Application of relay-type device with no drilling and no cementing in cementing of lost circulation well

During the infill drilling in the second and fourth fault blocks of Gangxi Aera 1 in Dagang Oilfield, lost circulation often happens in the target layers.The faulted block oil reservoirs are located in Minghua and Guantao Formations with burial depth of 700-1 500 m.Oil layers are closely distributed in the vertical direction and many small oil layers are always developed in the depletion mode without energy supplementation, so the reservoir pressure is low with pressure coefficient of 0.85.And consequently, the pressure bearing capacity of target beds cannot satisfy the requirements of originally designed second-section cementing, and the subsequently cementing quality is impacted seriously.To improve cementing quality, the casing program for well completion of drilling free two-stage cementing was designed after the reasons for lost circulation were analyzed.The combination technology of relay drilling free two-stage cementing device and external casing packer with backing pin was researched and developed.By virtue of relay drilling free two-stage cementing device, the technical issues are solved successfully, such as two-stage cementing, coordination with the external casing packer with backing pin and drilling free.The qualified cementing rate is over 90%.