Experimental study on true triaxial pressure-bearing plugging in micro-fractured formation

The pressure-bearing capacity of the micro-fractured formation is low, and the leakage phenomenon is serious under the action of high-density drilling fluid. The pressure-bearing plugging can improve the pressure-bearing capacity of the formation that is vulnerable to leakage. In this paper, the sandstone outcropping was made into 295mm×297mm×300mm samples to conduct true triaxial pressure-bearing plugging physical experiments. The result shows:(1) Large granular lost circulation materials were accessible to accumulate around the open hole to form a dense mud cake, which greatly improved the pressure-bearing capacity of the formation. (2) Under the action of high pressure, the small granular lost circulation materials were rapidly pumped into the micro-fractured formation, forming a plugging layer in the fracture. (3) It was found that when increasing the plugging slurry injection rate, the plugging zone was more prone to instability, and the final pressure-bearing value of the formation was reduced. This study explored the plugging effect of lost circulation materials with different particle sizes and ratios on the fractures and optimized the corresponding construction parameters by carrying out true triaxial pressure-bearing plugging experiments in micro-fractured sandstone formations under different working conditions, in order to provide guidance for pressure-bearing plugging site construction of micro-fractured sandstone formations.