Flowback Fracture Closure of Multifractured Horizontal Wells in Shale Gas Reservoirs

摘要

In multi-fractured horizontal wells(MFHW),fracture properties such as permeability and fracture halflength significantly deteriorate during early production,which negatively affects gas production from shale reservoirs.Therefore,it is crucial to evaluate the temporal changes in fracture properties based on production data.This paper presents a workflow in which both flowback and long-term production data are used to quantitatively evaluate hydraulic fracture closure and changes in the fracture properties.In addition,we develop a two-phase semi-analytical model based on rate transient analysis(RTA)that assumes boundary dominated flow during the flowback period.The proposed workflow consists of three steps.First,we used the flowback data to calculate fracture properties,such as initial fracture permeability and fracture half-length,by employing the two-phase semi-analytical model.Then,we calculated initial fracture permeability by using a single-phase bilinear flow model as well as the fracture half-length and matrix permeability by using a single-phase linear flow model from the long-term gas production data.These models consider pressure dependency of permeability.Last,we compared the results that are calculated from both flowback and long-term production data to evaluate fracture closure and its effects on fracture permeability.We validated the semi-analytical flowback model and the workflow against numerical simulations.The results show that the developed model is capable of predicting fracture properties and evaluating fracture closure.Furthermore,the proposed workflow provides quantitative insights on the performance of fracture stimulation and is able to closely estimate permeability modulus using flowback and long-term production data instead of conducting laboratory experiments.