Method for cementing compaction for gas wells. RU patent 2506407.

FIELD: oil and gas industry.

SUBSTANCE: invention is related to gas industry and it can be used during remedial cementing of gas and gas condensate wells in operation process in order to compact and recover gas permeability of cementing and namely cement sheath. Carbon dioxide is used as a reagent in the method of cementing compaction for gas wells that includes treatment of cement stone by reagent pumping to annular space thus forming insoluble or hardly soluble residue at interaction with calcium hydroxide of cement stone with further creation of supplementary pressure; at that treatment of cement stone is implemented at gas intake capacity from 0.1·10^-3 up to 6.7·10^-3 m³ /(h·MPa) and zero water intake.

EFFECT: ensuring gas permeability for tubing-casing annulus with non-availability of water intake.

1 tbl

The invention relates to the gas industry and can be used in the repair and isolation works (RIRs) in gas and gas-condensate wells in the process of operation for the seal and recovery lining, namely cement ring.

Currently extensive experience of RIR for the compaction of the lining of gas and gas-condensate wells elimination of leakage of the cement ring.

Works on restoration of cement rings are defective insulation gap by injection under pressure of various clog and clogging of reagents.

The main criterion for selection of the insulation material is the state of the cement stone insulated interval well, characterized by such indicators, as the specific pickup well for downloading of liquids or gases, which is determined before the holding of the RIRs.

There is a method of sealing the lining of gas wells, which includes the processing of cement by injection into the well annulus of electrolyte solution (RF patent №2213203, 7 IPC 21 33/138, Z. no 2001130222, priority 08.11.2001, publ. 27.09.2003).

Also known way to eliminate annular in the well, including the injection of a viscous solution into the well annulus (RF patent №2166614, 7 IPC 21 33/138, Z. no 99119768, priority 14.09.1999, publ. 10.05.2001).

In the known methods due to the high viscosity of my compositions and, in this regard, insignificant depth of penetration, reducing the efficiency of the recovery tightness of cement stone.

Also known way of sealing channels in column spacing of wells, including filling of channels insulating composition containing urethane , the first pump gaseous agent full replacement of the liquid phase of channels, and then produce a filling these channels hydrocarbon anhydrous liquid with a low viscosity and high penetrating power, then pump the solution urethane , then pumped hardener (RF patent №2277626, IPC 21 33/138, Z. no 2004135660, priority 06.12.2004, publ. 10.06.2006).

The disadvantage of this method is the low penetration depth clog compositions, which reduces the efficiency of a method.

Closest to the claimed technical solution for the totality essential sign is a way to seal the lining of gas wells, which includes the processing of cement by injection into the well annulus reagent water electrolyte solution with the subsequent creation of additional pressure, as a reagent used solution of inorganic salts, forming insoluble or trudnorastvorimy sediment in the interaction with calcium hydroxide of a cement stone, for example, solution of aluminium sulphate concentration in 9,0-23,0% moreover, additional pressure created not earlier than 2 hours after injection of inorganic salts (RF patent №2166613, 7 IPC 21 33/138, Z. no 98118177, priority 02.10.1998, publ. 10.05.2001, prototype).

The disadvantage of this method is the complexity of preparation of a solution of aluminium sulphate, due to weak soluble reagent at low temperature (requires water heating up to +90 degrees C), and the inability to use when no pickup annular space (ITUC) on water.

Objective of the proposed technical solution is to ensure annular space with the lack of permeability of water.

The specified task in the present method seal lining gas wells, which includes the processing of cement by injection into the well annulus reagent, forming insoluble or trudnorastvorimy sediment in the interaction with calcium hydroxide of a cement stone, with the subsequent creation of additional pressure, decides that the processing of a cement stone is carried out at a pickup gas from 0.1·10 -3 to 6.7·10 -3 m 3 /(h·MPa) and zero pickup on water, and as a reagent use carbon dioxide.

Difference of the proposed method from the above, the most close to it, is that the processing of cement stone is carried out at a pickup gas from 0.1·10 -3 to 6.7·10 -3 m 3 /(h·MPa) and zero pickup on water, and as a reagent in the annulus is injected carbon dioxide.

For operational wells at full absence of permeability of water recovery lining, namely cement ring in annular spaces by using carbon dioxide.

The authors experimentally found that the interaction of carbon dioxide with the main mineral cement stone - calcium hydroxide happens carbonization of cement according to the scheme:

Ca(OH) 2 +CO2 →CaCO3 embed+H 2 O

This forms a precipitate of calcium carbonate, which is under pressure clog cracks and pores of the cement stone, restoring its integrity.

Pressure pumping carbon dioxide is determined by the formula:

P C =·P ITUC <P DOP ,

where P C - pressure gas injection, MPa;

K - coefficient taking into account the increasing pressure to overcome when suppressing the resistance of the fluid located in the cement stone, with K=1,5-2,0;

P MCP pressure at the mouth in column spacing, MPa;

P DOP - allowable pressure, which is resistant to the wellhead equipment or pipe casing, MPa.

Carbon dioxide is injected under pressure, which exceed the initial pressure, but no more valid.

Thus, the claimed combination of technological operations for the densification of the lining of gas wells ensures the achievement of the new the technical result obtained from the use of the distinctive signs and lying in ensuring the penetration of carbon dioxide deeper into the pores and cracks of the cement stone, inaccessible to any liquid (as pick-up water is absent), where due to the flow of the reaction of interaction with the calcium hydroxide is formed calcium carbonate, which is sealed under the action of high pressure and pores and microcracks cement stone, restoring inter-casing gas-tight space.

Known to use carbon dioxide as the dispersed gas phase in the way of free gas inflow isolation in the hole (application for invention №2001107412, 7 IPC 21 43/32, priority 21.03.2001, publ. 20.02.2003).

In the specified method of carbon dioxide is used as dispersed gas phase for the preparation of water-oil emulsion with additives, surfactants used to isolate the flow of free gas from a reservoir.

From the available sources of scientific-technical and patent information about technical solutions containing signs that match the distinctive features of the claimed invention, and giving the same technical result, it is not revealed. This allows to make the conclusion about conformity of the proposed technical solution criterion of «inventive step».

Research insulating properties held by the generally accepted method of measuring the acceleration of samples before and after injection ( .. and other Workshop on the physics of the oil reservoir. M, ed. MINH and SE, 78 BC).

Insulating effect of The is determined by the formula:

K =(1-To 2 /1 )·100%,

where To 1 - pickup before treatment,

2 - pick-up after treatment.

To assess the effectiveness of the proposed technical solutions were carried out laboratory researches. Checking the insulating effect was carried out on specially assembled installation on samples of cement stone.

Example. Formed samples of cement stone, which have the form of a truncated cone with the diameter of the grounds 44 and 38 mm and a height of 76 mm zero-responsive water and responsive rate from 0.1·10 -3 to 45.0·10 -3 m 3 /(h·MPa). Then, each sample was saturated with carbon dioxide under pressure of 0.1 MPa for two hours, after which the gas supply was stopped and left the samples for 24 hours for reaction. Upon expiration of this period was performed using helium check pickup treated carbon dioxide samples. The results of the research are reflected in the table.

Pick-up on gas, m3 /(h·MPa)

Insulating effect, %

After recovery

0,1·10 -3

0,4·10 -3

0,78·10 -3

0,9·10 -3

6,7·10 -3

10,0·10 -3

2,0·10 -3

20,0·10 -3

2,6·10 -3

45,0·10 -3

5,7·10 -3

By reviewing the results of research, data are reflected in the table shows that for a pick-up from 0.1·10 -3 to 6.7·10 -3 m 3 /(h·MPa) insulation effect is 100%. When injectivity of cement for gas less than 0.1·10 -3 m 3 /(h·MPa) is instantaneous clogging of the pores of cement stone. When values of injectivity of cement for gas more than 6.7·10 -3 m 3 /(h·MPa) gradual destruction of cement due to its corrosion of carbon dioxide, increasing the porosity and permeability.

Shutoff reagent according to prototype upload in these samples of cement similar conditions could not because their pick-up water is absent.

In industrial conditions the method is implemented as follows:

- is determined by the excess pressure at the mouth of the ITUC wells;

- is venting the pressure of the MCP;

- defined acceleration on the water;

- in the absence of permeability of water to the mouth of the well connected via a gear cylinder with carbon dioxide;

- is purged from excess water and sealed the mouth of the well;

- the ITUC injected carbon dioxide under pressure, which should be 1.5 to 2.0 times exceed the initial pressure, but not more than permissible;

- drop the pressure in the cylinder is determined by the volume of injected gas;

- in the absence of a drop in pressure in the cylinder flow of carbon dioxide in the IPC stop;

- then create additional pressure 1.5 to 2.0 times greater than the initial pressure, but not more than permissible;

- well in this position left for 24 hours for the reaction of carbon dioxide with calcium hydroxide;

- after the specified time are grazing pressure in the ITUC and is determined by the flow of fluid from the ITUC;

- in the absence of receipt of a fluid is crimp ITUC carbon dioxide at pressure that doesn't exceed the rated pressure.

- provides penetration of insulating agent (carbon dioxide) in the cement stone to greater depth;

- achieved recovery cement zero pickup ITUC and water permeability of gas from 0.1·10 -3 to 6.7·10 -3 m 3 /(h·MPa);

- is to simplify the process by delivering gaseous reagent, not a solution of salt, that you must first prepare the necessary concentration.

The use of the proposed method seal lining gas wells allows to ensure a gas-tight annular space with zero-responsive water.

Packing method lining gas wells, which includes the processing of cement by injection into the well annulus reagent, forming insoluble or trudnorastvorimy sediment in the interaction with calcium hydroxide of a cement stone, with the subsequent creation of additional pressure, characterized in that the processing of a cement stone is carried out at a pickup gas from 0.1·10 -3 to 6.7·10 -3 m 3 /(h·MPa) and zero pickup on water, and as a reagent use carbon dioxide.