HGS Environmental / Engineering Section Dinner Meeting

"The Texas Risk Reduction Program Rule - The Next Step in Risk-Based Corrective Action"

Author: by Paul S. Lewis, TNRCC

Date: Wednesday, June 14, 2000

Place: Jalapeno's - 2702 Kirby (at Westheimer)

Time: 6:30 - 7:45 PM - Dinner; 7:45 - 8:45 PM Presentation & Q/A

Cost: $17.00 per person for a full dinner including tip. Dinner is optional.

Note: This is a must-attend lecture that will supplement your knowledge of the TRRP and how the program works. Don't miss out on great food, great discussion, networking, and employment possibilities.

The presentation will summarize the key features of the Texas Risk Reduction Program (TRRP) rule promulgated in September, 1999, by the Texas Natural Resource Conservation Commission (TNRCC) for governing the remediation of contaminated sites. The regulations governing contaminated site cleanups have been incorporating increasingly sophisticated methods to develop cleanup levels.

Historical practice in Texas had been to require cleanup to background concentrations or, failing that, to contain the contaminated area as a landfill. After 1993, state regulations combined these historical practices with risk assessment methodologies to define three distinct risk reduction standards for industrial waste sites. Next came a receptor-based process for petroleum release sites which was patterned after the American Society for Testing and Materials' Risk-Based Corrective Action standard. If the same contaminant were evaluated by both of these programs, different cleanup levels would result due to some significant differences between regulations.

In response to this discrepancy, among other reasons, the TNRCC has drawn upon the implementation experience from these two approaches and has promulgated a new set of regulations, known as the Texas Risk Reduction Program rule, that will be applied to most remediations regulated by the agency. There will be two basic remediation standards that vary the response actions according to the use of control mechanisms. The derivation of cleanup levels will utilize a three-tiered process that will be independent of the remediation standard. The tiered process for human health protection starts with conservative assumptions regarding the frequency and duration of exposure to develop generic Tier 1 protective concentration levels. In Tier 2, certain site-specific information can be utilized in analytical fate and transport models to be specified in guidance. Tier 3 will afford the user the greatest degree of site specificity and modeling flexibility. A three-tiered process has also been developed for protection of ecological receptors.

The TNRCC expects this new rule to help expedite cleanups by addressing the investigation of contaminated sites, establishing reasonable requirements for public notice, streamlining the calculation of site-specific cleanup levels, and setting forth appropriate remedy standards. A copy of the complete rule package can be obtained from the TNRCC website at http://www.tnrcc.state.tx.us/permitting/trrp.htm

Biographical Sketch:

Paul S. Lewis, is Unit Manager of the TNRCC Technical Support Section, Remediation Division of the Texas Natural Resource Conservation Commission. He graduated from Widener College with a B.S. degree in management in 1972. After two years of military service in Texas, he entered the University of Texas at Austin and completed an MA degree in geology in 1978. He began his career with Pennzoil in Houston as a reservoir development geologist in 1977. He joined the Texas Department of Water Resources in 1979. His duties with the Commission and predecessor agencies have varied between technical and management positions, including Manager of the Corrective Action Section from 1992 to 1998. He chaired the committee of staff volunteers who developed the 1993 risk reduction rules and was part of the rule-writing team for the new Texas Risk Reduction Program rule. His current assignment as a technical specialist includes developing guidance and training for the new Texas Risk Reduction Program rule.

International Section Dinner Meeting

"The Rio Mini Basin of Equatorial Guinea - a new hydrocarbon province"

Authors: Paul Dailly and Kenny Goh Triton Energy

Date: Monday, June 19, 2000

Place: Westchase Hilton, 9999 Westheimer

Time: 5:30 Social 6:30 Dinner

Cost:

Introduction

The Rio Muni basin underlies the continental shelf of the West African Republic of Equatorial Guinea, located between Gabon and Cameroon. The basin is located above a zone dominated by northeast-southwest trending oceanic fracture zones and their continental extensions. These constitute the boundary between the Equatorial Atlantic margin and the West African salt basin. This tectonic setting has resulted in the Rio Muni Basin exhibiting a complex tectonostratigraphy which exhibits characteristics of both the 'passive margin' style of Gabon and Angola, and the more transform dominant style of the northern Gulf of Guinea.

Exploration History

Despite its location between the prolific hydrocarbon provinces of the Niger delta to the north and the Gabon coastal basin to the south, the Rio Muni Basin has been overlooked by the industry over much of the last decade. Six wells were drilled between 1968 and 1991 in the shelfal and onshore areas of the basin. These focused on Albian and Aptian objectives and although they proved a viable source rock, did not result in the discovery of any accumulations. In 1997, following a review of the West African margin, Triton Energy licensed Blocks F & G, which comprise an area of 5270km2, covering both the shelf and deepwater areas in the central part of the basin. Following acquisition and interpretation of new 2D seismic data, the Ceiba 1 exploration well was drilled in 1999 and proved a working hydrocarbon system in the post rift sequence. This establishes a new and high potential oil play in this part of the Gulf of Guinea.

Tectonostratigraphy

The tectonostratigraphic evolution of the basin can be divided into a number of separate phases. To date no wells have penetrated strata older than Middle to Late Aptian and clear definition of the nature and age of an early rifting or trans-tensional phase is lacking. Despite this there is limited seismic evidence to support differential subsidence of possible Early to Mid Aptian age. This is overlain by a thick, Late Aptian continental/lacustrine succession followed by Albian-Cenomanian aged marine section. The upper part of the succession appears to be regional in extent and is likely the result of 'postrift' subsidence.

Following the onset of postrift subsidence, the Albian-Cenomanian sequence was locally deformed into a series of rafts which detach on a basal Albian organic rich claystone section. Further deformation by Santonian-Coniacian transpression caused uplift of the shelfal area and deposition of a Late Cretaceous, slope fan sequence. This is overlain by a Tertiary passive margin wedge, deposition of which was punctuated by renewed uplift and erosion at the base of the Neogene. Present day basin architecture is dominated by a series of NE-SW trending highs and lows that developed in response to the basal Senonian and Neogene events. The highs resulted initially from Santonian-Coniacian aged inversion of Aptian deposits underlain by the continental extension of NE-SW fracture zones. In addition, salt deformation of rafted deposits and the development of a base of slope compressional belt are evident in the deeper water portions of the basin.

Petroleum Geology

Late Cretaceous tectonism and base level change resulted in the development of turbidite reservoir sequences associated with a series of Late Cretaceous sequence boundaries. These turbidites form the reservoir in the Ceiba discovery, which was tested at a rate of 12,400 bopd. Both Late Cretaceous and Tertiary turbidite reservoirs form the major exploration targets in the basin and are situated in a variety of structural and stratigraphic trap types. These exploration targets are thought to be accessible to a deepwater source kitchen from which earlier shelfal wells were shadowed.

Biographical Sketch:

Paul Dailly graduated with a BSc (Honors) in geology from Edinburgh University in 1985, and a PhD in basin analyses and structural geology from Oxford University in 1990. After 6 years at BP Exploration working exploration and appraisal projects, he joined Triton Energy in 1995 as a senior geologist, working on a variety of international new ventures and exploration projects.

During the last 2 years, Paul has been project geologist for Triton's Equatorial Guinea licenses and West African new ventures.

Kenny Goh graduated in 1980 with a BSc (Hons) in applied geology from the University Malaya, Kuala Lumpur, Malaysia. He has 21 years of international experience as a Geophysicist with PETRONAS, Carigali/Shell, Sun Oil International and Triton Energy.

Currently he is chief geophysicist for Triton Energy with responsibility for both Triton's Malaysia-Thailand joint development area gas fields and equatorial Ceiba oil field discoveries.

POSTERS:

Poster 1:

"Paleo Congo River Fan in Northern Gabon, Upper Cretaceous Mini-Basins and Fold Belt"
K A Nibbelink and S Budihardjo, with contributions from: A D Scardina, J D Huggard, S P Stoutimare, S F Deetz, SantaFe-Snyder

Poster 2:

"Integrating seepage patterns found on satellite radar with offshore Tertiary sediment load factors derived from onshore drainage and satellite gravity analysis ranks S. Atlantic basins and predicts Rio Muni success".
Mike Oehlers, NPA, Nick Cameron, GeoInsight, Ed Purdy, Petroquest, and John Milsom, UCL.

Poster 3:

"Examples of Salt Tectonics from West Africa: a comparative approach."
Gabor Tari, Jim Molnar, Paul Ashton Vanco Energy, Houston, Texas, Richard Hedley Lasmo, London, United Kingdom

The application of salt structure concepts developed in specific salt basins to all salt basins along the West African margin must be used with caution. To conduct a comparative structural analysis, regional reflection seismic transects were constructed across the salt basins of Morocco, Equatorial Guinea, Gabon and Angola.

In the post-rift salt basins of Equatorial Guinea, Gabon and Angola, updip extension is represented by a broad rafted domain. The extension is balanced by downdip contraction in form of salt tongues, sheets, canopies and the progressive inflation of a massive salt domain at the basinward edge of the salt basin. The efficiency of this gravity spreading across the whole margin is due to the more or less uniform original distribution of Aptian salt in the post-rift succession forming a continuous detachment level. In contrast, the uneven original distribution of the Upper Triassic and Lower Jurassic syn-rift salt in Morocco is due to the basement highs separating rift half-grabens creating a different structural pattern. Individual salt structures such as tongues, sheets and canopies originated from isolated patches of the autochthonous salt. In the case of syn-rift salt, updip extension may not be the ultimate driving force for the contractional salt deformation downdip. Consequently, the compressional anticline at the edge of the salt basin may not be a sensu stricto toe-thrust feature due to the lack of a basin-wide detachment efficiently linking all the salt structures together. In addition to the direct comparison of cross-sectional geometries, the map-view expression of salt tectonics were compared in Morocco and Angola representing basin types with syn-rift and post-rift salt sedimentation, respectively. Local salt geometries in relation to possible hydrocarbon trap types were also comparatively analyzed within these basins. The similarities and differences have important exploration implications.

In conclusion, regional-scale similarities of the salt basins include the progressive complication of salt-related structures basinward, the change from an extensional domain in the shelf to a compressional domain in the slope, and the presence of a toe-thrust front at the oceanward edge of the basins. Regional-scale differences are partly attributed to the relative stratigraphic position of the salt in relation to the rifting of the margin. Additional factors which appear to influence the salt-deformational styles include the underlying basement structure, the original thickness and map-view distribution of salt, the timing of regional basinward tilt, the sedimentary loading history of the margin and, specifically, the proximity to major sediment entry points into the basin."

Poster 4:

"New prospects in the Gulf of Guinea post-rift petroleum system (Equatorial Guinea and Cameroon)"
S. R. Lawrence1, A Soulsby2, R. J. Bray2 (1) Exploration Consultants Ltd, Henley-on-Thames, United Kingdom (2) Exploration Consultants Ltd

Recent deepwater licensing rounds in the Gulf of Guinea have focused attention on the emerging Cretaceous post-rift play. Here, the post-rift section comprises "transitional" (Aptian-Albian) and "early drift" (Cenomian-Santonian) sequences. Good oil-prone source rocks are proven in the Aptian-Albian section and are inferred in the Cenomanian-Turonian section from regional extrapolation and geochemical data from reservoired oils and surface seepages. An important post-rift structural episode occurred in the Santonian, involving transform reactivation and differential uplift causing extensive gravity-sliding. Large scale gravity-slide features characterize large areas of offshore Rio Muni and southern Cameroon. Cessation of this structural event is demarked by the "Senonian Unconformity".

The Kribi oil and gas and Sanaga Sud gas/condensate fields occupy gravity-slide structures. Hydocarbons probably migrated from source rocks in downdip/subjacent intra-gravity-slide or downdip extra-slide locations. Hydrocarbon type and quality can be explained by laterally-varying maturity histories. In deepwater locations, in front of gravity-slides, less complex burial and maturity history is dominated by post-Senonian unconformity burial. Source rocks here are in "late oil" to gas mature conditions, favourably located below predicted reservoir development within seismically defined Upper Cretaceous and Lower Tertiary base-of-slope/basin-floor fan systems.

Much oil remains to be discovered from this post-rift petroleum system in the deep water Gulf of Guinea region.

Poster 5:

"Proto-Oceanic Crust - Defining and Naming a Trend from Congo to Benin"
Bill Dickson, Dickson International Geosciences (DIGs), Houston Tx and Mark Odegard, GETECH, Stafford Tx

Plate reconstructions have played an important role in defining areas of crustal fit and misfit. A short (68 frame) movie has been constructed based on the plate model of Smith and Bouguer gravity grids from GETECH. Detailed mapping based on these reconstructions revealed a consistent signature in gravity maps over a zone just outboard of the continent-ocean crust boundary (COB). Comparison to published results, which used seismic and potential field data, and discussions with other researchers in the field provided further insight. The proto-oceanic crust (POC) typically shows an architecture of tilted fault blocks and onlapping fill. This poster illustrates the patterns and signature of the zone which has been defined as POC. The POC was likely derived from the emplacement of volcanics at or near sea-level during the final stages of continental separation and was buried by mixture of volcanics and clastics in regions of limited lacustrine to oceanic circulation.

Implications for exploration are the need to alter heat-flow models for maturation calculations and the recognition that some of the reflection events in the half-grabens may be intra-basement, limiting the floor to and hence the volume of prospective source rocks. The upside is the presence of features that provide areas for source and reservoir accumulation with sag and compaction-type structuring tending to create large, low-relief areas within closure.

Poster 6:

Saltpond Field, Ghana: Exploration history and future potential.
Nick Cameron, GeoInsight, and Jeffrey Martin, First Exchange

VENDORS:

Exploration Consultants Limited

Official License Round Promotion and new Regional Studies
ECL are carrying out two new non-exclusive projects to provide new data and assist in the continued exploration of the Rio Muni Basin.
STRUCTURAL AND STRATIGRAPHIC DEVELOPMENT AND SOURCE ROCK MATURATION HISTORY BIOSTRATIGRAPHICAL AND ENVIRONMENTAL STUDY OF THE RIO MUNI BASIN, EQUATORIAL GUINEA, Lacustrine Associates

For more information see the ECL website www.ecqc.com/

Western Geophysical

Key Regional Seismic data across the Rio Muni Basin

Earthmoves Ltd.

South Atlantic Margin Correlation: Looking for the Perfect Fit? Ian Davison, Earthmoves Ltd. (UK), Matthew Taylor, Taylor Exploration Associ ates Ltd.(UK), & Mark Longacre, MBL Inc. Denver.

This project consists of a detailed reconstruction of the South American and African plates to their former positions before continental break up. The work involved surface geology compilation, fieldwork, regional seismic and gravity interpretation to build the best possible digital maps. The fit is unique in recognising and restoring internal plate deformations, which can amount to several hundreds of kilometres of horizontal translation. Computer reconstructions of approximately seventy microplates can be attempted independently of our own preferred fits. Accurate reconstruction maximises understanding of conjugate margins where poorly explored segments are juxtaposed against more mature areas. The original geological and geophysical basemaps will serve as an invaluable reference base for oil companies exploring the continental margins.

For more information please visit our website www.earthmoves.co.uk

North American Exploration Section Symposium

"Understanding Stratigraphic Complexity - the importance to exploration and production"

Date: Monday, June 5, 2000

Place: Westchase Hilton, 9999 Westheimer

Time: 9:00 am - 4:00 pm

Cost: Pre-registration (before June1): $50.00, Pre-registration (after June1): $55.00, Walk-ups: $65.00. Note Lunch Included!

Contact for more information: HGS Office .

Registration Form: Click here

Description:

Reservoir stratigraphy can be difficult to interpret and even more problematic to integrate into production models – when that is further complicated by the influence of syn- and/or post-depositional tectonics, salt movement, etc., the results can be mind boggling! Come and see examples of how these "complications" have been dealt with in various plays around the world.

Who should attend:

Anyone interested in learning more about utilizing 3D seismic and other tools at our disposal to further our understanding of reservoir complexity.