ADVANTAGES IN JOINT-INVERSIONS OF RESISTIVITY AND FORMATION-TESTER MEASUREMENTS: EXAMPLES FROM A NORWEGIAN FIELD

摘要

Past studies have reported the strong benefits from the joint-integration of resistivity and formation-tester measurements in conventional petrophysical evaluation. However, the practical aspects of such integration are still unclear for many experienced log analysts. This paper illustrates the successful application of this multiphysics approach by using data acquired in a Norwegian field. Unlike previous approaches, we use a reservoir simulator dynamically-coupled to a mud-filtrate invasion model to enforce two-phase fluid flow in a multilayered rock formation model. The simulated resistivity and formation-tester measurements explicitly take into account specific two-phase flow and mudfiltrate invasion properties, such as capillary pressure and relative permeability. The integration of resistivity and formation-tester measurements involves an iterative process with the following steps: 1) Simulation of mudfiltrate invasion and resistivity tool responses based on an initial multilayered rock formation model. 2) Update the rock formation model by using pressure transient data. 3) Iterate between 1) and 2) until a match is obtained with both pressure transient measurements and resistivity measurements. The formation tester measurements were acquired with a dual-packer module and resistivity measurements were acquired with laterolog tools. Generally, the examples from different wells shown in this work exhibited promising results into constraining the multiple solutions inherent to multilayered rock formation models. The nuclear magnetic resonance (NMR) log was applied to divide the formation into different layers by ordering the T2-distributions into a limited number of electrofacies. In another well, where NMR data was not available, we suggest that a permeability correlation formula derived from core data be used instead. Several sensitivity studies were performed on the final inverted values in an effort to quantify the level of uncertainty present in the estimation process. The final result is a constrained multilayered rock formation model where the complexities of multiphase flow have been taken into account, which is more representative of the existing rock formation than models obtained through standalone well-log correlations.