Drilling and completion operation practice of first multilateral horizontal well in Qinghai Oilfield

In order to further increase the production output per well, Qinghai Oilfield plans to use the double multilateral horizontal well mode to exploit the base-ment gas reservoir in Dongping. In consideration of the technical difficulties existing in this area, such as relatively serious leakage in drilling operation, hard mudstone at the window-opening position as well as the slice mining requirements brought forth by first party, and through optimization of wellbore structure, proper selection of multilateral well drilling and completion program, positioning process, window opening process, whipstock recovery, re-entry and selective mining process and supporting tools, these technical difficulties have been settled, and the multilateral well drilling and completion technology applicable to development of Base-ment oil-gas reservoir has been formed. In the field application, the completion operation of such well has been completed smoothly. After being put into service, this well has got the daily gas production of 76×104 m3, becoming the well with the highest production output in Qinghai Oilfield over 60 years. As a result, the expected effect has been achieved, and a new technical approach for highly-efficient development of base-ment gas fields has been found.