Pressure Transient Analysis in Fractured Horizontal Wells withThree-Dimensional Flow: Case Study

摘要

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