Dan Ebrom

The low-frequency gas shadow on seismic sections

About six years ago, Greg Partyka and his colleagues at Amoco Research showed how an old technique (the Fourier transform) could be used effectively for seismic interpretation and visualization. This idea has come to be known as spectral decomposition. In recent years, many spectral decomposition techniques have been developed and utilized for stratigraphic analysis and direct hydrocarbon detection. With the refined spectral decomposition techniques now available, the low-frequency shadow beneath gas reservoirs is another old idea that has renewed importance and interest in the exploration community. Almost a decade ago, Dan Ebrom studied a variety of possible mechanisms for the low-frequency shadow and why it might be associated with hydrocarbons. He presented his analysis at the 1996 SEG Summer Research Workshop.

4-C/4-D at Teal South

In late 1996, Texaco and Input/Output embarked on a novel experiment to test a low‐cost 4-C/4-D permanent reservoir monitoring system (PRMS). Western Geophysical and Digicourse were brought into the project to provide data acquisition and positioning services. In July and August 1997, four‐component (4-C) data acquisition was performed over 9 km2 in Eugene Island Block 354 (Teal South), using a dense shot grid (25×25 m). In late 1997, Texaco turned control of the project over to the Energy Research Clearing House and invited industry participation. The consortium remains open to new members.

Bin spacing in land 3-D seismic surveys and horizontal resolution in time slices

The cost of a land 3-D seismic survey is strongly influenced by the specified bin size. Halving the bin size will quadruple the number of stacked traces (assuming square bins), so there is considerable economic incentive to make the bins as large as possible. From an interpretive perspective, however, there are several disadvantages to 3-D data acquired with excessively large bin spacing. We investigate the constraints on bin size analytically, and then provide an experimental demonstration.

Subsalt pressure prediction from multicomponent seismics (and more

Predrill pore-pressure predictions are vitally important in deepwater arenas where extreme depth and drilling window conditions, typical of current prospects and developments, require expensive rigs and highly trained personnel to successfully plan and execute complex wellbores.

Pore pressure prediction using an Eaton's approach for PS‐waves

Mapping overpressure prior to drilling is critical for safe and successful hydrocarbon exploration (Caricone and Helle, 2002). Lack of predictability of abnormal pressures results in cautious drilling, and this leads to slow penetration rates, excessive bit wear and increased well cost and risk while drilling (Mukerji et al., 2002). The excess drilling cost in regions with abnormal pressure can amount to over

An Introduction to this Special Section: Development and Production

20 million per well (Mukerji et al., 2002) or

Sideswipe in a 3-D, 3-C model survey

1.08 billion per year worldwide (Dutta et al. 2002).

Integration—the watchword for pore-pressure studies

The 1999 SEG Development and Production Forum (11–16 July in Kananaskis, Canada) was intended to be a defining moment in the development of time-lapse measurements for use in reservoir management. As the meeting unfolded, it became clear that the intended defining moment had come and gone and a possibly more portentous, unintended moment was presaged by the meeting. What were these two moments?

AVO studies of gas sands via physical modeling

Development geophysics today is heavily dependent upon 3-D surface seismic acquisition. Why do 3-D? One reason, of course, is that a 3-D survey is commonly done at a tighter receiver spacing than most 2-D lines, thus allowing greater in‐line spatial resolution. But another reason is that, when energy returns from out of the source‐receiver plane, no 2-D data set can unambiguously identify this out‐of‐the‐plane intruder (sideswipe). In order to remove sideswipe from our 2-D lines, we must perform a 3-D migration. Simply put, 3-D problems require 3-D solutions.

Fracture dilatancy and seismic expression

Pore pressure remains a topic of fascination because it affects so many different aspects of oil and gas exploration and production. The implications of pore pressure and its sister technology, geomechanics, range from questions of maximum hydrocarbon column height (Can my structure meet my economics and not breach the seal?) to drillability (How many casing strings are needed to reach my objective?) to wellbore stability (What sorts of drilling cavings do I expect, and what do they mean?). Since the applications of pore-pressure estimation are as important to engineers as to geoscientists, a joint meeting was proposed, headed by SPE, with AAPG and SEG as cohosts. The meeting occurred in Galveston (at Moody Gardens) over 10–13 February, with the title “Integrating Stress and Pore Pressure Predictions for Exploration, Drilling, and Production.”