Research on Cementing and Loss Prevention Drilling Fluid Technology During Drilling in the Sea Basin

This paper analyzes the geological features and drilling fluid loss situations in the China's Sea Basin, identifying the challenges in leak prevention and plugging technology in this area. These include prevalent formation fractures with micro to millimeter-scale multi-scale cracks, and even the coexistence of fractures and cavities, which pose difficulties in choosing appropriate plugging materials and lead to a low success rate for first-time plugging. Moreover, there are extensive sections of weathered crust in the formation, coupled with highly developed fractures and severe fragmentation in some strata, resulting in secondary development of fractures, critical fluid loss or even non-return fluid loss. In response to these challenges, this paper synthesizes a type of gelation plugging agent, BFD-1, using polyvinyl alcohol, polypropylene acid, and organics with hydroquinone structures as raw materials. Experimental results show that the compressive strength of the artificial loose rock core increased by 19.34% after being soaked in 4% BFD-1 aqueous solution. Based on BFD-1, field plugging materials were combined to create drilling fluid systems for leak prevention and plugging for lost channels with different size. The drilling fluid exhibits excellent circulation-lost-control and cementing capabilities, and effectively prevents pressure transmission. The research results provide support for the subsequent lost-circulation control technology in this area.