DRILLING FLUID FOR FLUSHING OF LONG-DISTANCE STEEPLY INCLINED WELLS UNDER CONDITIONS OF PERMAFROST AND HIGHLY COLLOIDAL CLAY ROCKS, AND ITS APPLICATION METHOD Russian patent published in 2013 - IPC C09K8/20 

FIELD: oil and gas industry.

SUBSTANCE: drilling fluid for flushing of long-distance steeply inclined wells under conditions of permafrost and highly colloidal clay rocks contains the following, wt %: clay powder 0.80-2.00; biopolymer KK Robus 0.08- 0.35; polyanionic cellulose PATS V 0.12-0.55; water-repellent fluid Sofeksil 40 0.10-0.70; lubricant KSD 1.50-10.00; water 87.79-96.20; barite weighting material 4.50-144.00 above 100. Application method of the above drilling fluid consists in the fact that the above drilling fluid with density of 1360-1420 kg/m³ is prepared for a drilling operation. It is injected into the well by being used during the drilling operation for the direction; after that, four-stage mechanical cleaning from the drilled-out rock of waste drilling mud from under the direction is performed. It is diluted with mineralised water by 2.5 times till the density is 1136-1155 kg/m³. Technological parameters of the obtained solution are measured and brought to design values by additional treatment with a number of reagents and till the ratios of the first above solution. Then, the obtained solution is injected into the well by being used during the drilling operation for the conductor; after that, four-stage mechanical cleaning from the drilled-out rock of waste drilling mud from under the conductor is performed. It is diluted with mineralised water by 1.7 times till the density is 1070 kg/m³, technological parameters of the obtained solution are measured and brought to design values by additional treatment with a number of reagents and till the ratios of the first above solution. It is used for drilling under an intermediate and production string. Then, four-stage mechanical cleaning from the drilled-out rock of waste drilling fluid is performed again. It is treated with barite weighting material till the density is 1800 kg/m³, its technological parameters are measured and brought to design values by additional treatment with a number of reagents and till the ratios of the first above solution. That solution is used for drilling under the shank.

EFFECT: creation of polymer-clay solution with pseudoplastic properties and controlled density to maintain stability of the well walls under conditions of permafrost formations complicated with gas-hydrate accumulations, enlarging the area of its application for drilling of intrapermafrost intervals composed of highly colloidal clay deposits due to additional provision of high inhibiting, lubricating properties; reduction of water consumption volumes, drilling wastes and consumption of reagents.

2 cl, 4 tbl, 2 dwg