Reservoir Evaluation from an Automatic Saturation Inversion Algorithm Using TLIL Data

Invasion of drilling mud filtrate into a reservoir is related to time after the bed was reached, so that logging-tool response is a function as time. Traditional algorithms of resistivity inversion are based on a simplified step-invasion model that is independent on time, hence it is difficult to obtain the dynamical image of a realistic invasion process and the accuracy of inversion is affected. An automatic inversion algorithm of time-lapse induction log (TLIL) is modeled with fluid-and formation-related parameters that control the dynamic invasion process. It is able to characterize the dynamic invasion process realistically and to provide more information for log analysts to evaluate reservoirs. From matching simulation results with time dependent field logging data, the present model can yield more reliable estimates of formation properties such as radial heterogeneities resulting from invasion, original fluid parameters, etc. Field applications for dual-induction measurement illustrate that the method is reasonable and efficient for evaluation of reservoirs.