Analytical Models for Predicting the Formation Resistivity Factor and Resistivity Index at Overburden Conditions (Meysam Nourani, Stratum Reservoir)

The presentation “Analytical Models for Predicting the Formation Resistivity Factor and Resistivity Index at Overburden Conditions” is given by Meysam Nourani, from Stratum Reservoir.


In this study, new parameters referred to as rock resistivity modulus (RRM) and true resistivity modulus (TRM) were defined. Analytical models were developed based on RRM, TRM and Archie’s equation for predicting Formation Resistivity Factor (FRF) and Resistivity Index (RI) under overburden pressure conditions. The results indicated that overburden FRF is dependent on FRF at initial pressure (ambient FRF), RRM and net confining pressure difference. RRM decreases with cementation factor and rock compressibility. The proposed FRF model was validated using 374 actual core data of 79 plug samples (31 sandstone and 48 carbonate plug samples) from three sandstone reservoirs and four carbonate reservoirs, measured under 4-6 different overburden pressures. The developed FRF model fitted the experimental data with average relative error of 2% and 3% for sandstone and carbonate samples respectively. Moreover, the applications and limitations of the models have been investigated and discussed. Further theoretical analysis showed that overburden RI is a function of RI at initial pressure, TRM and net confining pressure difference. The developed models supplement resistivity measurements and can be applied to estimate FRF, RI and saturation exponent (n) variations with overburden pressure.


Meysam Nourani is a SCAL project manager at Stratum Reservoir based in Stavanger, Norway. He has a background in chemical and petroleum/reservoir engineering, having held two postdoctoral researcher positions for total five years at Ugelstad laboratory in chemical engineering department of Norwegian University of Science and Technology (NTNU) and core analysis laboratory of Geological Survey of Denmark and Greenland (GEUS). He received his PhD in petroleum/reservoir engineering from Sharif University in 2010. His research interests include reservoir characterization and simulation, chemical EOR, laboratory core analysis, SCAL for CCS\CCUS and improved SCAL techniques and interpretation.