Отправлено: 15.12.11 04:52. Заголовок: Joint elastic-electrical effective medium models of reservoir sandstones

Geophysical Prospecting, 2011, 59, 777–786 doi: 10.1111/j.1365-2478.2011.00956.x
Joint elastic-electrical effective medium models of reservoir sandstones
Tongcheng Han1§, Angus I. Best1, Lucy M. MacGregor2, Jeremy Sothcott1
and Tim A. Minshull1

1National Oceanography Centre, Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH,
UK, and 2OHM Ltd, The Technology Centre Offshore Technology Park, Claymore Drive, Bridge of Don, Aberdeen, AB23 8GD, UK
Received July 2010, revision accepted February 2011
ABSTRACT
Improvements in the joint inversion of seismic and marine controlled source electromagnetic
data sets will require better constrained models of the joint elastic-electrical
properties of reservoir rocks. Various effective medium models were compared to a
novel laboratory data set of elastic velocity and electrical resistivity (obtained on 67
reservoir sandstone samples saturated with 35 g/l brine at a differential pressure of 8
MPa) with mixed results. Hence, we developed a new three-phase effective medium
model for sandstones with pore-filling clay minerals based on the combined selfconsistent
approximation and differential effective medium model. We found that
using a critical porosity of 0.5 and an aspect ratio of 1 for all three components,
the proposed model gave accurate model predictions of the observed magnitudes of
P-wave velocity and electrical resistivity and of the divergent trends of clean and
clay-rich sandstones at higher porosities. Using only a few well-constrained input
parameters, the new model offers a practical way to predict in situ porosity and clay
content in brine saturated sandstones from co-located P-wave velocity and electrical
resistivity data sets.
Key words: Clean and shaly reservoir sandstones, Effective medium models, Joint
elastic-electrical properties.