A New Method for Designing the Bridging Particle Size Distribution for Fractured Carbonate Reservoirs

Abstract

Summary Possessing a strong heterogeneity of fracture space; fractures, in carbonate reservoirs are well developed. Because of the frequent occurrence of lost circulation during the drilling procedure, the matching of the particle-size distribution (PSD), which is the plugging material with the fracture space, becomes the key to forming bridges and improving plugging capacity. To improve the matching between the PSD and the crack width, the surface response optimization method is adopted to determine the optimal PSD (OPSD) of lost circulation materials (LCMs) and plot the effective plugging data points in the ternary diagram. To simulate the multiscale fracture distribution in a wellbore, a multislit plate plugging apparatus (PPA) is used to evaluate the leakage of plugging materials with different PSDs. The PSD test results show that the OPSD has a multipeak structure, which is conducive to plugging cracks of different sizes. Compared with the ideal packing theory, this method, conducive to the later removal of the plugging material and recovery of carbonate reservoir productivity, is more applicable to fractured carbonate reservoirs and testing the involving oil, also to estimate the acid dissolution of the plugging layer, which shows that the dissolution percentage of the plugging layer is 95.9%. Hence, it is able to achieve the reservoir protection effect. The field application indicates that the new method possesses the capability to effectively prevent the leakage of small- and medium-sized fractures in carbonate reservoirs, which ensures safe and effective drilling.