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Consistent joint elastic‐electrical differential effective‐medium modelling of compacting reservoir sandstones
Author(s) -
Jensen Erling Hugo,
Gelius LeivJ.,
Johansen Tor Arne,
Wang Zhong
Publication year - 2013
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12014
Subject(s) - geology , reservoir modeling , shearing (physics) , compaction , joint (building) , porosity , mineralogy , geotechnical engineering , architectural engineering , engineering
Improved reservoir characterization and monitoring can be achieved by combining seismic and controlled‐source electromagnetic techniques. This requires developing coherent rock physics descriptions. In this paper we demonstrate consistent joint elastic‐electrical modelling according to the differential effective‐medium theory. We test our modelling against data from a compaction experiment on a set of 11 sandstone core samples from the same quarry location. The presented approach is analogous to calibrating a rock physics model to a particular reservoir based on data from possible well logs and core samples. For simplicity we choose to use multivariable non‐linear regression in the inversion. It shows that this technique is able to identify solutions that are physically sound. However, a more rigorous inversion method might be considered in future implementations. To identify the critical parameters we test the elastic‐electrical sensitivity of the various unknown variables involved. The most sensitive parameters identified are then perturbed during the modelling. The mineralogy consists mainly of quartz, which we assume to be spherical and kaolinite. We use the resistivity to calibrate the aspect ratio of the clay grains and estimate the porosity reduction due to compaction. These values are in turn used in inverse modelling of the bulk and shear moduli. The solid minerals make up the inclusion material in the differential effective‐ medium modelling for both the elastic and electrical properties. Hence, this formulation constitutes a consistent joint elastic‐electrical modelling scheme. We achieve good fits between the model results and the laboratory measurements for most of the samples. The reason for the less good fit with some of the samples might be due to measurement errors in the laboratory. This is supported by the observed abnormal stiffness compaction trends associated with those samples.