PROCEDURE FOR WELL CONSTRUCTION Russian patent published in 2011 - IPC E21B7/00 E21B21/00 

FIELD: oil and gas production.

SUBSTANCE: procedure for well construction consists in drilling borehole under laminar-flow mode of flush fluid pumping through circular space of well borehole. A conductor is drilled under the laminar-flow mode of flush fluid pumping, further, it is cased and anchored and then the conductor is drilled under turbulent conditions of flush fluid. At occurrence of zones with unstable clay rock at operation under the laminar-flow mode the conductor is cased and cemented. The main borehole is drilled under the turbulent conditions. 5-20 m before a productive horizon of unstable clay rock the borehole drilling is performed under the laminar-flow mode; the well is after-drilled till a design mark, the main borehole of the well is cased and fixed with cement. Also, as flush fluid for the laminar-flow mode there is used fluid of viscosity not exceeding 50 s, while consumption of fluid is maintained not over 16 l/s at drilling with a bit of diametre from 530 to 217 mm, consumption not over 10 l/s at drilling with the bit of diametre from 217 to 155.6 mm and not over 7 l/s at drilling with the bit of diametre from 155.6 to 84 mm.

EFFECT: increased speed of borehole drilling.

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