Estimation of in-situ petrophysical properties from wireline formation tester and induction logging measurements:A joint inversion approach

摘要

We introduce a novel inversion algorithm for the in-situ petrophysical evaluation of hydrocarbon-bearing formations.The algorithm simultaneously honors a set of multi-physics data:(a)Pressure-transient,flowline fractional flow,and salt production rate measurements as a function of time acquired with a wireline-conveyed,dual-packer formation tester,and(b)borehole array induction measurements.Both time evolution and spatial distribution of fluid saturation and salt concentration in the near-borehole region are constrained by the physics of mud-filtrate invasion.The inverse problem consists of the simultaneous estimation of the near-borehole permeability and parametric saturation functions of relative permeability and capillary pressure.A two-dimensional axisymmetric petrophysical model is assumed for the near-borehole region.Both horizontal and vertical permeabilities are subject to inversion.Saturation functions of relative permeability and capillary pressure are parametrically represented using a modified Brooks-Corey model.We simulate the response of borehole logging instruments by reproducing the multi-phase,multi-component flow that takes place during mud-filtrate invasion and formation test.A fully implicit finite-difference black-oil reservoir simulator with brine tracking extension is used to simulate fluid-flow phenomena.Induction measurements are coupled to the physics of fluid flow using a rapid integro-differential algorithm.Inversion experiments consider both noise-free and noise-contaminated synthetic data.Joint inversion results provide a quantitative proof-of-concept for the simultaneous estimation of transversely anisotropic spatial distributions of permeability and saturation-dependent functions.The stability and reliability of the inversions are conditioned by the accuracy of the a priori information about the formation porosity and fluid PVT properties.We develop an alternative sequential inversion technique for cases where multi-physics measurements lack the degrees of freedom necessary to accurately estimate all the petrophysical model parameters.The first step involves estimation of horizontal and vertical permeabilities from late-time transient-pressure measurements.Subsequently,the entire set of measurements is jointly inverted to yield saturation-dependent functions.