April, 2001
HGS Meetings

HGS Dinner Meeting

"Case History: Amberjack A16ST (T) Well Pore Pressures"

Abstract:

The Amberjack field (Gulf of Mexico: Mississippi Canyon 109) was originally drilled in the early `90s. A second phase of drilling began in 1998, with each well in the program presenting a unique set of challenges to the Amberjack team. In this presentation, the pore pressure case history of the first of the wells in this program is discussed.

Pore pressure work on the field, using offset well RFT, sonic and resistivity data indicated a pore pressure uncertainty range of 3 ppg, around which the A16ST (T) well had to be planned. For a well that was initially considered to be in a development/production setting, a surprising number of complications entered the planning process.

During drilling, pressures were monitored using resistivity and well performance data: the well had to be sidetracked to reach TD. A post-well pore pressure interpretation is proposed in which a series of pressure ramps were drilled in this well. This conclusion is reached through the integration of all available pressure data sources in the well.

Biographical Sketch:

Vanessa Sturrock has an MA in Natural Sciences, specializing in geology, from Cambridge University, England. After graduating in 1990, she spent a brief period working for Shell UK, before joining BP in 1993. Initially, Vanessa worked in exploration and operations geology in Vietnam, and then development geology in Venezuela. Since coming to Houston in 1996, Vanessa has been working in petrophysics, first on the Troika development, and then the Amberjack project, deepwater Gulf of Mexico. She currently works as the Subsurface Team Lead for the Amberjack Field.

HGS Environmental / Engineering Dinner Meeting

" Expert Witness Testimony and Trial Exhibits "

Abstract:

Engineers and scientists often are called upon, sometimes involuntarily, to provide expert or fact testimony. This presentation covers many of the issues in the preparation and delivery of testimony. A number of issues will be discussed, including document creation and retention, work product quality, exhibit preparation and communications. Adherence to a few basic principles will ensure that testimony will be clear, concise, and effective. These issues will be discussed using real-life examples of the pitfalls and effective methods of exhibit preparation.

Biographical Sketch:

Mr. Reed obtained a Bachelor of Geology, from Northern Arizona University in 1970 and a Master of Geology, from Northern Arizona University, in 1976. He has 25 years experience in the environmental and ground water resource consulting arena, serving in both technical and senior management roles. He has performed hydrogeologic studies throughout the United States and its territories. He has conducted a number of environmental workshops, including a Paris-based training session for worldwide managers of a large international firm. He coordinated a soil and ground water study to determine the impact of the largest domestic fuel spill. He provides litigation support, expert testimony, and regulatory agency negotiations. He has testified in cases before both state and federal courts, and several state agencies and has been involved in negotiations with numerous state agencies and several EPA regions. Mr. Reed has served as office manager, regional vice president and director of national accounts for Geraghty & Miller. Anchor E. Holm , P.E., Centurion Consulting Group, will assist Mr. Reed in the presentation.

HGS International Dinner Meeting

"Thermal Modelling - Oil or Gas? Examples from the Faroes-Shetland (NW Europe) and Casamance (NW Africa) Basins"

Vendors and Posters

Abstract:

From the South China Sea to the deepwater of West Africa, basin modelers frequently predict gas yet oil is found. This presentation reviews where the modeling was in error and how the science can be put right. Examples will be shown of how the oil window may be deeper than traditionally modeled in some basins (e.g. Faroes-Shetland Basin), and how it can be shallower in other basins (e.g. Casamance Basin). In the latter case, the origin of the 2BBO plus oil charge to the Dome Flore discovery is now readily apparent whereas in the past it was necessary to draw on unproven source horizons. The message is that charge risks cannot be properly assessed, in either frontier basins or established plays, until the correct thermal model is applied.

Probably the most difficult task facing the basin modeler is the prediction of an accurate heat flow history. The most widely used method for thermal history prediction involves the use of maturation parameters, e.g. vitrinite reflectance in a kinetic model. With time provided by the stratigraphy, the thermal history is obtained by comparing the predicted and observed vitrinite reflectance data and adjusting the thermal history so that the predicted and observed values are the same. This can rarely be achieved without violating the thermal predictions of the basin subsidence models developed by authors (McKenzie, 1978), or without incorporating anomalies such as a heat flow pulse (Jensen and Doré, 1993). In some cases the basin subsidence thermal history models are ignored and a constant heat flow is applied. Geologists then have to devise other features so as to account for the hydrocarbon occurrences, for example, ‘holding tank’ (Doré et al., 1997) or ‘whoopee cushion’ models (Iliffe et al., 1999) in the Faroes-Shetland Basin.

As there is much more mass in the rocks than the vitrinite, the subsidence and exhumation histories of the rocks in a basin must provide the primary source of information from which the heat flow history can be determined. However, the vitrinite reflectance values predicted by heat flow histories obtained from tectonic models are much higher than the observed values. This has led geochemists and basin modelers to question the accuracy of tectonically derived heat flows (Yalçin et al., 1997; Waples, 1998). As there cannot be two different heat flow histories for any one point in a basin, discrepancies will occur between the heat flows obtained by the tectonic and the maturation calibration methods, mainly as a result of a flaw in the kinetic models used for heat-flow modeling. Removing this flaw allows the use of a single heat flow history to predict both the tectonic development and the maturation and hydrocarbon generation histories.

The kinetic models used for maturation assessment assume that time and temperature control the reactions. However, these models fail to recognise the importance of pressure in a gas phase reaction. Vitrinite generates gas during maturation and while an increase in temperature increases the rate at which the reaction proceeds, increasing pressure reduces the rate at which the reaction occurs (Carr, 1999). This relationship between the influences that temperature and pressure have on a chemical reaction is known as Le Chatelier’s principle. As high pressures retard maturation, the incorporation of pressure into a kinetic model (PresRo©) enables the vitrinite reflectance data to be modeled in high-pressure basins such as the Faroes-Shetland Basin. The thermal model developed for this basin contains elevated heat flows during the three periods of Cretaceous rifting, a further period of heat flow associated with end Paleocene volcanism and a smaller event associated with the Oligo-Miocene compression that exists along much of the NW European Atlantic margin. The use of the PresRo® model overcomes the problem observed by modelers using a non-pressure dependent kinetic system, namely that while their models indicate the source rocks should have generated significant quantities of gas, the hydrocarbon discoveries contain very little gas (GOR ~ 0.1). The PresRo© model indicates that the maturation and hydrocarbon generation of the source rocks is being retarded by the high pressures in the basin, and oil as opposed to gas, will be the main product generated.

In the case of shelf margin basins in northwest Africa, e.g. the Casamance Basin of southern Senegal and northern Guinea-Bissau, the sedimentary succession is rarely overpressured although, as in overpressured basins, the vitrinite reflectance values of the main source rock (Cenomanian-Turonian) are generally low (< 0.6% Ro). The source rock, therefore, appears to be relatively immature in the region of the Dome Flore oil discoveries, which contain approximately 1x109 BBLS of 12-13º API (biodegraded) oil. It is also impossible to model the maturation of the wells in this area with a heat flow history based on the tectonic development of the basin. However, the reflectance values obtained from these organically rich (Type II kerogens) source rocks are suppressed and removing the effects of this suppression enables a heat flow history based on the McKenzie (1978) rift model to be used. The Cenomanian-Turonian source rocks are actually mature for oil generation over a significant proportion of the shelf. Given the quality and extent of these mature source rocks and the emplacement of at least 2x109 BBLS of 35º API oil prior to biodegradation, there is no need to invoke the presence of an alternative source rock. Figure 1 illustrates, for the Dome Flore region, the previously applied top peak oil window and the shallower, corrected oil window. The difference is 900 meters.

In the Faroes-Shetland and Casamance Basins the maturation modeling forms part of a single consistent model that accounts for both their tectonic development and their hydrocarbon generation. The ability to model independent parameters, e.g. tectonics and maturation within a single heat flow history is an indication of the accuracy of the thermal model. Finally, the use of an accurate thermal model reduces the risk associated with hydrocarbon generation and produces an overall improvement in the understanding of the Petroleum Systems operating in a basin.

References:

Carr, A. D. 1999. A vitrinite reflectance kinetic model incorporating overpressure retardation. Marine and Petroleum Geology, 16, 353-377.

Doré, A.G., Lunden, E. R., Birkeland, O., Ellassen, P. E. and Jensen, L.N. 1997. The NE Atlantic Margin: implications of late Mesozoic and Cenozoic events for hydrocarbon prospectivity. Petroleum Geoscience, 3, 117-131.

Iliffe, J.E., Robertson, A.G., Wynn, G.H.F., Pead, S.D.M. and Cameron, N. 1999. The importance of fluid pressures and migration to the hydrocarbon prospectivity of the Faeroe-Shetland White Zone. In: A.J. Fleet and Boldy S.A.R. (eds.) Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference. Geological Society, London, 601-611.

Jensen, R.P. and Doré, A.G. 1993. A recent Norwegian Shelf heating event - fact or fantasy? In: A.G. Doré et al. (eds.) Basin Modelling: Advances and Applications. NPF Special Publication 3, Elsevier, Amsterdam, 85-106.

McKenzie, D. 1978. Some remarks on the development of sedimentary basins. Earth and Planetary Science Letters, 40, 25-32.

Waples, D.W. 1998. Basin modelling: how well have we done? In: Duppenbecker, S.J. and Iliffe, J.E. (eds.) Basin Modelling: Practice and Progress. Geological Society London Special Publication No. 141, 1-14.

Yalcin, M.N., Littke, R. and Sachsenhofer, R.F. 1997. Thermal history of sedimentary basins. In: Welte, D. H., Horsfield, B. and Baker, D. R. (eds.) Petroleum and Basin Evolution, Springer, Berlin, 73-167.

Biographical Sketch:

Dr. Andrew (Andy) D. Carr obtained a BSc in Geology from Swansea University and a PhD in Organic Geochemistry from Newcastle University in 1978. Worked for 16 years with BG, left in 1996 to form his own consultancy (Advanced Geochemical Systems). Recently, in conjunction with colleagues, he has set up an integrated service company (Global Exploration Services).

Andy works mainly as a petroleum geochemical and basin modelling specialist in teams involved in prospect and basin evaluation. More recently he has tended to specialize in predicting heat flow histories for other basin modelers to model hydrocarbon generation, and this presentation discusses the heat flow history and its implication for the understanding of hydrocarbon generation and petroleum systems in the Faroes-Shetland and Senegal-Guinea Bissau Basins.

Global Exploration Services Ltd., Little Lower Ease, Cuckfield Road, Ansty, West Sussex, RH17 5AL, UK (telephone: 011-44-1509-881284, e-mail: andy@globalexplor.com .

Posters:
Poster #1:
"Investigation of a Neogene Petroleum System in the Ragay Gulf, GSEC 76: A Frontier Province in the Philippines"
by Linda Sternbach, Globex Energy and John Conolly, Petrofocus, Sydney, Australia

Poster #2:
"Regional Study of the Ragusa Platform, Sicily and Malta".
by Frederik E. Dekker, President, Wessex International.

Vendors:
Vendor #1:
GETECH, Sugarland Texas. Regional grav mag study of the MSGBC Basin, NW Africa and the NAMBA (North Atlantic Margins Basin Analysis) Study.
Contact: Mark E. Odegard, 281 240 0004 meo@getech.com

Vendor #2:
FIRST EXCHANGE Example seismic lines --
reprocesed 2D &3D from the Guinea Bissau Salt Basin and the Dome Flore 1 BBO heavy oil discovery and newly acquired Deep Water 2D Spec Program off Guinea Bissau.
Contact: rogers@fortesa.com , 281 556 5656

HGS Lunch Meeting

“From the Depths” - Texaco’s Petronius Project

Figure: Petronius Production facility

Overview:

Petronius, Texaco’s First Deepwater Development Project, is located in the Gulf of Mexico, 150 miles southeast of New Orleans in Viosca Knoll Block 786. The project suffered a serious production setback when an installation accident occurred in late 1998. Today the field is in its early development phase and is producing significant quantities of oil and natural gas. A history of the field, from Discovery to Present, will be discussed. Topics will include the integration of Geoscience and Engineering technology in the field’s development, construction and installation challenges and achievements, and the benefit of Inter-company workflow processes and Integrated Project Teams.

Biographical Sketch:

Jim Gagliardi, Development Manager of Texaco’s Petronius Field (Viosca Knoll 786, GOM), is currently leading the Project’s successful startup and on-going development drilling program. Jim has 22 years of professional and managerial experience and has most recently served as Offshore Shelf Exploration Manager and Producing Exploitation Area Manager. Early career assignments have included working as a development and exploration Geoscientist in the Gulf of Mexico, the interior Onshore Gulf Coast basins, and in the Appalachian and east coast Triassic basin areas.

Gagliardi holds a Master of Science Degree in Petroleum Geology and a Bachelor of Arts Degree in Geology and Anthropology from the State University of New York. Jim has been an active member of the American Association of Petroleum Geologists since 1980 and has recently served as a Subsurface Steering Team Member on the Upstream Industry Benchmark Committee (UIBC). Jim can be reached at (713) 432-3367 or GagliJS@Texaco.com .

HGS North American Exploration Dinner Meeting

"The Development of Large Structures in the Deepwater Northern Gulf of Mexico "

Figures:

Abstract:

Introduction

An exciting new structural model, based upon a regional structural analysis of the Gulf of Mexico and the integration of well, seismic, gravity, and biostratigraphic data, has been developed for the Gulf. This model has led to the recognition and prediction of large-scale structures in the western Gulf of Mexico.

The central and western Gulf of Mexico are characterized by thick late Tertiary clastic depositional sequences. It is proposed that the accommodation space for these clastics was controlled by the southerly flow of the Jurassic autochthonous (mother) salt. The salt moved by internal flow away from the clastic depocenter and resulted in near surface elevation (inflation) of the mother salt layer. The southern extent of this inflation was probably related to the depositional extent of the salt. An inflated salt model creates the potential to generate large-scale structures during subsequent differential deflation of the salt body.

Structural Provinces

The evolution of the deepwater US Gulf of Mexico will be described by dividing the area into six structurally distinct provinces:

  1. Atwater or Mississippi Fan fold-belt. An area of continuous mother salt inflation with local deflation.

  2. Mississippi Canyon: Mother salt inflation during the Jurassic to Miocene interval. Areas of local partial deflation during the Miocene and Pliocene.

  3. Walker Ridge: An area dominated by thin mother salt withdrawal and consequently the development of low-amplitude structures. The structures and hence salt withdrawal occurred before the emplacement of the main salt canopy, thus suggesting that the main bulk of the salt was derived from the north.

  4. South Keathley Canyon: This area is dominated by a shallow salt sheet that was derived primarily from the south. Partial deflation of this canopy to form mini-basins means that imaging sub-salt is very difficult. However, where imaging is possible, structures are very difficult to see, which suggests either that structures did not develop or that they have less relief than those to the east in Walker Ridge. The lack of structures may imply that the mother salt was either not deposited or was very thin. Clearly there is no evidence to suggest that the mother salt was inflated at any stage since deposition of the salt.

  5. Perdido: Extra-salt, the Perdido fold-belt is superimposed on the southern flank of a large inflated mother salt pillow that formed during the Oligo-Miocene. To the north of the fold-belt a series of shallow salt sheets are interpreted. In some areas, it is possible to see that the sheets have been emplaced since the Cretaceous; they have also been locally folded by the underlying fold-belt.

  6. Auger area: This area is dominated by a thick late Miocene to Pleistocene interval. An interpretation of gravity, magnetic, and refraction data suggest that basement is at about 50,000 ft depth. A comparison between the subsidence profiles for the Auger area and the abyssal plain is useful because the abyssal plain subsidence equates to regional basin loading/crust cooling subsidence whereas the Auger area subsidence will equate to regional subsidence as well as salt withdrawal. A relatively thick Late Miocene-Pleistocene interval in the Auger area suggests mother salt deflation. An interpreted thin Late Jurassic-Middle Miocene interval suggests mother salt inflation.

    Areas 3 and 4 to the south are overlain by a thick salt sheet that was largely emplaced during the Plio-Pleistocene, and the majority of the salt within these sheets must have been derived from the Auger area. The subsidence profiles imply that this salt must have been derived from the mother salt and not from shallow, poorly connected salt sheets. The suggestion of mother salt withdrawal implies that large mother salt-related structures should have developed in the Auger area. Trap types that are likely to have developed include: pillows, turtles, extensional faults, compressional features, and salt ridges. In western Garden Banks, differential withdrawal resulted in the formation of northeast-dipping slope that began to fail by gravity sliding.

Discussion

Deposition of thick early Tertiary clastics under the present-day shelf resulted in the formation of a laterally continuous, inflated pillow of mother salt that extended from the Atwater fold-belt in the eastern Gulf of Mexico to the Perdido fold-belt in the west (Figure 1). Virtually the whole of the northern deepwater Gulf was underlain by this thickened mother salt (Figure 2) which was overlain by anomalously thinned Paleogene sediments. During the late Tertiary, another major phase of sedimentation resulted in thick clastics being deposited on the northern edge of the big mother salt pillow. The pillow, constrained by the depositional limit of the salt, could only deflate by vertical movement (Figure 3). Most of the salt was emplaced toward the south to form the enormous Sigsbee salt sheet; some of the mother salt rose vertically to shallow depths where minor near-surface salt sheets amalgamated. Differential withdrawal from the mother salt resulted in the formation of large pillows that fed the near surface salt sheets via stems. This late salt movement deformed what were once much more laterally extensive, connected clastic deposystems.

In the western Gulf of Mexico, Late Pliocene-Pleistocene salt sheets dominate the near surface stratigraphy. This proposed salt model indicates that in many parts of the western Gulf of Mexico, these salt sheets could be relatively thin, and linked with the movement from deep mother salt pillows/salt-cored ridges. There is the potential for large structures to be associated with this movement. However, actually imaging those structures through the near surface salt sheets in the western Gulf is difficult.

Conclusions

  1. The northern deepwater Gulf of Mexico was underlain by an inflated mother salt interval. This inflation resulted in the deposition of a thin overlying sedimentary sequence.

  2. As sedimentation continued during the Late Miocene to present day, deflation of the mother salt occurred, generating accommodation space for anomalously thick reservoir sequences. This deflation also caused the formation of large structure beneath the overlying salt canopies (Figure 3).

  3. This model is supported by seismic in the central Gulf. It can be inferred that a similar mechanism occurred in the poorly imaged western Gulf.

Biographical Sketch:

Steve Hall graduated in 1977 from Leeds University (UK) with a first class honors degree in geological sciences, Steve continued on to complete a PhD at Imperial College, London University. The PhD involved structural geological and basin evaluation in southeast Spain.

On joining BP in 1983, Steve spent his first five years undertaking structural regional review projects, mainly in South America, UK and France. The following five years were spent working in the international structural geology group based in London. In 1994, Steve formed StrucOil and since then has worked in areas as diverse as the Caspian, the Philippines, Venezuela, Colombia, the Middle East, UKCS, India, Mexico, Mauritania and the US Gulf of Mexico. Steve has spent the last 6 years working with BP on complex salt problems in the deepwater Gulf of Mexico.

THE SOCIETY OF PETROLEUM EVALUATION ENGINEERS Lunch Meeting

“California’s Electricity Woes: A Vision of the Future?”

Abstract:

California has long been in the vanguard of national trends. Since mid-2000, California has experienced a considerable number of problems with its electricity market, including fluctuating prices and shortages. California’s electricity woes give us a reason to take pause and consider the future of U.S. electricity markets and of energy policies in general.

Electricity is an important part of the U.S. energy infrastructure-accounting for more than one-third of U.S. energy consumption. If other states experienced problems with their electricity markets similar to those in California, the effects would be felt throughout the economy.

Nearly half the states are restructuring their electricity markets, and many more are considering doing so. Eight states have already implemented restructuring of their electricity markets. Sixteen states and the District of Columbia have enacted legislation or issued regulatory orders that will restructure their electricity markets. Eighteen states are investigating the possibility of restructuring their electricity markets. Only eight states are not currently taking any steps toward electricity market restructuring.

The problems with the California electricity market are the result of several factors, including a poorly devised restructuring that took place nearly three years ago. As the states progress toward restructuring their electricity markets, we should ask: Are California’s electricity woes a dark vision of the future or an isolated incident in a state where policymaking was not sufficiently informed by economic reality?

Biographical Sketch:

Stephen P. A. Brown is director of energy economics and microeconomic policy analysis at the Federal Reserve Bank of Dallas. In this position, he conducts and manages economic research and analysis. He also briefs the Bank's president and board of directors on economic conditions and policy. His management responsibilities include energy economics, microeconomic public policy and the Bank's publications Economic and Financial Review and Southwest Economy.

He holds a B.S. in economics from California Polytechnic State University and an M.A. and Ph.D. in economics from the University of Maryland. He also has completed a number of leadership training programs, including the executive development program at the Federal Reserve Bank of Dallas and several at the Center for Creative Leadership in Greensboro, North Carolina.

Brown is the author of numerous articles on economic policy, economic theory and business conditions. His research focuses primarily on energy, environmental and natural resource economics, microeconomic public policy and economic conditions. His articles have appeared in such publications as Business Economics, The Energy Journal, Contemporary Economic Policy, Economic and Financial Review, Journal of Environmental Economics and Management, Public Choice and Southwest Economy.

His work has received national and international attention from academia, the business community, government and OPEC. He has been quoted in various regional publications, as well as in Business Week, the Economist, Financial Times, Newsweek, The New York Times, Time, The Wall Street Journal and Marilyn vos Savant's book, The Power of Logical Thinking. He also has appeared on various regional broadcasts in addition to CNN's Financial Report, ABC's Financial World, the McNeil/Lehrer NewsHour, Public Radio International's Market Place, and the PBS series Man, Energy and the Environment. He has made numerous presentations to academic, civic and professional groups, including members of the British Parliament.

Brown joined the Federal Reserve Bank of Dallas in 1981, after working as an energy economist for Brookhaven National Laboratory and teaching economics at several universities. In addition to his principal position, he serves as an adjunct professor of economics at Southern Methodist University. He also serves on the advisory board for the College of Business at California Polytechnic State University.

He is a member of the American Economic Association, Western Economic Association, International Association for Energy Economics and Public Choice Society. He has also participated in the Energy Modeling Forum at Stanford University and the International Energy Workshop. He recently served on the economic review panel for the National Petroleum Council study of future issues in the oil and gas industry. Brown plays guitar and, with his wife, dances and teaches Argentine tango.