Gas-hydrate concentration and uncertainty estimation from electrical resistivity logs: examples from Green Canyon, Gulf of Mexico

Authors: Sava, D.C., and Hardage, B.A., Bureau of Economic Geology, University of Texas, Austin, TX.

Venue: Society of Exploration Geophysicists’ 77th Annual Meeting in San Antonio, TX, September 23-28, 2007 (http://meeting.seg.org/ [external site]).

Abstract: Many gas-hydrate systems from deepwater, near-seafloor strata in the Gulf of Mexico have limited availability of data because the targeted logging intervals from these regions are deep reservoirs. The usual well-log information acquired over the gas-hydrate stability zone is restricted to gamma-ray and resistivity logs. In addition, sparse geotechnical data are available. Therefore, in estimating gas-hydrate concentration in these environments, researchers should take into account the inherent uncertainty associated with their predictions. In this paper, the authors present a methodology for estimating gas-hydrate concentration and its associated uncertainty using resistivity logs. Their methodology combines rock-physics theories and empirical relations with stochastic simulations. They also present a technique that helps calibrate Archie’s Equation (1942) for estimating gas-hydrate concentration, based on resistivity logs using the theoretical Hashin-Shtrikman (1962) Lower Bound on electrical resistivity. This method is especially useful when there is limited availability of resistivity and porosity data for calibrating the empirical parameters in Archie’s Equation. The authors also show examples of estimating gas-hydrate concentration and the associated uncertainty for well-data from the Green Canyon area of the Gulf of Mexico. Click here for the full paper.

Related NETL Project: The proposed research of the related NETL project DE-FC26-06NT42667, “Combining Multicomponent Seismic Attributes, New Rock Physics Models, and In Situ Data to Estimate Gas-Hydrate Concentrations in Deepwater, Near-Seafloor Strata of the Gulf of Mexico,” is to develop a methodology to improve our ability to accurately estimate the concentration of gas hydrate in deepwater, near-seafloor strata and enhance our understanding of the relationships between seafloor stability and the free-gas-to-hydrate transitions that occur in marine hydrate systems.

NETL Project Contacts
NETL – Frances Toro (frances.toro@netl.doe.gov or 304-285-4107)
UT/BEG – Dr. Bob Hardage, UT Austin (bob.hardage@beg.utexas.edu or 512-471-0300)