueous dispersion is injected clay injected an aqueous solution of polyacrylamide with a hardener, squeezed with oil in the volume of the well and hold technological exposure for I cure polyacrylamide, while the ratio of the initial injection pressure to the final injection pressure at the wellhead is maintained as 1: (1.5-2.2). 2. The method according to claim 1, characterized in that if the ratio of the initial injection pressure to the final injection pressure at the wellhead is not equal to 1: (1.5-2.2), the operations are repeated until the specified ratio is reached.