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Properties of High-Pressure Gas Flows Near a Wellbore in a Fractured Well During Well Test

Abstract

In petroleum production, porous media flow of the reservoir fluid in the near wellbore region plays an important role in determining the production rate and the mechanical integrity of the wellbore. A major portion of the pore pressure drop occurs within a short distance from the wellbore. The large drop in gas pressure over a short distance can cause gas inertia effect to be significant. The purpose of this paper is to present the identify condition under which gas inertia effect needs to be considered in the gas pressure profile and mass flux. When the gas inertia effect is appreciable, it is responsible for changes of gas mass flux and pressure distribution. Analytic model presented in this paper is based on a high pressure gas radial flow in homogeneous porous media. The momentum equation consists of inertia effect and quadratic Forchheimer term. With the application of non-dimensional analysis, the governing equations for steady radial flows in a polar coordinate under isothermal condition are given. Pressure distribution and mass flux are investigated by the non-dimensionless equations. It has been shown that the inertia and Forchheimer term in the equation of motion have the same effects which reduce mass flux and steepen pressure curve near a wellbore. The identify condition under which gas inertia effect needs to be considered in the gas pressure profile and mass flux is determined by the dimensionless parameter which consists of wellbore radius, Forchheimer coefficient and porosity. The identify condition is different from that proposed by others. Analytical results show that the identify condition is reasonable. This work will be of significantly importance to engineers during designing test difference pressure, understanding the pore pressure distribution for well testing, and predicting productivity of high gases. Another interesting possible application would be in the study of gas outbursts in coal mines.