The influence of acidizing on propped fractures for productivity enhancement: Eagle Ford laboratory study

Abstract

Hydraulic fracturing of tight formations and placing proppants within induced fractures are commonly performed in unconventional shale reservoirs all over the world, especially in North America. However, the overall recovery of these oil and gas resources is very low and hence, production enhancement is inevitable.This study investigated the acidizing of propped fractures as a recovery enhancement method in Eagle Ford shale samples. Experiments were designed using sample slabs having proppants between them. Differing parameters were examined to optimize the fracture conductivity through acidizing. For a range of confining pressures, the fracture conductivity was maximized by minimizing the proppant embedment. A higher acid injection rate was achieved with a 5 % HCl concentration. Proppant concentration and proppant size were found to affect fracture conductivity inversely. However, this trend was not observed to be monotonic. In terms of production parameters, the skin factor determined the optimized conditions at a constant confining pressure. Overall, the optimum conditions for acidizing in the propped fractures were determined while having 5 % HCl concentration, 1 lb/ft2 (4.88 kg/m2) proppant concentration, 600–710 μm of proppant size and 8 ml/min acid injection rate. These findings confirmed the applicability of the method for hydraulic fracturing optimization in Eagle Ford shale samples. It can also be regarded as a primary enhancement method due to its low cost and the process simplicity in comparison to hydraulic fracturing operations. The experimental results of this study would correspondingly enlighten their potential field applications through facilitating appropriate modification with regards to specific operational conditions.