RU2296209C1 - Method for isolation of formation water inflow in well - Google Patents

Abstract

FIELD: oil industry, particularly methods or devices for cementing, for plugging holes, crevices, or the like.

SUBSTANCE: method involves performing injection of flowable cement mortar through flexible flush-joint pipe of coiled tubing assembly into hole annuity; performing time-delay to provide cement hardening. The flexible flush-joint pipe is made as pipe having diameter of not more than 32 mm. Pipe with lesser diameter is lowered into hole annuity from ground surface between surface casing and production string. Cement mortar has density and pressure experimentally selected in dependence of length of pipe to be lowered. Cement mortar fills pipe interior and hole annuity up to day surface level. During cement hardening pipe is left in hole annuity. After cement hardening the pipe is cut at day surface level.

EFFECT: increased simplicity due to elimination of cement bridge forming in well.

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Description

The invention relates to the oil industry and can find application in isolating the influx of formation water into the well, in particular in isolating places of violations of production casing in the area of the conductor.

A known method of processing the bottom hole zone of a well equipped with a tubing string and a packer under conditions of abnormally low reservoir pressure, including determining the interval of insulation work, installing an insulation bridge, waiting for cement to harden, and putting the well into operation. After determining the interval of insulation work, the tubing string is perforated with special holes above the roof of the insulation bridge, flexible couplingless long pipes of the coiled tubing unit are lowered into the well without preliminary killing, and a viscous fluid is pumped into the bottomhole when the well is closed, the volume of the waterproofing solution is determined by the volume of viscous fluid when she reaches the special holes, they purge the well until the viscous fluid is completely removed, and then pump it with a waterproofing creates carried installation insulating bridge at spetsotversty, raised from the well flexible tubes, waiting is carried hardening grout in the borehole and run job (Application for RF invention № 2001133624/03, publ. 2003.08.20).

The known method allows you to install a cement bridge in the well. However, with a high location of water manifestations, the application of this method will lead to almost complete filling of the well with cement and, in fact, to well liquidation.

Closest to the invention in technical essence is a method of isolating the influx of formation water into the well, comprising injecting the grouting mortar under pressure into the water-developing part of the reservoir and holding the well for the duration of the grout setting. A flexible pipe is lowered into the pipe space of a well under pressure by means of a coiled tubing unit, valves are opened on the pipe and annular spaces, the wellbore is filled with gas condensate through it, and cement slurry is prepared in the preparation block by mixing cement with a setting retarder and a reagent, increasing the fluidity of the solution, in the amount necessary to eliminate the influx of formation water, determined by calculation by known methods, depending on the geologist According to the results of geophysical and gas-dynamic studies of the well, the reservoir’s parameters are pumped through a flexible pipe with a buffer fluid, for example methanol, in a volume of 0.3-0.6 of the volume of a flexible pipe, the annulus is closed and cement slurry is pumped through a flexible pipe to fill the wellbore wells in the interval of the water-developing part of the reservoir, the number of wells, after raising the cement slurry in the well to a predetermined height, close the pipe space and begin to push the cement slurry located in a flexible pipe, into the water-developing part of the formation, sequentially injected with a buffer liquid and a squeezing solution, for example, by first injecting methanol in a volume of 1.0-1.3 volumes of a flexible pipe, and then gas condensate, in the required volume, but not more than the internal volume of a flexible pipes, until the cement slurry is pumped through the flexible pipe in the volume of 0.3-0.5 volumes of the flexible pipe, then the pipe and annular spaces of the well are opened and, simultaneously with the injection into the flexible pipe, gas condensate is pumped into the pipe and annular space to prevent the rise of grouting mortar in the pipe and annular space above the interval of the water-developing part of the formation, then the shoe of the flexible pipe is raised 1 m above the interval of the water-developing part of the formation, the excess cement slurry is cut and washed with gas condensate supplied through the flexible pipe into the pipe the space and leaving them there in a liquid state, after waiting for the cement to harden, lower the flexible pipe to the head of the cement cup and test it for strength, applying the injector of a coiled tubing unit through a flexible pipe with a force of 4.0-5.0 kN, then hydraulic testing of the cement bridge is carried out, after which the flexible pipe is removed from the well (Application for invention of the Russian Federation No. 2003117291, publ. 2005.01.10 - prototype).

The known method allows you to isolate the water-developing part of the reservoir, however, in this case, a cement bridge is formed in the well, separating the well into upper and lower parts. To restore the well’s working capacity, inevitably, it is necessary to carry out work to remove the cement bridge from the well.

The proposed invention solves the problem of simplifying the method by eliminating the formation of a cement bridge in the well.

The problem is solved in that in the method of isolating the influx of formation water into the well, including pumping a coiled tubing installation into the annular space of a fluid cement slurry through a flexible sleeveless pipe and holding it to wait for cement to harden, according to the invention, a small diameter pipe is used as a flexible couplingless long pipe small diameter is lowered into the annulus of the well from the surface between the conductor and the production string, the density of the cement and pressure p rockers are selected depending on the length of the pipe being lowered, the inner cavity of the small diameter pipe and the annulus to the day surface are filled with cement mortar, the cement is hardened when the small diameter pipe is in the annulus, and after the cement has hardened, the small diameter pipe is cut off at the level of the day surface.

The features of the invention are:

1) injection through a flexible sleeveless long pipe of a coiled tubing installation into the annular space of a fluid cement;

2) exposure to the expectation of hardening of cement;

3) the use of a pipe of small diameter as a flexible sleeveless long pipe;

4) the descent of a pipe of small diameter into the annulus of the well from the surface between the conductor and the production string;

5) the density of the cement mortar and the pumping pressure are selected depending on the length of the pipe being lowered;

6) filling with cement mortar the internal cavity of a pipe of small diameter and annular space to the day surface;

7) the expectation of cement hardening when the pipe is of small diameter in the annulus;

8) after cement hardening, shearing of a pipe of small diameter at the level of the day surface.

Signs 1 and 2 are common with the prototype, signs 3-8 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

When cementing a well, often cement slurry does not reach the top. At the same time, behind-the-casing flows, formation water inflows into the well through discontinuities of the production string are observed. Conventional methods can only partially resolve this problem. Existing methods, as a rule, have many adverse side effects associated with the formation in the well of cement bridges and similar formations. All this leads to the need to create a technology devoid of the above disadvantages. The proposed invention solves the problem of simplifying the method by eliminating the formation of a cement bridge in the well. The problem is solved as follows.

When isolating the influx of formation water into the well, they pump through a flexible sleeveless long pipe of a coiled tubing installation into the annular space of a fluid cement. As a flexible sleeveless long pipe, a small diameter pipe is used that can penetrate into the small gaps of the annulus, devoid of a cement ring. To do this, use a pipe with a diameter of up to 32 mm. A pipe of small diameter is lowered into the annulus of the well from the surface between the conductor and the production string. The density of the cement slurry and the pumping pressure are selected experimentally on the surface, depending on the length of the drain pipe of a certain small diameter.

Cement mortar fill the internal cavity of the pipe of small diameter and the annulus to the surface. Exposure to wait for the hardening of the cement. A pipe of small diameter is left in the annulus. Waiting for cement hardening is carried out when a small diameter pipe is in the annulus. After hardening of the cement, a small-diameter pipe is cut off at the level of the day surface.

With this technology, a cement bridge is not formed in the well. Since the cement mortar is poured into the annulus with the annulus open and without being crushed into the well through discontinuities in the production string, the cement does not enter the well at all and does not worsen the inner surface of the production string. Pumping pressure is required only for pushing cement mortar through a pipe of small diameter.

As a cement mortar, a cement mortar with a viscosity of up to 80 cPs is used. The pumping pressure is usually 6-10 MPa.

Concrete example

Repairing an oil well. In the annulus throughout the conductor there is no cement ring. An annulus is opened between the production string and the conductor. A flexible sleeveless long pipe with an outer diameter of 25.4 mm and a length of 20 m to the top of the cement ring is lowered into the annulus. The annulus is left open. To isolate the influx of formation water into the well, a cement mortar having a viscosity of 75 cPs is used. The pumping pressure is set to 8 MPa. Cement mortar fill the internal cavity of the pipe of small diameter and the annulus to the surface. Cut a pipe of small diameter at the level of the day surface. A pipe of small diameter is left in the annulus. Exposure is made to wait for cement to harden for 24 hours. Waiting for cement hardening is carried out when a small diameter pipe is in the annulus.

As a result, the flow of formation water into the well completely stopped. There is no cement bridge in the well and no traces of cement.

Application of the proposed method will simplify the isolation of the influx of formation water into the well.

Claims (1)

A method of isolating the influx of produced water into a well, including pumping a coiled tubing installation into the annular space of a fluid cement slurry through a flexible sleeveless long pipe and waiting for cement to harden, characterized in that a pipe with a diameter of up to 32 mm is used, which is lowered into the annulus of the well from the surface between the conductor and the production string, the density of the cement and the pumping pressure are selected experimentally in depending on the length of the flexible, collarless, long pipe being lowered, the inner cavity of the flexible, sleeveless pipe and the annulus to the day surface are filled with cement, waiting for the hardening of the cement is carried out while the flexible, collarless pipe is in the annulus, and after the cement has hardened, the flexible, collarless pipe is cut to the lengthy day surface.