Laboratory investigation of the selection criteria for the particle size distribution of granular lost circulation materials in naturally fractured reservoirs

This paper presents a new criterion for selecting the particle size distribution (PSD) of granular lost circulation materials (LCMs) in naturally fractured reservoirs. A comprehensive laboratory investigation was conducted on a plugging setup with extended simulated fractures. Comparative experiments show that the API test method might fail to distinguish mouth sealing and throat plugging of a fracture, and the well-known selection criteria have poor adaptability to the natural fractures. The new criterion ensures that LCMs build a stable and tight plugging barrier inside the fracture. It found that the ratio of characteristic particle size (D90) to fracture opening (WA) should range from 0.5 to 0.7; the relative particle size span (Sp) should be greater than 1.5, and the characteristic particle size (D10) should be between 0.1 and 0.2 mm. The proposed selection criterion showed a 90% coincidence rate between the predicted and measured plugging test results. •The well-known selection criteria have poor adaptability to the natural fractures.•New selection criteria for particle size distribution are proposed and validated.•The new criteria allow LCMs to form a stable and tight barrier inside the fracture.