Abstract: The inflow performance relationships (IPR) with starting pressure gradient are presented based on Wiggins' Darcy flow work, which supports application of IPR analytical technique in low and extremely low permeability reservoirs. In this paper, sensibility analysis for affecting major inflow-performance factors is made, showing that IPR with starting pressure and its process differ significantly from those of using Darcy flow. It is demonstrated that production of low permeability reservoir is theoretically based on the process of big pressure difference and close spacing in general. According to the new equations proposed here, the well performance characteristics of Chang -6 extra-low permeability reservoir in Jing'an oilfield are analyzed, proving its better predictions of such a reservoir productivity than present conventional methods.

Key words: IPR curve, starting pressure, low permeability reservoir, productivity evaluation