A New Exponential Productivity Equation for Low Permeability Gas Reservoirs Considering Starting Pressure Gradient

Based on the study of percolation mechanism of low permeability gas reservoirs and Rawlines and Schelldardt exponential productivity equation,the influence of starting pressure gradient was studied,a new productivity prediction formula and a new formation pressure calculation formula were derived.The analysis results of productivity data analysis indicated that as the starting pressure gradient G ps increased,the absolute open flowq aof of the gas well increased.At the same time,the formation pressure pand swept radius r were in S shape in the p-lgrcurve.As for the pressure gradient,the lower the starting pressure gradient G ps is,the faster it changes near the wellbore,the higher the G ps is,it changes relatively smooth near the wellbore,in the smaller area near the wellbore,the formation pressure gradient is almost equal to the starting pressure gradient.