Pressure transient analysis in fractured horizontal wells in unconventional reservoirs has received much attention in last two decades. A large number of microseismic data showed that many hydraulic fractures do not actually penetrate the entire formation, which means that 3D flow into the hydraulic fractures should be considered. However, there is limited work on analytical method based well-testing models for fractured horizontal wells with 3D flow. To improve this situation, a semi-analytical model for the horizontal well with partly-penetrated multi-state fractures are developed with considering 3D flow, based on fracture discretization. The new model proposed in this paper can describe more complex 3D flows in the multiple hydraulic fractures.
With flow regimes analysis and field application, it is found that the pressure derivative curves of fractured horizontal wells with 3D flow are complex. The most obvious feature of the flow regimes is that the curve appears to drop after the linear flow. It behaves like a second "hump" occurs in the pressure derivative curve. This is due to the fact that fractures do not penetrate the formation completely, and a pseudo-spherical flow occurs at this stage. The pseudo-spherical flow is more obvious when the fracture height is small or the fracture is short. Evaluated results from field application are basically consistent with the overall understanding of the MH shale oil reservoirs, which demonstrates the reliability and practicability of the proposed model. The evaluated fracture conductivity is less than an ideal value, because the fracture conductivity declines rapidly with the high reservoir pressure. This work helps to better understand the pressure transient behavior and to facilitate fracture evaluation in the unconventional reservoirs.