An efficient stimulated reservoir area (SRA) estimation method based on octree decomposition of microseismic events

Abstract

Fracture contact area is the critical factor determining post-treatment production after multi-stage hydraulic fracturing. At present, there are no effective methods for the estimation of the stimulated reservoir area (SRA) of the complex fracture network after stimulation. Conventional methods mostly focused on calculating stimulated reservoir volume (SRV) by using microseismic events directly or indirectly. However, since there is a large number of noise events in microseismic data that can't be removed completely, the SRV results often have huge errors and are inconsistent with practical well production.For this reason, we propose an efficient and robust SRA calculation method based on 3D octree decomposition. The method is able to effectively estimate SRA by generating a multi-level grid structure without reconstructing the fracture network. Through a large number of case simulations based on synthetic events generated by Monte Carlo method, it is found that our method could adapt to the estimation of SRA for different configurations. It could obtain reliable and robust results in the presence of noise events. Specifically, it is indicated that the maximum relative calculation error is less than 20% for mesoscale and large-scale fracture network. The error for small-scale fractures could be reduced below 30% combining with the error reduction approach put forward in this paper. The applicability of our method is also investigated through two horizontal well platforms. Compared with the conventional SRV method, it is found that SRA obtained by our method could better reflect the stimulation effects and is more consistent with real production. It could become a potential and effective index for stimulation evaluation and fracturing operation optimization.