JOINT INVERSION OF TRANSIENT PRESSURE AND DC RESISTIVITY MEASUREMENTS ACQUIRED WITH IN-SITU PERMANENT SENSORS: A NUMERICAL STUDY

Abstract

We develop a quantitative methodology to interpret jointly in‐situ transient‐pressure and dc resistivity measurements acquired in a hypothetical water injection experiment, with the goal of displacing oil in a hydrocarbon‐bearing formation. The assumed measurement acquisition system consists of enforcing time‐variable flow rates while injecting water into the surrounding rock formations, thereby producing a sequence of repeated transient‐pressure pulses. In‐situ dc resistivity measurements are acquired at the end of every flow‐rate pulsing sequence. The objective of the experiment is to estimate the spatial distributions of absolute fluid permeability and electrical resistivity. Geophysical inverse theory is used to account for the presence of noisy measurements. Synthetic data with noise are inverted to assess the relative benefits of different types of sensor geometries in axisymmetric models of permeability and electrical resistivity. Results strongly suggest that cooperative inversion of in‐situ transient‐pressure and dc resistivity measurements reduces nonuniqueness in the estimation of resistivity and absolute permeability governed by dynamic fluid‐flow phenomena. This leads to a more accurate estimate of permeability and resistivity compared to separate inversion of each data type.