Pressure transient behavior modeling of a multi-horizontal well pad with damaged fracture in shale gas

Multi-fractured horizontal wells significantly promoted the development of shale gas, and multi-well pads are applied generally in field application. The interference between adjacent wells attributed to the close well spacing becomes an issue that must be considered. Also, with the proppant accumulation in near-wellbore, fracture damage with low permeability and strong stress sensitivity usually occurs in far from wellbore fracture section. A semi-analytical model of multi-horizontal well pad with damaged fractures is established for the first time with a method that can deal with non-uniform fractures. Based on numerical inversion, the type curve is obtained and eight regimes are identified by the characteristics of the pressure derivative curve. Good agreement with the numerical simulation manifests the correctness of our model. Afterward, the influences of crucial parameters on pressure transient are studied. Considering the influence of adjacent wells, the pressure derivative curve elevates since well interference regime and finally maintains at a value of n-ary sumation 0.5qwDi during whole system radial flow. Well spacing has an impact on the appearance time of the well interference regime. The pressure transient type curve since well interference regime moves up with higher production rate of adjacent wells. The damaged fracture section influences the early time pressure transient. With the increase of damaged fracture length, the early time pressure drop is enhanced. With consideration of stress sensitivity, 'hump' would be identified in the pressure derivative curve. Compared with undamaged fracture section, the 'hump' caused by the stress-sensitive damaged fracture section appears earlier due to a sharper conductivity decline. The model reveals the flow mechanism of stress-sensitive partially propped fractures and provides some new insights on pressure transient analysis of multi-horizontal well pad in shale gas.