SU1571218A1 - Method of isolating absorbing seams in boreholes - Google Patents

Abstract

The invention relates to the oil and gas industry. The goal is to increase the efficiency of the insulation process. In wells, absorbing formations are isolated by sequential injection of components of cement mixtures. The latter are placed in the absorption zone. Then, mixing and pumping into selectively isolated areas in the turbulent flow is performed by rotating the screw with a frequency of 0.5-10.0 s ^-1 and then moving it in the absorption zone from the bottom to the roof with predetermined device permutation intervals. The intensity of mixing of the components of the cement slurry, the flow rate and the injection pressure of the mixture into the absorbing channels are controlled by the frequency of rotation of the screw device, the limits of which depend on the combination of the dimensions of the well and the drill string. 1 il.

Description

The invention relates to the oil and gas industry, in particular to methods for isolating absorbing formations during drilling and well operation.

The purpose of the invention is to increase the efficiency of the process of isolating absorbing layers.

The drawing shows the implementation of the method.

The essence of the method consists in placing the components of the cement mixture in the absorption range, mixing them and pumping them into selectively selected areas, into permeable channels in the turbulent flow by rotating the auger with the frequency

0.5-10.0 and its subsequent displacement from the sole to the top of the absorption with the prescribed device permutation intervals.

The method is carried out as follows.

The screw device 1 on the string of drill pipe 2 is lowered into the well 3 to the calculated depth. At the mouth, the tubing is tied with a cementing unit pump (or a drilling rig). The first component of the mixture 4 — the buffer fluid and the second component — are pumped into the pipes successively and forced into the annular space and the drill string at specified intervals.

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mixtures 5. Then the screw is installed above the section of absorbing reservoir I, allocated for -isolation, and is driven into rotation by the drill pipe. After pumping a portion of the volume of the cement mixture into the first absorbing section, the tool is lifted and set at the next depth to isolate section II. According to this technological scheme, interval insulation of the entire thickness of the absorption zone from the base to the roof is performed.

The intensity of mixing of the components of the cement slurry, the flow rate and pressure of the mixture into the absorption channels are controlled by the frequency of rotation of the screw device, the limits of which depend on the combination of the dimensions of the well and the drill string.

If necessary, the adjustment, mixing and injection modes of cement slurries are performed by pumps of the cementing unit or drilling rig, as well as the use of downhole engines of low and high speed turbo drills in the layout of the downhole engines.

Example. To isolate the absorption in the range of 2000–2050 m, the screw on the string of drill pipe is lowered and installed at a depth of 2000 m. In the string of drill pipe, 10 m of gel-cement mortar, 1.0 m of buffer clay and 3.0 m of 1% are sequentially injected. an aqueous solution of polyacrylamide.

The placement of the first component in the annulus and the second in the pipes above the screw device is performed by pumping 25.0 m of mud into the drill pipe string (drill pipe diameter is 0.146 m). After that, it is lowered, installed at a depth of 2025 m — 25 m above the absorption base, and the rotation of the drill pipe string is activated by a 1.0 rotor. For a given rotation mode, mixing of the components of the cement

the solution and injection into the permeable section with a thickness of 25 m are performed within 10 minutes, with an average flow rate of 0.105 m3 / min. The insulated area receives 1.05 m of a mixture of gel-cement and polyacrylamide in a ratio of 3.4: 1, respectively, with a concentration of the reagent at a structure expander of 0.32%.

During this time, the fluid level in the well decreases by 90 m and the hydrostatic repression on the roof of the absorption decreases by 1.12 MPa.

(density of washing liquid 1.25 t / m). Then, the screw is lifted and installed in the absorption roof at a depth of 2000 m. The processing operation is repeated with mixing of the remaining components in the tubular and annular spaces and forcing the cement slurry into the absorbing interval I - II.

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5 After the end of the operation, the tool is lifted by 300-400 m and after 20-30 min. Of exposure for the formation and strengthening of the structure of the mixture, the circulation is restored.

0 drilling mud. Then, the mouth is sealed and pressed with pressure by the barrel, according to the permissible value of which the results of the isolation operation — reduction of the injectivity coefficient — are evaluated.

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Claims (1)

Invention Formula A method of isolating absorbing formations in wells by successive injection of components of cement mixtures, placing the latter in the absorption zone, mixing and pumping into the formation under pressure, characterized in that, in order to increase the efficiency of the isolation process, after placing the mixture components in the absorption zone the mixing and the injection is carried out in selectively separated areas in the turbulent flow by rotating the screw with a frequency of 0.5-10.0 and then moving it in the absorption zone from the bottom to the roof. Li l five 4 1