THE EVOLUTION OF PROPPANT DISTRIBUTION IN A MULTISCALE FRACTURE PROCESSED ZONE

In an effort for a better diagnosis of post-fracturing performance, studies of proppant transport in activated natural fractures and induced secondary fractures have been increasingly receiving attention due to nature of the complex geometry and stress evolution mechanisms. The fracture surface roughness in the fracture network has been shown to violate the assumption of constant flow path during proppant transport, and hence a dynamic fracture conductivity study is desired. In this study, we introduce a 3-D displacement discontinuity (DDM) method coupled with computational fluid dynamics simulation for the investigation of proppant transport and conductivity in the main fracture. Surface roughness and jointed secondary fractures are also considered in this complex fracture network under the fracture processed zone (FPZ) system.

The objective of this study is to investigate the effect of settling proppant to the evolution of fracture conductivity in the main/secondary fractures with present surface roughness by tracking particle settling distribution. The sensitivities of fracture conductivity to surface roughness and incorporation of secondary fractures are examined. In this work, fracturing fluid, as the proppant carrier, is mixed with regular proppant (100 +-25 Mesh) and micro-proppant (225 +-100 Mesh) targeting both the main and secondary fractures in a field-record-guided schedules.

In particular, CFD simulation with appropriate laminar/turbulent flow models are conducted in parallel with the suspension flow experiment. It captures the essential nature of the dispersed phase slippage in continuous medium in the fracture plane geometry with nonzero roughness. For the flow mechanism in secondary fractures, a multi-continua flow model is introduced to accommodate the scaled geometry. Results from this study reflects the critical role of the fracture plane roughness to both conglomeration and self-traveling proppant particles scenarios. The presence of secondary fractures causes additional leakoff; but this issue can be resolved by the appropriate placement of the micro-proppant.

This work provides a preliminary guide to maximizing the overall post fracturing performance and stimulating reservoir volume utilization.