Articles

Seismic Data Acquisition Developments in the Last Decade and in the Next – A Biased View

Gijs Vermeer

Almost simultaneously with the invitation to contribute to this special issue of the Recorder, the January-February 2001 issue of Geophysics happened to arrive. The latter contains a special section: “Geophysics in the new millennium”, put together under the direction of Larry Lines (2001), whose name also featured under the letter…

AVO Analysis

John P. Castagna

The great promise of pre-stack amplitude-versus-offset analysis (AVO) of reflected compressional waves lies in the dependence of the reflectivity with increasing offset on the elastic property contrasts at the reflecting interface. As different lithologies may exhibit distinct Poisson’s ratios, and gas-bearing strata usually exhibit anomalously low Poisson’s ratios, AVO has…

AVO: Yesterday, today, and (a peek at) tomorrow

Mike Graul

Amplitude variations with offset (AVO) have been used for over a quarter of a century in the hunt for gas and oil. The first public disclosure of the technique was made by Bill Ostrander, at the 1982 SEG convention in Dallas. At the time, Bill was reporting on a seasoned…

AVO and Lamé Constants for Rock Parameterization and Fluid Detection

Bill Goodway

For more than 3 decades, industry has known that shear seismic waves (S-waves) contain different rock information than do our standard compressional seismic waves (P-waves). Periodically, efforts to record S-waves, even on the seabed, have attracted industry attention with increasing success. Separate efforts to analyse conventional P-waves for the S-wave…

AVO Feasibility and Reliability Analysis in the Presence of Random Noise

Jon Downton and Larry Lines

AVO inversion provides a cost effective means for predicting elastic parameters and rock properties of the earth. However, the results of AVO inversion are sensitive to noise. For some acquisition, geometries and noise levels predictions from the AVO inversion may not be reliable. By studying the influence of random noise…

AVO and the General Inverse Theory

Guillaume Cambois

The 1980s saw the development of two new technologies: AVO and general inverse theory. In those days, general inverse theory was applied to full waveform inversion, compared to which AVO is a very simple problem. Almost two decades later we observe that the interest for full waveform inversion has waned,…

Prestack Waveform Inversion Using a Genetic Algorithm – The Present and the Future

Subhashis Mallick

Use of prestack data for quantitative analysis of hydrocarbon reservoirs has gained popularity over the past decades. Most of these quantitative studies rely on the seismic reflection amplitude variation with offset or AVO analysis. AVO makes a simple assumption that every reflection event on the prestack seismic data is a…

Natural Gas Hydrate Studies in Canada

R.D. Hyndman and S.R. Dallimore

Scientific field studies of natural gas hydrates have been carried out in Canada for many years by the Geological Survey of Canada and by a number of universities. This article describes the two largest programs: (1) Arctic permafrost-related hydrate studies, including the Mallik research drilling on the Mackenzie Delta and,…

Vibroseis Deconvolution: An Example from Pikes Peak, Saskatchewan

Katherine Brittle and Larry Lines

Vibroseis has enjoyed worldwide popularity in land seismic acquisition ever since its development by Conoco’s researchers (Crawford et al., 1960). Crosscorrelation of the sweep with the recorded data, which emulates the methods developed in chirp radars by Klauder et al. (1960), will ideally produce zero-phase wavelets with a flat spectrum.…

The Application of AVO and Inversion to the Estimation of Rock Properties

David Gray and Eric Andersen

Inversion of Amplitude versus Offset (AVO) results can be used to derive elastic rock properties, which can in turn be used for quick determination of lithology and fluid content of reservoirs. In this paper, this approach is illustrated using case histories from a Western Canadian gas-field development, exploration in the…

Rock Physics for the Rest of Us – An Informal Discussion

Jan Dewar

Rock Physics describes a reservoir rock by physical properties such as porosity, rigidity, compressibility; properties that will affect how seismic waves physically travel through the rocks. The Rock Physicist seeks to establish relations between these material properties and the observed seismic response, and to develop a predictive theory so that…

International Geophysicists in Canada

Gordon Cope

With the rapid expansion of the Canadian oilpatch into international waters over the last decade, many native-born geophysicists have had the opportunity to travel and work around the world. Just as importantly, geophysicists from all points of the globe have had the chance to come to Calgary and practice their…

Aliasing for the Layperson

Larry Lines, Katherine Brittle, Ian Watson, and Peter Cary

Examples of aliasing can be observed in western movies by watching the motion of stagecoach wheels. As the stagecoach starts to move, we observe its wheels rotating in the expected forward direction. As the stagecoach speeds up, we see that the wheels appear to rotate in the opposite direction to…

3D Model Evaluation by Data Simulation

Norm Cooper and Michael Cooper

A Master License Agreement

G. Fairs, J. Boyd, P. Einarsson, L. Hunt, B. Korchinski, L. Ramescu, C. Walls, B.L. Parlee

For decades the licensing of seismic data was based mostly upon a handshake and an understanding of common industry practice. Over time common industry practice as it relates to the use of licensed seismic data has become quite diverse, even to the point where it could be said that there…

Wembley Halfway B Pool – A Test Case for 3D Visualization Technology

Ronald C. Hinds and Hugh Lavallee

The Wembley Halfway B Pool is situated 20 km northwest of Grande Prairie, Alberta and was discovered in 1978. This Middle Triassic pool contains an oil leg with 23 x 106m3 inplace (145 MM barrels-in-place) and an associated gas cap with 5.7 x 109m3 in-place (204 bcf-in-place). The Halfway B…

Beam Steering and Controlled Illumination

George Adler

Beam steering and controlled illumination are closely related in geophysical processing. The idea of beam steering has been used in physics for a long time. For example, in radar technology it is possible to steer the radar wave without moving the antenna itself, by applying proper phase shifts between radiating…

Seismic Deconvolution: Assumptions, Concerns and Convictions

Peter Cary

Early in our careers as geophysicists, most of us took at least one course on seismic signal analysis where we were taught that standard Wiener deconvolution converts the minimum-phase source wavelet in our seismic data to a wavelet with a phase spectrum that is zero and an amplitude spectrum that…

AVO Processing: Myths and Reality

Guillaume Cambois

AVO processing is meant to make the input data compatible with Shuey’s equation. This task is extremely difficult due to the overly simplistic formulation of the problem compared with the complexity of the real physical experiment. Fortunately, the advent of elastic impedance has made it possible to relax some of…

Imaging Through Gas Clouds: A Case History in the Gulf of Mexico?

S. Knapp, N. Payne and T. Johns

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…