Pressure Transient Analysis for Hydraulically Fractured Wells with Changing Conductivity in Stratified Reservoirs: Case Study in Xinjiang Oilfield.

The oil development has been oriented toward deep-layer reservoirs and the commingling production and the separate-layer fracturing are important development methods. Currently, limited attention is given to the pressure transient analysis (PTA) of the fractured wells located in a stratified reservoir. Moreover, the proppant is very difficult to move inside the hydraulic fracture in the deep-layer reservoir, leading to the uneven fracture conductivity along the hydraulic fracture and increasing the complexity of PTA. To fill this gap, this work presented a fully analytical well test model for hydraulically fractured wells with changing fracture conductivity in stratified reservoirs, which is convenient to be used for interpreting the recorded pressure data from the oilfield due to its analytical nature. The establishment of this model is based on the trilinear flow model, Duhamel theorem, and pressure superposition principle. A systematic verification is conducted to ensure the validity of the proposed model. Furthermore, we offer a sensitivity analysis to investigate the effect of crucial parameters on pressure and pressure derivative, including the fracture extension, fracture conductivity, transmissibility factor, and storativity factor. Finally, a field case of a four-layer fractured well from Xinjiang Oilfield in Junggar Basin is interpreted to demonstrate the practicability of the presented model.