A new index used to characterize the near-wellbore fracture network in naturally fractured gas reservoirs

The effectiveness of the near-wellbore fracture network greatly affects the production potential of naturally fractured gas reservoirs. In this work, we develop an index to characterize the near-wellbore fracture network in naturally fractured gas reservoirs, which is defined as the fracture-network effectiveness index. To build such an index, multiple factors are considered, i.e., the fracture aperture distribution, the fracture porosity distribution, the fracture permeability distribution, and the fracture coverage ratio in the pay-zone. The new index has been calculated based on a variety of relevant field data which include well test analysis results, production test data, imaging logs, conventional logs, and three-dimensional (3D) whole-core computerized tomography (CT) scans. To validate this newly proposed index, the calculated index is applied to correlate with the absolute open flow capacity in a target formation located in the Xinchang gas field of China. Test results show that the natural fracture-network effectiveness index strongly correlates with the absolute open flow capacity in the selected wells. It indicates that the proposed index should be a useful tool for evaluating the production potential of the payzones in such naturally fractured gas reservoirs. This index can be also applied to guide the effective exploitation of naturally fractured gas reservoirs with multiple payzones.