Tightly spaced horizontal wells are widely used in the development of unconventional resources. The effectiveness of this strategy is largely affected by interwell fracturing interference indicated by interwell fracture geometry and frac hits, as interwell interference affects both parent and infill well productions. This work proposes a reservoir-geomechanics-fracturing modeling workflow for understanding the interference mechanism and quantifying effects of parent well fracture geometry, differential stress, and the design of infill well completion on interwell fracturing interference.
Reservoir models are constructed for the analysis of Eagle Ford scenarios. The numerical workflow involves a finite element model that fully couples reservoir flow and geomechanics and a complex multi-fracture propagation model coupling rock mechanics and fluid flow in wellbore and fractures. The workflow characterizes the temporal-spatial evolution of pressure and stress caused by legacy parent well production. The fracture model is employed to simulate the complex fracture geometry created by infill well completion based on updated heterogeneous reservoir stress state. The resulting fracture geometry quality is quantified by the occurrence of frac hits and the relative growth of fractures in longitudinal and transverse directions. Non-uniform fracture geometries lead to more complex stress change induced by depletion than uniform fracture geometries along parent wells. A smaller in-situ differential stress results in stronger stress reorientation caused by parent well depletion, which induces longitudinal fractures along infill wells and greatly reduces stimulated reservoir volume and initial well performance of infill wells. A larger in-situ differential stress induces less stress reorientation and is more likely to lead the fractures propagating toward pre-existing fractures, generate frac hits, and affect the production of parent wells. The quantification study in the sensitivity analysis indicates that differential stress and the infill well completion design have the most significant influences on interwell interference. This study suggests optimum infill well completion designs for Eagle Ford scenarios. The study also provides insights for infill well completion design in unconventional reservoirs developed by tightly spaced horizontal wells in terms of how to adjust field operational schedules to avoid frac hits and change the complexity of the interwell fracture networks.
