Imaging through gas clouds: A case history from the Gulf of Mexico

Abstract

Results from the worlds largest 3D four component OBC seismic survey will be presented. Located in the West Cameron area, offshore Gulf of Mexico, the survey operation totaled over 1000 square kilometers and covered more than 46 OCS blocks. The area contains numerous gas invaded zones and shallow gas anomalies that disturb the image on conventional 3D seismic, which only records compressional data. Converted shear wave data allows images to be obtained that are unobstructed by the gas and/or fluids. This reduces the risk for interpretation and subsequent appraisal and development drilling in complex areas which are clearly petroleum rich. In addition, rock properties can be uniquely determined from the compressional and shear data, allowing for improved reservoir characterization and lithologic prediction. Data acquisition and processing of multicomponent 3D datasets involves both similarities and differences when compared to conventional techniques. Processing for the compressional data is the same as for a conventional OBC survey, however, asymmetric raypaths for the converted waves and the resultant effects on fold-offset-azimuth distribution, binning and velocity determination require radically different processing methodologies. These issues together with methods for determining the optimal parameters of the Vp/Vs ratio (γ) will be discussed. Finally, images from both the compressional (P and Z components summed) and converted shear waves will be shown to illuminate details that were not present on previous 3D datasets.

Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

“…Imaging with multicomponent seismic data can better describe the physics of wave propagation, and resulting seismic images more accurately characterize the subsurface (Zhu et al, 1999;Gaiser et al, 2001;Simmons and Backus, 2003;Stewart et al, 2003;Ravasi and Curtis, 2013). Pure-mode (SS) or converted-mode (PS/SP) shear-wave images have many applications: For example, they provide useful information to discriminate gas-related from nonhydrocarbon-related reflection amplitude anomalies (Hughes et al, 2010), image through gas clouds where the P-wave signal is attenuated (Thomsen et al, 1997;Knapp et al, 2001), estimate density (Leiceaga et al, 2010), improve the ability to characterize lithology (Shahraeeni and Curtis, 2011;Shahraeeni et al, 2012), and detect fractures (Li, 1998).…”

Support of Gulf of Mexico Hydrate Research Consortium: Activities to Support Establishment of a Sea Floor Monitoring Station Project

“…While the design presented in this document could be implemented using a variety of conventional relational database management systems (RDBMS), future enhancements will benefit from a database management system with object relational support 25 .…”

“…How the event triggering will be realized has yet to be addressed. 25. In late January, Norm will be able to commit to some form of data structure.…”

Multicomponent seismic data registration for subsurface characterization in the shallow Gulf of Mexico

“…The data used in this study are from a multi-client 4-C ocean bottom cable survey acquired over 46 OCS blocks of East Cameron South, offshore Louisiana in 1999 and 2000, covering approximately 1000km 2 (Knapp et al, 2001). The survey is located on the continental shelf in water depths of approximately 100m.…”