Experimental Investigation on the Conductivity of Micro-Frac Dynamic Proppant Transport Process

ABSTRACT: Fractures are primary flow channels of unconventional oil and gas reservoirs; thus, hydraulic fracturing is widely used to promote the productivity of unconventional formations. Hydraulic fracturing can induce numerous tiny fractures and stimulate some weekly cemented natural fractures. Since the width of the induced fractures is less than 200μm, large size proppants (less than 140 mesh) could not be transported and propped the tiny fractures efficiently. This paper proposed a dynamic proppant transportation and conductivity test method to investigate the flow resistance of the propped tiny fractures. Silica powder, tiny glass beads, and TBA powder were considered potential proppants that could be used to prop the tiny fractures. Proppant diameter and crushing ratio were evaluated. The conductivity of the tiny fractures was evaluated at various slurry concentrations and closure stresses. Results showed that the optimal slurry concentration should not be higher than 9%. Silica powder can be used in higher fracture closure stress formations while TBA and tiny glass beads are more suitable for propping tiny fractures under lower fracture closure stress conditions. 1. INTRODUCTION As more wells are drilled and completed in the tight formations, operators rely more on small-sized proppants to help ensure the created fractures are propped and to maintain the conductive flow paths for the well production. Micro-proppants may refer to proppants smaller than 100 mesh, mainly including silica flour and ceramic micro-proppant, fly ash are also available. In 1998, Standard oil applied 100 mesh grains of sand as propping agents in the Upper Morrow formation. Recent studies show that proppants that are smaller than 100 mesh proppants could further improve the permeability of unconventional reservoirs. It was also proposed that microproppant enjoyed a proppant transport benefit into complex fracture systems, in areas where 100 mesh and 40/70 could not travel. Dahl et al., (2015) undertook permeability tests on split core samples to investigate the effect of micro-sized proppants and tackifying agents in improving secondary fracture conductivity,