Technologies for Snubbing Services in Horizontal Shale Oil Wells in the Cangdong Sag

The shale oil reservoir in the Kong-2 member of the Cangdong Sag has ultra-low porosity, ultra-low permeability and high shale content, and thus, it is prone to be contaminated by invasion of fluids including killing fluid during operations. Regarding this problem, the sucker rod pumps, the lift technology of electric submersible pumps, and the associated production string and downhole tools commonly used in shale oil wells were optimized. Then, the technologies for snubbing services in the horizontal shale oil wells in the Cangdong Sag were formed with snubbing service with prefabricated inner blowout preventers, completion with controllable bridge plugs that can temporarily close wellbore, and under-pressure pumping-down operation with cable-laying coiled tubing. Field applications showed that this technologies could successfully address the problems such as lined tubing sealing failures of sucker rod pumps and under-pressure operation failures of electric submersible pumps,etc. After the operations, the reservoir was not contaminated and the pumping-down operation were free from waiting for complete pressure relief.