Productivity model for fractured horizontal wells in tight gas reservoirs considering secondary fractures and water-blocking damage

It's common to use multi-stage hydraulic fracturing in horizontal wells for the development of tight gas reservoirs. Therefore, accurate productivity prediction is crucial. Concerning the theory of equivalent wellbore radius and the principle of pressure drop superposition, the effects of secondary fractures and water-blocking damage were treated as distinct skin effects innovatively. Consequently, the productivity model for tight gas reservoirs in hydraulic fracturing horizontal wells was established, taking into account the effects of slippage effect, stress sensitivity, threshold pressure gradient and high-velocity non-Darcy flow. Then the accuracy of the model was verified in two ways. The calculated results are basically consistent with different models from the literature without considering the influence of various factors. In addition, the open flow capability of the proposed model by using the data of a gas field block is 1617.85Mscfd, while that of one fractured well through field well testing is 1696.79Mscfd, resulting in a relative error of 4.65%. Furthermore, the factors affecting productivity were subjected to a sensitivity analysis using this model. The results indicate that water-blocking damage can significantly impact productivity, while threshold pressure gradient, fracture number, and high-velocity non-Darcy flow have a relatively small influence on productivity.