Speaker Abstracts
November, 2007
Prestack 9-C Joint Inversion for Stratigraphic Prediction in the Williston Basin
Bryan DeVault, Vecta Oil and Gas
Thierry Tonellot, Danièle Macé, Stéphan Ker, Morgane Pichard, IFP
Abstract
We have successfully applied the multicomponent prestack elastic waveform inversion methodology proposed by Agullo et al (2004) to 9-C 3D data from North Dakota. The objective of the survey was to image grainstone shoals which form subtle stratigraphic traps for oil using the P and shear modes. The shoals are a difficult exploration target as they are characterized by a subtle, nonunique P-wave seismic response, but are prolific when encountered, with typical well recoveries of nearly 150 MBO and some wells producing in excess of 500 MBO. Prestack joint elastic inversion of the P and SH modes delineates both the shoal itself and the updip seal facies that act as the trap in this part of the play. The prestack inversion process comprises 3 steps: separate inversion of the P and SH data, a registration step which matches the P and SH impedances and outputs a P-SH time rule, and the joint inversion using the P and SH angle stacks, a background impedance model, and the P-SH time rule. Outputs are P and S impedance and density, in P-wave time. Elastic attributes were particularly useful in characterizing the dolomite fraction at the reservoir, which allowed mapping of trap geometries. Incorporation of the shear data and use of a newly-developed warping procedure for the registration resulted in great improvements over prestack P-wave inversion.
Bio
Bryan DeVault received a B.S. in mathematics and physics from the University of Houston in 1990 and a Ph.D. in geophysics from the Colorado School of Mines in 1998. After school he became an international expat for Shell International Exploration and Production in the Netherlands, where he worked until 2001, after which he joined Anadarko Petroleum in Houston. At Anadarko he was able to participate in several successful lease sales leading to major discoveries in the Deepwater Gulf of Mexico. He joined Vecta in 2003, becoming President in 2006. Professional interests include multicomponent seismic, AVO analysis, seismic inversion, and the application of stratigraphic concepts to exploration and production. He is a member of AAPG and SEG.
