Journal of Canadian Petroleum Technology, Vol.45, No.10, 18-20, 2006
Rate dependence of transient linear flow in tight gas wells
Many tight gas wells,(permeability less than 0.1 mD) exhibit transient linear flow; sometimes for several years. This behaviour differs from radial flow in many ways. This paper reports another import difference between linear flow and radial flow-rate sensitivity. It has been shown and accepted for years that real gas pseudo-pressure can be used to apply analytical solutions to transient radial flow. However, it has been noticed that analytical solutions can be in serious error when applied to transient linear flow. Specifically, the slope of the root t plot departs from the analytical value as the flow rates or degree of drawdown becomes higher. This paper demonstrates the rate/drawdown sensitivity of transient linear flow. Then a correction factor is presented which corrects the slope of the plot and improves the accuracy of root k A(c) and OGIP, as calculated from production/pressure performance.