Research on hydraulic fracture propagation and interwell interference mechanisms during multi-well pad fracturing in shale reservoirs

Abstract

Shale reservoirs have unfavourable characteristics such as strong heterogeneity and vertical multiple layers. Multi-well pad fracturing is a highly efficient fracturing technology that can achieve stereoscopic reservoir exploitation. Previous studies usually focused on 2D models, but they cannot simultaneously achieve longitudinal and vertical propagation. Through continuum-discontinuum element method (CDEM), a CDEM-HM3D model is established to investigate the fracture propagation mechanism under well interference and the influences of well spacing, well layout, and fracture spacing on multi-well pad fracturing in a field-scale shale reservoir model with bedding planes. Results show the fracturing performance from preferential fracturing in the lower-stress layer is superior to that in the high-stress layer. The former fully utilizes interwell interference to avoid fracture penetration in the high-stress layer, which is conducive to the safe and independent development of the target reservoir. Compared with staggered well fracturing, stacked well fracturing can more effectively compensate for the reconstruction difference between different layers and activate more bedding area, but the fracture control range decreases. Under the premise of no fracture penetration, increasing the well spacing properly can expand the fracture control range and achieve optimal fracturing performance. An optimal fracture spacing can prevent fracture penetration in the high-stress layer and enlarge the transverse fracture control range, thereby exploiting more resources between fractures. The results can provide theoretical guidance for the efficient development of shale reservoirs.