Fracturing in Tight Gas Reservoirs:Application of SCAL Methods to Investigate Formation Damage Mechanisms

摘要

Gas well productivity in tight reservoirs is greatly impeded by the fracturing fluid interactions with the formation.New simulators introduce formation damage mechanisms to calculate gas well productivity.However,equations describing formation damage must be supported by experimental data obtained in conditions representative of fracturing operations.The purpose of this work is to derive the absolute permeability damage and multiphase flow upon return gas permeability after core invasion by a fracturing fluid by methods used in Special Core Analysis Laboratory (SCAL).The core permeability is in the microDarcy range.Experimental data of absolute permeability damage due to the fracturing fluid filtration and water sensitivity of this illitic sandstone as well as water saturation profiles measured by X-Ray in two phase flow experiments are interpreted.The methodology of interpretation provides the petrophysical data specific to the rock-fluid system:the absolute permeability,the relative permeability damage due to hysteresis,and the capillary pressure curve.In addition,simulations are presented for the evaluation of the impact of various operational parameters like pressure draw-down on the gas productivity.It is shown that permeability hysteresis must be considered to explain the low gas recoveries at short term.On the long term,the natural clean-up is very slow.The results,derived from a real rock-fluid system,are used to provide recommendations for improving back flow procedures.This methodology can be applied to any case of damage due to the alteration of rock-fluid properties.