Experimental Investigation on the Fracture Conductivity Behavior of Quartz Sand and Ceramic Mixed Proppants

[Image: see text] In this paper, a series of fracture conductivity experiments were designed and conducted by an American Petroleum Institute (API) standard fracture conductivity evaluation system. The mixing proportion of quartz sand and ceramic was optimized. By the evaluation of the proppant breakage rate and sphericity analysis of mixed proppant with different sand volume proportions (P(S)), the proppant mixture conductivity evolution behavior was analyzed. Results of this study showed that the conductivity of mixed proppant was between that of pure ceramic proppant and pure quartz sand proppant under the same conditions. For 20/40 mesh mixed proppant, a small amount of ceramic (25%) in mixed proppant could obtain 1.27–3 times higher conductivity than pure sand, while 40/70 mesh mixed proppant required the addition of 50% or more ceramic. The crushing resistance of mixed proppant determined the decrease of conductivity with the increase of effective closure stresses. A logarithmic empirical model was further derived from the results, which could be used to forecast the performance of fracture conductivity at different effective closure stresses and sand volume proportions.