Earth Model Complexity and Risk Description in Resource Exploration and Development

William L. Abriel

William L. Abriel
Chevron Oil Company

Monday, April 26th, 2004 – 11:30 AM MST
Telus Convention Centre


SEG/AAPG 2004 Spring Distinguished Lecture

During the past 10 years, seismic imaging and analysis has expanded its role from structural exploration to reservoir description and property analysis. As experiences have developed, the description of the earth required to image and analyze the reservoirs has in many cases required significantly more complexity than anticipated. It is necessary to understand the range of earth complexity of the overburden to determine the accuracy of the seismic imaging, and the complexity of reservoir rocks to correctly risk quality and connectivity of flow compartments in oil and gas fields.

Seismic technology is a complex business. Historically, imaging and analysis tools have adopted or required simplifying assumptions in order to complete projects in a timely manner or simplify the descriptive analysis. Many of these assumptions are in widespread use today. Examples of this can be seen in seismic data processing applications that rely on a "flat earth" simplification, or reservoir analysis based solely on "bright spot" amplitude anomalies.

The difficulty facing earth scientists today is to understand, use and describe the right level of earth complexity for reservoir discovery and analysis. Using more complicated tools than necessary destroys project value by spending too much money and/or extending project time lines unnecessarily. However, using a tool that is too simple for a complex earth leads to a false sense of certainty and a commonly incorrect prediction (often wrong but never in doubt!).

In this talk, I'll review case histories of structural imaging, stratigraphic imaging, velocity complexity, and prediction of reservoir, pore pressure, and fluid flow from a mixture of geological environments around the world. I'll attempt to show the significance of earth complexity in the prediction analyses and the tools required handling it. Finally, I'll cover an overview of connecting the earth complexity to resource and risk prediction in resource exploration and development.


William Abriel (Bill) received his B.S. in earth science (1975) and his M.S. in Geophysics (1978) from the Pennsylvania State University. He joined Chevron oil Company in the fall of 1978 and worked for Chevron in New Orleans, Los Angeles, Perth Australia, and San Ramon California from 1978 to the present. During this time, he has been involved in many interesting projects in operations, seismic research and deployment. Bill was the first Chevron user or developer of the following technologies: 3D subsalt depth migration, 3D prestack depth migration, reservoir estimates from 3D seismic amplitudes, reservoir characterization from seismic data for reservoir simulation, 3D AVO, 3DDMO, dual sensor bottom cable acquisition, turning wave migration, and forming a team of geology, geophysics and reservoir engineering. During this time, Bill has worked on projects in areas including Gulf of Mexico offshore and onshore, North Atlantic (USA, Canada, UK, and Africa), West Australia, Brazil, China, and Saudi Arabia.

Bill is an active member of the SEG, EAEG and AAPG. He has served on the board of The Leading Edge, and as an associate editor of Geophysics. Bill also serves with the SEG Development Geophysics and Global Affairs committees, and is the current President of the Bay Area Geophysical Society. He has been a co-chair of technical meetings including the first SPE deepwater conference ('97), the Latin American Geophysical Convention (Caracas '98), and the Society of Brazilian Geophysics (Salvador '01). Bill's interests include the pleasures of life with his law professor wife, raising three children, and coaching lacrosse.