Statistical Analysis of Fractures from the Hydraulic Fracture Test Site 1

Which reservoir properties are most significant in optimizing hydraulic fracture propagation? In this work, we performed statistical analyses of hydraulic fractures along a slant core drilled in the Hydraulic Fracture Test Site (HFTS1) in the Midland Basin in West Texas. We combined these data with a high-resolution 3D reservoir model constructed to find the critical factors that control fracture initiation and propagation. The data collected from the HFTS1 has enabled us to build an accurate geomodel and perform statistical analysis of the associated attributes. The 3D reservoir model incorporates geological, geophysical, geomechanical, and production data from the HFTS1, following Dommisse et al. (2018)'s approach. The centerpiece of this model is 600 feet of core taken from the Wolfcamp A and B. This core passes by two horizontal producers on the 11-well pad and contains natural and hydraulic fractures that have been analyzed. Previous works have detailed the nature of the fractures recovered in the core, identifying 375 hydraulic fractures, 309 calcite-sealed natural fractures, and 8 faults (Gale et al., 2018). We studied the likelihood for fractures to be initiated or reactivated, compared to the reservoir properties and completion processes for neighboring wells. Analysis tools include Bluback Investigator and frequentist and Bayesian statistical inference libraries. The results of this work show hydraulic fracture initiation was dependent on the distance to the well and well productivity at the HFTS1 pad is highly varied. We have found that hydraulic fractures were less likely in highly naturally fractured rock. Of the three sets of natural fractures, the oldest were never reactivated. The youngest were most likely to be reactivated due to their orientation being closest to the modern-day SHmax. We also found that, controlling for other factors, natural and hydraulic fractures of were less common in rock that was more carbonate rich. Other variables such as mechanical stratigraphy and upward fracture growth play a significant role. Fractures have grown at least 70 feet upwards (and 15 feet horizontally) from the nearest hydraulically fractured well to the slant core. HFTS1 has the data to change the way the industry understands the fracturing process. Much of the data collected at the pad has now been released. This study places the unique HFTS1 slant core in a three-dimensional geomodel. We used this to place faults in the geomodel and to extract petrophysical information from the model at each fracture. This work brings together geologic, geophysical, and petrophysical data and statistics to improve our knowledge of the subsurface. These results are applicable for the Midland basin and for tight oil and geothermal projects around the world.