RU2354804C1 - Method for well repair - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to oil industry and may find application in well repair. According to method, pipe string is lowered in well. Pipe string bottom is lowered to the depth that is 20-30 m below interval of detected violation of casing pipe. Minimum circulation of liquid is created through pipe string and well tube space. Liquid outlet from tube space is sent to ditch system. Back pressure of 3-4 MPa is established at wellhead by closure of valve at the outlet from tube space. Cement mortar is pumped through casing string with its discharge from casing string bottom to interval of violation. Casing string is lifted, and its bottom is installed by 20-40 m higher than interval of violation, gate valve is closed at the outlet from well annular space, and cement grout is pushed into interval of violation in design volume. Pipes shoe is lifted to the height where it is planned to install head of cement bridge, and excess cement mortar is removed by return circulation of liquid in annular space and pipe string. Pipe string is lifted or completely withdrawn. Technological exposure is performed for cement hardening. Depth of cement sleeve location is identified. Casing string is pressurised. Cement sleeve is drilled down to interval by 5-10 m below interval of violation. Repeated pressurisation of casing string is carried out. In case of string tightness, cement sleeve is completely drilled. In case of insufficient tightness of casing string, which as a rule occurs after quite considerable violations, repeated sealing of violation is carried out.

EFFECT: increased reliability of well casing pipe repair.

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Description

The invention relates to the oil industry and may find application in the repair of wells.

A known method of restoring the integrity of the production casing of the well, according to which a gelling composition is pumped into the zone of the interval of violation of the integrity of the production casing. A pipe string is lowered into the well with a layout installed at its lower end. Place the specified layout below the violation interval. Use the layout represented by a conical shoe made in the form of a frame of soft metal filled with a mixture of cement and crumbs of soft metal. Disconnect the cone shoe and push it to the bottom. Fill the perforation interval with sand. The deflated pipe string is sealed relative to the production string by pouring cement. A deflated pipe string is suspended. After drilling a cement cup, sand is removed from the well and put into operation (RF Patent No. 2142112, published. 1998.12.27).

The known method does not exclude the inclusion of a gelling composition in the perforation interval.

Closest to the proposed invention in technical essence is a method of repairing a well, which includes locating a repair site, setting up an explosive packer, releasing a flexible sleeveless long pipe of a coiled tubing installation, injecting cement mortar through it, pumping cement mortar, lifting a flexible sleeveless long pipe of a coiled tubing installation from a well, conducting technological exposure, drilling a cement bridge to an explosive packer, determining well tightness, drilling an explosive packer (Pat ent of the Russian Federation No. 2280754, published. 2006.07.27 - prototype).

The method is complex and does not provide sufficiently reliable repair of the casing of the well.

In the proposed invention solves the problem of improving the reliability of the repair of the casing of the well.

The problem is solved in that in a method of repairing a well, including lowering a pipe string into the well, pumping and selling cement slurry, raising the pipe string, holding the process, drilling the cement bridge and determining the tightness of the well, according to the invention, the bottom of the pipe string is lowered to a depth of 20- 30 m below the interval of the detected casing string disturbance, create a minimum fluid circulation through the pipe string and the annulus of the well, the fluid exit from the annulus is directed to the the system, establish a backpressure at the wellhead 3-4 MPa by covering the valve at the exit from the annulus, inject cement with the outlet from the bottom of the pipe string to the violation interval, raise the column and set the bottom of the pipe string 20-40 m above the violation interval close the valve at the exit of the annular space of the well, push cement mortar into the violation interval, raise the shoe of the pipe to a height where it is planned to install the head of the cement bridge, and produce removal of excess cement mortar by reverse circulation of fluid, raise the pipe string to a safe distance or remove it completely, carry out technological exposure to harden the cement, determine the depth of the cement cup, compact the casing, drill the cement cup to an interval 5-10 m below the disturbance interval, produce repeated pressure testing of the casing string; when the casing is tight, drill the cement cup completely; when the casing is leaking, plague repeated sealing violations.

After plugging the violation, removing excess cement mortar and raising the tubing string, technological exposure is carried out to harden the cement, the depth of the cement glass is determined, the casing is pressed, the cement glass is drilled to an interval of 5-10 m below the violation interval, and the casing is re-pressed columns, when the columns are tight, drill the cement cup completely, when the casing is leaking, re-seal nation violation.

SUMMARY OF THE INVENTION

Existing methods for sealing violations of casing strings provide for the installation of an intermediate bridge to install an intermediate bridge 20-30 m below the violation. At the same time, time and materials are lost on the installation of the bridge, and the quality of the repair leaves much to be desired. When setting the intermediate bridge due to partial leakage in violation of the casing of cement and its setting, the acceleration of the violation decreases, the insulating cement penetrates the violation only partially and to a shallow depth. With an apparently high-quality repair, the reliability of isolation of the violation is low. The proposed method solves the problem of improving the reliability of repair of the casing of the well. The problem is solved as follows.

Sealing violations of the casing strings is carried out without installing an intermediate bridge under the violation. To do this, perform the following operations.

A string of pipes, for example tubing, is lowered into the well. The bottom of the pipe string is lowered to a depth of 20-30 m below the interval of the detected casing string disturbance. Create a minimum (of the order of 6-12 l / sec) circulation of fluid (water) through the pipe string and the annular space of the well (the space between the pipe string and casing) at low speed operation of the cementing unit. The fluid exit from the annulus is sent to the groove system. Set back pressure at the wellhead 3-4 MPa by covering the valve at the exit of the annulus. If the wellbore is filled with sewage or produced water, a buffer fluid — fresh water — is injected in the amount of about 0.15-0.25 m ³ . Cement mortar is injected along the pipe string with its output from the bottom of the pipe string to the violation interval.

If the specific injectivity of the violation is more than 1.0-1.5 m ³ / h · MPa, the valve at the exit from the annular space of the well is closed and grouting mortar is pressed in violation of the tightness of the well. After grouting, the pipe shoe is raised to a height where the head of the cement bridge is planned to be installed, excess cement mortar is removed by reverse circulation of liquid, the pipe string is lifted to a safe distance or completely removed.

If the specific injectivity is less than 1.0-1.5 m ³ / h · MPa, raise the pipe string and set the bottom of the pipe string 20-40 m above the violation interval. The valve is closed at the exit from the annular space of the well and cement cement is forced into the interval of violation in the calculated volume. The excess cement mortar is removed by reverse circulation of fluid through the annulus and the pipe string. Raise the pipe string to a safe distance of the order of 300-400 m above the violation or completely remove the pipe string.

After plugging the violation, removing excess cement mortar and raising the tubing string, technological exposure is carried out to harden the cement. Determine the depth of the cement glass lapping pipe string or geophysical method. Compress the casing at the permissible pressure for a given well. Drill a cement glass to an interval of 5-10 m below the violation interval. Re-pressure the casing. When the columns are tight, the cement cup is fully drilled. With insufficient tightness of the casing, which occurs, as a rule, with very significant violations, re-sealing the violation.

As a result, it is possible to completely isolate the violation of the casing string and extend the life of the well.

Concrete example

They repair well No. 5555. The diameter of the production casing is 146 mm, the perforation interval is 1669.8-1682.2 m, the depth of the cut-off bridge is 1571 m.

The well is filled with reservoir technical fluid with a density of 1.18 g / cm ³ . The disturbance interval is 815-820 m, the injectivity of the violation is 247 m ³ / day at a pressure of 7 MPa, the specific injectivity is 1.4 m ³ / h · MPa.

A tubing string with a diameter of 73 mm and a funnel pen at the end is lowered into the well. The bottom of the pipe string is lowered to a depth of 840 m (20-25 m below the interval of the detected casing string disturbance). Minimum circulation of water through the pipe string and the annular space of the well is created by the operation of the cementing unit at a speed of 8-10 l / s. The fluid exit from the annulus is sent to the groove system. Install a back pressure at the wellhead of 3.5 MPa by covering the valve at the exit of the annulus. Injected into the tubing string 0.2 m ³ buffer fluid (fresh water). Cement mortar is injected through a pipe string with its output from the bottom of the pipe string to a violation interval of 2.8 m ³ . Close the valve at the exit of the annular space of the well and push cement into the interval of violation in the amount of 3.29 m ^{3 of} cement + 0.2 m ^{3 of} buffer fluid from fresh water + 1.77 m ^{3 of} squeeze fluid with a density of 1.18 g / cm ³ . The pressure at the mouth increased from 1.5 to 8.5 MPa. The residual pressure is 6.5 MPa. Lift the tubing shoe to a depth of 785 m (planned head of the cement bridge). The excess cement mortar is removed by reverse circulation of water through the annulus and the pipe string in a volume of 4 m ³ . Raise the pipe string 315 m above the breach. Carry out technological exposure to the hardening of cement within 24 hours. The depth of finding the cement cup by lapping the pipe string, which is at a depth of 783.3 m, is determined. The casing is tested at an allowable pressure for a given well equal to 9.0 MPa. Drill a cement glass to an interval of 822 m (7 m below the violation interval). Re-pressure the casing under the same pressure. The column is tight.

Analysis of a series of repairs according to the proposed method shows that the success of repairs, their reliability is close to 100%, while the prototype reliability of repairs does not exceed 85%.

The application of the proposed method will improve the reliability of the repair of the casing of the well.

Claims (1)

A method of repairing a well, including lowering a pipe string into a well, injecting and selling cement slurry, raising a pipe string, holding a technological shutter, drilling a cement bridge and determining the tightness of the well, characterized in that the bottom of the pipe string is lowered to a depth of 20-30 m below the interval detected violations of the casing string, create a minimum fluid circulation through the pipe string and the annulus of the well, the fluid exit from the annulus is sent to the groove system, set back pressure at the wellhead 3-4 MPa by covering the gate valve at the exit from the annulus, inject cement from the bottom of the pipe string to the violation interval, raise the column and set the bottom of the pipe string 20-40 m above the violation interval, close the valve by leaving the annulus of the well, cement cement is forced into the violation interval, the shoe of the pipes is raised to the height where it is planned to install the head of the cement bridge, and the excess cement is removed of the solution by reverse circulation of the liquid, raise the pipe string to a safe distance or completely remove it, carry out technological exposure to harden the cement, determine the depth of the cement cup, test the casing, drill the cement cup to an interval of 5-10 m below the breakdown interval, re-pressurize the casing string, with the tightness of the casing, drill the cement cup completely, with the casing leaky, re-seal tion violation.