RU2164588C1 - Process of operation of well - Google Patents

Abstract

FIELD: oil industry. SUBSTANCE: invention can find use in maintenance of production and injection oil wells. In agreement with process of operation of well new casing string of lesser diameter is sunk into well fitted with old casing string. Spaces are separated by pumping of anticorrosion fluid and bulk of cement mortar capable of disintegration in acid into space between old and new casing strings. Cement bridge is positioned above perforation interval and above lower part of new casing string. In case of replacement of new casing string new casing string is perforated at point of location of cement bridge and acidic solution is pumped till cement bridge disintegrates. EFFECT: prevention of any loss of liquid through casing string and improved maintainability of oil well.

Description

 The invention relates to the oil industry and may find application in the operation of production and injection wells.

A well-known method of operating a well, including lowering the production lift and auxiliary pipe, hydraulically disconnecting their cavities, filling with a medium with high thermal conductivity for heating or low thermal conductivity to reduce heat loss of the produced fluid and heating the medium (RF Patent N 2138622, class E 21 B 43 / 00, published. 1999)
The application of the known method allows to increase the productivity of wells in various methods of operation, to increase the overhaul period, to increase the reliability of downhole equipment. However, this does not exclude the loss of fluids through a worn casing, the conditions for well operation with increased pressures in conditions of increased maintainability are not created.

 The closest to the invention in technical essence is a method of operating a well, which includes running into a well equipped with an old casing string, a new smaller casing string, uncoupling the cavity of the well casing by pumping cement into the space between the old and new casing string, and operating the well (Operation experience repair and insulation work in production and injection wells, TNTO, Ser. "Production" M., VNIIOENG, p. 40-44).

 The disadvantage of this method is the lack of maintainability due to the indestructibility of the cement mortar.

 The invention solves the problem of ensuring maintainability of the well.

 The problem is solved in that in a method of operating a well, including descent into a well equipped with an old casing string, a new smaller casing string, uncoupling of the casing string of the well by pumping cement into the space between the old and new casing string, and operating the well according to the invention into the space anticorrosive fluid and a volume of cement mortar capable of degrading in acid are pumped between the old and new casing, and above the perforation interval and yshe bottom of the new casing in the space between the old and new column set cement bridge at the installation site which perforate the casing and the new acid solution pumped cement to fracture at the bridge to replace the new casing.

SUMMARY OF THE INVENTION
During well operation, the casing collapses due to corrosion and other influences. Over time, the casing loses its tightness and strength and ceases to fulfill its functions. In this case, pumping fluid or any flow of fluid in the column is accompanied by leaks into the near-wellbore space. To repair such a column is almost very difficult and ineffective. The invention solves the problem of ensuring maintainability of the well. The problem is solved by setting up a new casing string of smaller diameter in the well with cementing it with cement above the perforation interval and above (preferably 10-30 m) the bottom of the new casing string. The space over the resulting cement bridge is filled with an anti-corrosion liquid, which is used as dehydrated oil, distillate, an aqueous composition with aluminum powder and soda ash and others. At the same time, the entire well operation is carried out inside the new casing string. The well is used as production or injection. The use of cement mortar, forming a cement bridge, capable of breaking down in acid, determines the maintainability of the well. If necessary, the cement bridge can be destroyed by an acid solution. To do this, perform perforations at the site of the cement bridge, through which an acid solution is pumped. As cement mortars capable of forming a cement bridge that is degradable in acid, cement compositions with a filler easily destroyed in acid, such as chalk, limestone, etc. are used. The location of the cement bridge is above the perforation interval and preferably 10-30 m above the bottom of the new casing string allows maximum isolation of the old casing string from impacts during well operation and ensures reliable fastening of the new casing string in the well.

Concrete example
An oil producing well is operated at a depth of 1750 m. The perforation interval is located at a depth of 1700 m. The well is equipped with a 5 '' (five-inch) casing. After operating for 25 years, the casing of the well has corroded in many places, as a result of which there are massive fluid leaks. A new 3.5 '' (three and a half inch) casing is lowered into the well. The bottom of the new casing string is placed at a depth of 1680 m. The anticorrosive fluid and cement volume are pumped along the new casing string and the volume of cement mortar is filled until the space between the new and old casing string is filled with anticorrosive fluid and the volume of cement mortar is 25 m high 20 m higher bottom of a new casing string. Carry out technological exposure for the setting of cement mortar and the formation of a cement bridge. Dehydrated oil is used as an anticorrosive fluid, and a solution including cement and chalk in equal mass amounts is used as a cement mortar.

 A string of tubing with a deep pump is lowered into the well and oil is produced.

 When replacing a new casing string, a new casing string is perforated at the site of setting the cement bridge to its entire height of 25 m, pumping a 24% hydrochloric acid solution through the new casing string, and fluid is taken from the old casing string until the cement bridge collapses and the casing is released. After removing the new casing, the remains of the cement bridge are drilled.

 The application of the proposed method will ensure the maintainability of the well, reduce corrosion of the casing and prevent leakage of fluid into the near-wellbore space.

Claims (1)

 A method of operating a well, including a descent into a well equipped with an old casing string, a new casing string of a smaller diameter, uncoupling the cavities of the casing string and the well by injecting cement into the space between the old and new casing strings, and operating the well, characterized in that in the space between the old and a new casing is pumped with an anti-corrosive fluid and a volume of cement mortar that can degrade in acid, while above the perforation interval and above the bottom of the new casing th column in the space between the old and new columns set cement bridge at the installation site which perforate the casing and the new acid solution pumped cement to fracture at the bridge to replace the new casing.