Abstract
Microseismic monitoring technology is widely used to characterize the fracture network and provide enough information on fracture geometry and properties. We go beyond the existing method that uses planar fractures or orthogonal conjugate fractures for representing the fracture network. Our novel method of characterization involves an integrated workflow to utilize L-system based fractal geometry to describe fracture propagation pattern, density and network connectivity. Integer programming is incorporated into matching the origination points of the microseismic events during the fracture geometry matching procession. Furthermore, multilevel of the fractal fracture network model (FFNM) is calibrated by using genetic algorithm to help specifying the properties of fracture network. The additional rate transient analysis allows to interpret the relationship between well performance and complex fracture network features. The application of this workflow on unconventional shale gas start with calculating fractal fracture network geometry and determining fracture length for both hydraulic fracture and induced fracture. And also estimating stimulated reservoir volume (SRV) and fracture parameters with combination of production data. Field case study is presented for fractured horizontal well, the matching result shows that the fracture propagation path has a good fitness with microseismic event. We also carry out rate transient analysis to interpreting the performance of complex fracture network parameters. This indicates that only connected stimulated fractures does most of the contribution to gas production. The better connectivity of multi-level fracture network, the better performance of fractured well during long time development. Besides, the most significant new finding is that SRV increases as fractal fracture induced levels increase, and this relationship appears to be fracture geometry-dependent. The novelty of this new method is expected to become a more efficient process for accurate characterization of shale reservoir complex fracture network and improvement hydraulic fracture optimization.
