METHOD OF WELL CONSTRUCTION IN COMPLICATED MINING AND GEOLOGICAL CONDITIONS FOR DRILLING AND DEVICE FOR ITS IMPLEMENTATION Russian patent published in 2014 - IPC E21B33/13 

FIELD: oil and gas industry.

SUBSTANCE: well construction method includes drilling and cementing of drilling direction and surface casing, penetrating the interval of unstable argillaceous deposits prone to sloughing and collapsing, predrilling of the underlying area with non-sloughing rocks to a small distance, performing a battery of geophysical studies, multi-stage cementing of the well. At first cementing of the first stage is made - cementing of the unstable argillaceous deposits with the underlying area with non-sloughing rocks, at that run in of the casing section is made at a tubing string using a device consisting of a locating bushing with side wash ports to cut cement slurry excess upon cementing and connection left thread at the lower end with which a staged adaptor is connected with concentrically set shell that protect from cement slurry coming to its walls. The adapter is connected to the upper end of the cemented casing string through a cross-over shoe, inner diameter values of the adapter and cross-over shoe is selected so that they are equal to outside diameter of the casing string. Upon cutting and washing of cement slurry excess, when cementing operation is over, the drilling stem with a coupling is screwed from the adapter and lifted to the surface. Upon waiting on cement (WOC) the second stage of the well bore cementing is performed - a part of the well bore placed above the cemented first stage - using a device for multi-staged cementing by connection of the cross-over shoe with cementing ports blinded by removable plugs, to the lower end of the pipe at the casing with diameter equal to the diameter of the casing cemented at the first stage. To the lower end of the device frame a staged adapter is fixed with a drilled shoe at the lower end and return valve. Outside diameter of the adapter is selected with value equal to inner diameter of the adapter of the locating bushing of the device at the first stage of cementing and its inner diameter, diameter of gates and frame is selected as equal to the inner diameter of a pipe of the cemented casing. Running in of the casing pipe is made before setting of the butt end of a larger stage of the adapter to the inner protrusion placed under adapter connecting thread of the locating bushing at the first stage of cementing. Upon completion of cementing and WOC the top cementing plug with a saddle, shoe and cementing plugs made at the first stage of cementing are drilled out and further deepening of the downhole up to the design mark is made with a bit having less diameter.

EFFECT: accident free hole making, reduction of material costs and time for the well construction.

4 cl, 7 dwg