SU1213177A1 - Method of plugging absorbing and water-bearing formations - Google Patents

Description

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

The purpose of the invention is to increase the efficiency of tamping of layers by increasing the uniformity of mixing of the cement slurry with the accelerator, setting it and reducing the consumption of the latter.

Experimental data show that an aqueous solution of accelerator setting and hardening, filtered through cement mortar with a pressure drop of 0.5-1.5 MPa, interacting with the mortar, leads to the formation of cement stone in a short time (30 min), strength the compression of which is 0.30-0.73 MPa.

Filtration of the accelerator solution through the cement slurry under porous conditions with a drop of less than 5 MPa does not ensure the setting and hardening of the cement even for 30 minutes. At high pressure drops, for example, 0 MPa, the accelerator solution erupts at the contact of the cement slurry — the wall of the chamber and the stone is non-uniform and fragile.

The method is carried out as follows.

On the filling pipes, the packer is lowered into the well and installed at a predetermined depth. Cementing aggregates are connected to the casting pipes, with which the casting tubes are filled with components of the cement mix: cement mortar, separation buffer liquid, aqueous solution of the accelerator setting and hardening. Cement mortar pushes into podpaperno space, and then into permeable rocks. Following the cement mortar without a break in time, the separation buffer fluid is forced. A high viscosity mud is used as a separation buffer. After the buffer fluid is supplied to the permeable zone, the accelerator is set on the setting time and hardening time. To ensure transportation of the components of the cement mix in the absorption zone and filtering the accelerator

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through the cement slurry into the channels of permeable rocks, the injection rate is controlled by the magnitude of the allowable excess pressure of 0.5-1.5 MPa in comparison with the pressure of the cement slurry.

If it is impossible to create a pressure drop of 0 MPa during isolation of permeable rocks in the initial period of injection, which is determined by the results of hydrodynamic studies, the calculated volume of mud with a filler (soft tampon) is pumped into the isolated area to increase hydraulic resistance and create the required pressure drop for effective filtration of the accelerator through the cement mortar.

Example. Standard cement cement, shuttered in a volume of 15 m, is pumped into the casting pipes, then, without a gap in time, 2 m of separation buffer fluid — clay mud of increased viscosity (to non-flowing) viscosity — is pumped. Following the buffer fluid, 5.0 m of a 10% aqueous solution of the accelerator for setting and hardening of a tense-liquid glass are pumped into the pipes, followed by a calculated volume of 8.0 m (for a depth of 1000 m of a diameter of 127 mm pipes) - clay mud. In order to ensure the normal conditions of transportation of the components of the cement mix to the absorption zone and to effectively mix them in the channels of permeable rocks, the injection rate is controlled by the value of the allowable push pressure.

The adjustment of the permissible limits of change in the discharge pressure drop during the operation is carried out by varying the pump performance of the cementing unit.

After completion of the operation of squeezing and mixing the components of the mixture in the absorbing channels of the rocks, the instrument is kept at rest for 20-30 minutes, and then the packer is torn off and the tool is removed to the surface. Without stopping to wait for the mixture to harden, the drilling of the well begins.

The volume of the accelerator solution required for a drastic reduction in the time required for the formation of cement stone is from 20 to 100% of the volume pumped into the permeable rocks in the shear and depending on the accelerator activity.

Claims (2)

1. METHOD OF TAMPONIZING ABSORBING AND WATER-GIVEN LAYERS, including injection of plugging solution and its pushing into the formation, subsequent injection of the accelerator for setting the plugging solution and its pushing into the formation, characterized in that, in order to increase the efficiency of plugging of the formations by increasing uniformity the accelerator of its setting and reducing the flow rate of the latter, the pushing of the accelerator of setting the plugging solution into the formation is carried out in the filtration mode through amponiruyuschy solution. 2. The method according to π. 1, characterized in that cement mortar is pumped as a plugging solution, and liquid glass is used as an accelerator for setting it, and the latter is forced into the formation at pressures of 0.5-1.5 MPa greater than the cement mortar.