Energy in the Americas by Amelia M. Kiddle

Author:Amelia M. Kiddle [Kiddle, Amelia M.]
Language: eng
Format: epub
Tags: Petroleum industry and trade
ISBN: 9781552389423
Publisher: University of Calgary Press
Published: 2021-08-13T20:33:06+00:00

Three Dimensions

The move from two-dimensional (2D) to three-dimensional (3D) seismic technology was decisive confirmation of the revolutionary potential of digital technology in the oil business. The concept of 3D seismology had existed since the earliest days of geophysics. Geoscientists have always sought to visualize the subsurface in three dimensions, not two. All seismic surveys, when they produce a subsurface contour map, are conceived of in three dimensions. By the early 1970s, the arsenal of digital data recording and processing techniques had taken exploration to an unprecedented level of sophistication, but imaging was still 2D.

Exxon claims to have shot the first 3D seismic survey over the Friendswood field south of Houston in 1967. Esso Production Research presented the results at an SEG meeting in 1970.52 It was a presentation that displayed a model based on data gathered from well logs and 2D seismic surveys, and it used a special fibre optic viewer to simulate depth in three dimensions. Although Exxon later received the Distinguished Achievement Award from the SEG for “inventing” and developing 3D methods, this was not actually 3D technology as it came to be properly understood and practised. As GSI’s Robert Graebner put it, “3D involves gathering data in a spatial sense so that you can put together that data from wherever it reflected with another piece that came from that same spot.”53 This means doing 3D “migration.” Migration is the geometric repositioning of the return signal to show the exact subsurface location where the seismic wave reflects, as opposed to where it is picked up by the geophone. To position events accurately in three dimensions was a massive computational challenge. It required building a mathematical and physical model governed by the so-called wave equation, which is a hyperbolical partial differential equation that describes the propagation of waves.54 This is not what Exxon (Esso at the time) was doing in the Friendswood field in 1967.

The density of spatial seismic coverage required to produce a 3D image magnified the computational challenge of migration. A detailed 2D seismic survey might collect data in a grid spaced at one-kilometre intervals, whereas a 3D survey would require a much tighter grid, by at least an order of magnitude, to get any kind of accurate detail. By the early 1970s, computing power and digital seismic acquisition and processing techniques had developed to a point where this was finally possible. But, as with every major step forward with geophysical technology, the constraint on commercializing this concept was cost. And again, it was GSI that pioneered the technology and successfully marketed it to industry.

In early 1972, an important brainstorming session took place at GSI headquarters in Dallas. The principals were research scientist William Schneider, Milo Backus, then director of research, and Robert Graebner and M. E. “Shorty” Trostle, both executives. To fund an experimental survey to test the idea, the GSI executives enlisted the support of six large oil companies—Chevron, Amoco, Texaco, Mobil, Phillips, and Atlantic Richfield. They selected the Bell Lake field in southeastern New Mexico and West Texas, which was “a structural play with nine producers and several dry holes.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.