Anti-Collapse Drilling Fluid Technology for Broken Carbonate Formation in Shunbei Oil and Gas Field

In order to solve the problem of wellbore collapse in broken carbonate formation of Ordovician in Shunbei Oil and Gas Field, this paper analyzed the cause of wellbore collapse from the characteristics of geological structure, the development and filling of fractures in the formation, and the stress on the wellbore block. It was found that the stress concentration in the strong compression section, the development of micro fractures in the formation and the influence of gravity on the directional interval were the main causes of wellbore collapse. According to the analysis, since the formation fragmentation and stress concentration could not be changed, the problem of wellbore collapse could only be solved by improving the plugging performance of the drilling fluid through effective filling and plugging of micro fractures, preventing the transmission of pressure and maintaining a high density for stress support. Therefore, the anti-collapse drilling fluid was prepared from the aspects of strengthening the plugging ability, controlling the filtration at high temperatures and pressures, optimizing the yield point and plastic viscosity ratio of the drilling fluid, etc., so as to improve its anti-collapse performance. The field test of Well Shunbei X showed that after adopting this anti-collapse drilling fluid technology, the drilling torque was stable, the ROP was high, the hole diameter enlargement ratio was small, and the anti-collapse effect was good, which could provide reference for efficient and safe drilling under the similar conditions.