Overall cementing technologies used for shale gas wells in Jiaoshiba block

The marine shale gas wells in Jiaoshiba block is now the focus of SINOPEC'S exploration and development. In this block, caverns, pores and fractures are developed and associated with shallow gas in the upper strata. In the lower strata, micro-fracture permeable circulation loss happens and gas layers are active, so the conflict between circulation loss and pressure stabilization is obvious. It is difficult to guarantee the cementing quality of long horizontal sections in the surroundings of oil-based drilling fluids. And wellhead pressure is induced for set cement is seriously damaged during large-scale fracturing. To deal with these difficulties, a series of overall cementing technologies suitable for Jiaoshiba block were established by optimizing the setting depth of conductors, developing high-intensity low-density cement slurry system and tough cement slurry system, adopting controllable gel plugging technology and applying well cementing technologies (e.g. circulation loss prevention, pressure stabilization and displacement efficiency improvement). And consequently cementing quality is improved, satisfying the development requirements of Jiaoshiba block. The research results can be used as the reference for well cementing of the same type.