Estimating the Fracturing Fluid Recovery in Shale Gas Reservoirs: Experiments and Field Data Analysis

摘要

In shale gas reservoirs, the fluid flowback rates have become one of the key parameters to evaluate the fracturing operation and manage fracturing fluid after well stimulation. Based on experimental tests and a field data analysis, this paper proposed a method to estimate the fracturing fluid recovery. First, fracturing fluid imbibition and flowback experiments were conducted with fractured and matrix downhole shale plugs, and the average flowback rates for matrix and fractured samples were tested. Then, using a material balance model, the percentages of fluid retained in matrix and fractures are determined with the earlystage well production data. Combining the experimental and field results, a linear superposed model was adopted to compute the final fracturing fluid recovery. The values for the selected two wells were 23.3% and 26.2%, respectively, slightly smaller than the field-recorded values, which may be attributed to the underestimation of the flowback rate in fracture networks. A sensitivity analysis demonstrated that the recovery was more sensitive to the fluid flowback rate in fractures as more than a half of the fracturing fluid stayed there. The outcomes of this paper may explain the reasons why the fracturing fluid recovery of shale gas wells fluctuates in a wide range and wells with low flowback rates usually have a high productivity.