Wellbore Stabilization Technology for Fractured Formation in Shunbei No.5 Fault

Abstract

Basic geological background, drilling fluid formulation optimization and field application were carried out aiming at the technical problems of multiple blocks in Shunbei Oilfield when collapsing strata and collapsing and blocking frequently. The lithology of the fracture zone is non-clay minerals. After the drilling fluid or filtrate is eroded, the self-developed pore network is easily pressurized and connected, which reduces the adhesion of the bedding interface, which in turn induces large-scale spalling and slump stuck. Based on the mechanism of the instability of the borehole wall, a submicron-micron (0.1-100μm) comprehensive and effective plugging is proposed to prevent drilling fluid or filtrate from invading the formation pores and fractures around the well, and at the same time ensure that the drilling fluid has an efficient rock-carrying solution. The technical achievements carried out on-site tests at Shunbei No. 5, based on the original Sikai high-temperature polysulfonate drilling fluid, optimized the indoor formulation, and developed a wellbore stable drilling fluid suitable for broken formations. During the application process, there were no drilling accidents such as block blockage, which was the shortest record of drilling time in the reservoir section of the block.