A new model for production analysis in naturally fractured shale gas reservoirs

Abstract

Based on the transient and linear flow behavior of shale gas production, a new model and its analytical solution were developed to predict the shale gas production in multi-stage fractured horizontal wells, in which the un-stimulated zone was considered as a dual porosity system. In order to validate the analytical solutions, numerical methods were also adopted, and good agreements between the two results were obtained. The characteristic gas rate curves were calculated using the new model, and sensitivity studies of various parameters were conducted based on dimensionless variables. The new characteristic curves were compared with the curves calculated using the SRV and Brohi's models. The results indicate that the new model can predict the flow regimes with linear flow and transition flow alternately, which are more complicated and realistic than that predicted using the Brohi model. The reservoir size, channelling coefficient and fracture permeability ratio all have significant effects on the characteristics of the gas production curves, while the effect of storativity ratio is not important because the porosity of the fractures is very low compared to that of the matrix. It may conclude that the un-stimulated region has an important contribution to gas production, which should not be neglected.