SU1483041A1 - Arrangement for isolating formations in borehole - Google Patents

Abstract

The invention relates to the mining industry and is intended to increase the tightness of the cement ring (CK) during well cementing. The purpose of the invention is to improve the reliability of separation of layers due to the possibility of damping loads in the casing string (C) and reducing the possibility of the formation of an overflow between the OK and the cement stone. For this purpose, the casing 2 is rigidly connected with the body 1 and forming a hermetic annular cavity (CS) 3 with it. The casing 2 is made of an elastic material. At the same time, KP 3 is filled with a compressible working agent under pressure, which prevents the casing 2 from seeing the weight of the column of cement slurry over OK. At the moment of cementing, favorable conditions are formed in the space between the casing 2 and the borehole wall to obtain a uniform CC. The tight adhesion of the CK to the rock is achieved by removing the mudcake or washing away the plaque. After the cement sets, the axial and radical deformations of the OK, caused by changing conditions, are not transmitted by the CK due to the presence of KP 3, filled with a working agent, and does not cause a leakage of the CK. 1 il.

Description

The invention relates to the mining industry, in particular, to devices designed to increase the tightness of a cement ring during well cementing.

The aim of the invention is to improve the reliability of the separation of the layers due to the possibility of damping loads in the casing and reducing the possibility of the formation of a flow between the casing and the cement stone.

The drawing shows a device for the separation of the layers.

The device comprises a housing 1 with an axial channel and a housing 2 rigidly connected with the housing 1 and forming with it an annular cavity 3 filled with a working agent.

The casing 2 is made of an elastic material and has a resin-sanding coating 4. On the housing 1 above and below the casing 2, centering lights are installed with a scraper 5 and a sealing ring 6. The annular cavity 3 is sealed and filled with compressible working agent (air) under pressure to prevent crushing casing 2

 from the mass of the column of cement slurry behind the column, for which case 2 is equipped with an inlet valve (not shown).

The device works as follows.

Before running the casing, the installation intervals of the covers 2 against resistant impermeable or permeable interlayers are selected, and the casing is equipped with this device. Depending on the expected changes in the internal pressure in the casing, temperature and well designation, calculate the wall thickness of the casing 2 for each interval, the size of the annular cavity 3, which should be greater than the radial deformation of the pipe, and choose a system for fixing the casing on the case or pinching both ends , or sliding on sealing rings. From the bottom and on top of the casing they install lights with scrapers 5, acting while strutting

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are using all known measures that increase the degree of replacement of the washing liquid with cement mortar while simultaneously diverting the column.

At the time of cementing, favorable conditions are formed in the space between the casing 2 and the borehole wall to obtain a uniform cement ring, the tight adhesion of which with the rock is achieved by removing the mudcake if the formation is permeable, or by scaling away if the formation is impenetrable. Better adhesion of the cement to the metal of the casing 2 can be achieved by a composition that enhances the adhesion of the metal to the cement (for example, a tar-sanding coating) deposited on the outer surface of the casing.

After the cement sets, the axial and radial deformations of the casing, caused by changing conditions, are not transferred to the cement ring due to the presence of an annular cavity 3 filled with a working agent (air); and do not cause leakage of the cement ring.

The device may be positioned against the wellbore intervals with their preliminary expansion or treated with solutions forming hardening crusts.

For ultra-deep wells, pressurized air is pumped into the annular cavity.

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Claims (1)

Invention Formula A device for separating formations in a well, comprising a housing with an axial channel and a housing rigidly connected to the housing and forming an annular cavity with it, filled with a working agent, characterized in that, in order to increase the reliability of separation of the formations due to the possibility of damping loads in the casing string and reduce the possibility of the flow between the casing and the cement stone, the casing is made of an elastic material / annular cavity - sealed, filled with compressible working agent under