Abstract: In order to select the lost circulation material more reasonably and to design the high performance plugging slurry formulations,the retention behavior of different lost circulation material of various geometrical morphologies in the fractures was studied.Researchers combined theoretical analysis with laboratory tests,and took into consideratoin the influence of grain size grade of lost circulation material,geometrical morphology and fracture surface roughness.They then designed and carried out solid phase retention tests in the rough face fractures to investigate the effect of geometric shape of plugging material on its retention behavior(and embedment)in fractures was investigated.It was found that the grain size grade had an effect on the retention behavior of both spherical material and flaky material in fractures. In fact,the effect on the retention behavior of spherical material was more significant.Specifically,when the material was of the same grain size grade,the retention probability of the flaky material in the fractures was higher than that of the spherical material.The results showed that the spherical material had advantages,including its rapid plugging and high plugging efficiency.However,its plugging quality was seriously affected by grain size grade,and the adaptability to the variation of slot width was poor,while the advantages of flaky material were its strong adaptability to slot width variation and high retention probability.The combination of spherical lost circulation material and flaky lost circulation material could effectively improve the retention and embedment probability and achieve better fracture plugging.