An Experimental Study on optimizing the particle size distribution of bridging agents in drilling fluids

Abstract Managing lost circulation has always been a serious challenge in the oil industry. This situation becomes further complicated when shale formation is involved. Particulate lost circulation materials (LCMs) have been used to prevent the drilling fluid from entering fractured, cavernous, or high-permeability formations for many years. However, existing LCMs are inefficient in terms of size and application methods in solving severe-to-total losses in shales due to the uncertainty of particle size distribution (PSD) in drilling fluids. This study focuses on an experimental method optimizing the PSD of solid particles in the drilling fluid at high temperature and pressure. An orthogonal experiment of L9 (3)4, including four factors and three levels, was designed to investigate the relationship between the PSD of solid particles and filtration loss. Results indicate that the orthogonal design method contributes to the optimization of the PSD of solid particles in the drilling fluid and reduce the test time and experimental workload during the drilling fluid process in the design stage. In addition, a polynomial relationship between the cumulative filtration loss and D90 or D50 is verified experimentally in this study. This study will remarkably benefit the drilling technologists in resolving the issue of lost circulation.