Paul Krail

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Paul Krail
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The Honors and Awards Committee recommended Paul Krail and Dwight Sukup for the Reginald Fessenden Award because of their pioneering work that showed the need for multi-azimuth acquisition in subsalt imaging. Their joint work at Texaco beginning in the 1980s included development of instrumentation to acquire multi-azimuth data and application of wave-equation imaging techniques to the resulting data for imaging beneath salt. Through modeling of synthetic data and actual fi eld results, they clearly demonstrated that superior images were obtained from using multi-azimuth data in 3D prestack depth migration.

Biography Citation for the Reginald Fessenden Award

Contributed Roberth H. Tathum

The Reginald Fessenden Award is certainly appropriate recognition of Paul Krail’s and Dwight Sukup’s contributions to the evolution of true 3D, or wide-azimuth, seismic technology. Their work has resulted in improved seismic imaging beneath salt canopies and in complex structural settings. Perhaps the most signifi cant aspect of this technological success, however, is the collaboration between Paul, Dwight, and others, with truly complementary areas of expertise: Paul Krail in acquisition, with experience as a party chief on early 3D (land) crews, designer of marine vessels and, significantly, offset VSP surveys; and Dwight Sukup, with a background as an applied mathematician developing and implementing flexible prestack depth migration schemes and algorithms compatible with varied geometrical complexities, including VSP and, ultimately, vertical cable technology.

The concept of the vertical cable evolved from a 1980’s Texaco task force to address seismic imaging beneath salt, especially in deep water. Recognition of offset VSP geometries with offset sources at all azimuths led to the suggestion of a “VSP without the borehole.” Team members were familiar with marine instrument manufacturers who constructed anchored vertical hydrophone arrays for anti-submarine warfare applications. Modifi cation of this technology to the seismic imaging application, including the cable with a hydrophone array suitable for seismic refl ection imaging and a recording buoy mechanically decoupled from the cable and capable of the recording and storage requirements for seismic surveys, was a straightforward development.

The ultimate application of the vertical cable requires several cables anchored to the sea fl oor and a small source vessel shooting a dense array of source positions over a wide surface area. Migration was applied to each cable position— implementing reciprocity and mirror migration of the surface multiple—using a single shot and wide areal (and azimuthal) distribution of receiver positions. Hence, the term “true 3D” as opposed to the single azimuth of offset information in a conventional towed-streamer survey.

The applications of the vertical cable are as fascinating as the evolution of the concept. The proof of concept using a single vertical cable in 1987 was at the Ewing Bank, followed by the fi rst actual application, with three cables, over the Tick prospect. In 1992, six cables were deployed in a 3D survey of the Gemini prospect, providing subsalt images that justifi ed drilling the discovery well in 1996. In 1995, a relatively dense survey over Strathspey Field in the North Sea addressed the objective of detailed structural imaging of small fault blocks. The true 3D vertical cable data images were indeed superior to the towedstreamer data and played a deciding role in future drilling decisions. About the same time, Shell and PGS acquired one of the fi rst wide-streamer surveys over Brent Field. In 1997, Statoil conducted a large four-component oceanbottom seismometer (OBS) survey over Stratfjord Field.

The OBS geometry provides similar “true 3D” geometry. Comparison of these three essentially contiguous surveys provides an interesting evaluation of the success of wideazimuthal acquisition. Later vertical cable surveys include Fuji in 1995, Fuji II in 1998, and a west of Shetlands subbasalt survey in 1997.

Many of the “true 3D” and wide-azimuth aspects of vertical cable technology are also realized with fourcomponent sea-fl oor (OBS) recording, including Krail’s and

Sukup’s involvement in the Teal South and Donald surveys in the Gulf of Mexico. The foresight and collaboration of Paul Krail and Dwight Sukup have signifi cantly contributed to the continued creative insights for all those working on improving seismic imaging by implementing wide-azimuth 3D techniques in the diffi cult geologic settings where future energy resources may reside.