SEMINAR - John Warme

Interpretation and Significance of Cretaceous and Eocene Coastal Outcrops, San Diego County

John E. Warme
Professor Emeritus, Colorado School of Mines, Golden, Colorado

April 16th, 2008

The Upper Cretaceous and Eocene formations that crop out along seacliffs and landward in San Diego County have been studied and reinterpreted several times over the last century. By the 1970's they were regarded as prime examples of lateral facies relationships from continental to deep marine, then reinterpreted as pioneering examples of sedimentary intervals separated by significant surfaces that formed discrete unconformity-bounded intervals, or sequences, of the evolving concept of Sequence Stratigraphy.

Cretaceous examples include the Point Loma thin bedded turbidites and mudstones and overlying Cabrillo Formation conglomerates that are still validly argued as genetically-related lateral facies, or conversely, completely separate sequences; these units require more analyses.

In contrast, the uppermost lower Eocene to upper Eocene series exhibit superb examples where unconformity surfaces that separate genetically unrelated intervals define stratigraphic "Sequences". However, such surfaces do not in every case follow the prior definitions of formation boundaries. One of several examples is the unconformity the cuts across the shallow-water to intertidal beds of the Delmar Formation and Torrey Sandstone and is overlain by a sandy and conglomeratic facies of the Ardath "Shale", which is interpreted as the floor of a fossil submarine canyon. Because petrographically similar sandstones occur above and below this surface, the beach-cliff outcrop was everywhere mapped as Torrey. Attention to bedding thicknesses and physical and biogenic sedimentary structures reveals that the sandstones below and above the newly recognized sequence boundary have very different character.

Of special interest is the variegated-fill channel system contained within the boundaries of this "Eocene Torrey Submarine Canyon"; the system is proposed as a submarine canyon facies model. Moreover, the unconformity that defines the boundaries of the canyon is the same age as bounding surfaces that contain canyons on several other continents, implying that they all formed during the same eustatic fall in sea level at about 49.5 million years ago, and all were the conduits that delivered coarse-grained sediments to coeval deep-basin submarine fans.

SEMINAR - Jennifer Lewis

Wide-azimuth seismic at the subsalt Jack asset: Is it worth the early investment?

Jennifer L. Lewis
Chevron Energy Technology Company, Houston, USA

April 9th, 2008

For decades, hydrocarbon accumulations beneath the Gulf of Mexico allochthonous salt canopy were largely considered implausible. The paradigm shift that success could be achieved in deepwater subsalt settings began in 1990 with the subsalt Mica discovery. Today, besides an expanding exploration portfolio, industry has the fortunate task of facing the many and variedfocusing on challenges of subsalt appraisal and development. With this transition comes the need for robust and accurate subsurface characterization. Beneath a salt canopy often many thousands of feet thick, this is a challenge from many viewpoints, from drilling and reservoir management to seismic imaging.

Answers to new and increasingly detailed questions are sought in an effort to minimize risk and optimize project value at a Chevron-operated Deepwater Gulf of Mexico field called Jack. The seismic data quality covering the field is typical of many subsalt images. Data at the reservoir level are low frequency (~10 Hz dominant) and contaminated with remnant multiple noise, making characterization of key reservoir uncertainties, e.g., faulting, an onerous undertaking at best. Recently, industry has recognized a step-change improvement in subsurface imaging in deepwater subsalt settings with wide-azimuth (WAz) towed streamer acquisition and processing. IntegratePresented with the opportunity for a similar improvement in the data quality over the Jack field, an integratedd modeling effort was undertakens, which includedincluding simple 1D synthetics, 3D ray tracing, and 2.5D finite difference models. While these analyses , facilitate the understanding comprehension of the advantages as well as the limitations of proposed WAz survey designs, they are not able to directly aid in the determination of the value that the improved data quality may have to the project. To help address the value of information, a parallel reservoir modeling project was conducted to, while simulated reservoir production models address the implications of acquiring a WAz survey prior to development decisions. Together, Tthese models provide an integrated analysis that can be used to means of effectively communicateing the impact and value of a WAz investment early in the appraisal phase of a project.

Pat Abbott Receives the Pacific Section SEPM Lifetime Achievement Award

Pat Abbott was presented with the A. Eugene Fritsche Lifetime Achievement Award from the Pacific Section SEPM at the AAPG Pacific Section meeting in Bakersfield. Presenter was Dr. Mario Caputo, Pacific Section SEPM's Secretary, Newsletter Editor, and Publication Sales Manager. Abbott is 3rd recipient of this prestigious award in recognition of his untiring devotion and service to the Pacific Section SEPM society. Pat served as President in 1989 and authored/edited serveral publications over his career here at SDSU.