World resource statistics geared for electronic access

C.D. Masters, D.H. Root, R.M. Turner
U.S. Geological Survey, Reston, Va.

This article describes the first public presentation, by basin, of quantitative, worldwide conventional petroleum resource assessments.

These assessments are presented in tabular form along with a world petroleum basin map keyed to the tables. The assessments are now available on a U.S. Geological Survey web site, http://energy.er.usgs.gov/products/papers/world_oil/index.htm.

The USGS World Energy Resources Program (1979-95) was responsible for the World Petroleum Basin map development and for the attributed international resource values; U.S. petroleum resource estimates are derived from the work of a domestic resource assessment team. The international estimates were developed prior to 1994 and published relative to country and to broad geographic area, in the proceedings volume of the 14th World Petroleum Congress, Stavanger, Norway, 1994.

The data were developed by the program scientists and published, subject to technical review, through standard USGS procedures. At different program stages, valuable resource coordination derived from the Energy Information Administration/Department of Energy. Always, resource conclusions derived from program activities were the responsibility of the working scientists. No other government element reviewed or participated routinely in the resource analysis procedures.

Over the years, we encountered many challenges to our resource assessment conclusions and always prospered from the scientific criticism. Clearly, there are legitimate differences of opinion on the assessment of many basins, but, interestingly, more often than not, there has been a commonality expressed as to the quantity of total world petroleum resources. There are, however, detractors at the world level, some arguing for much higher levels and others to the contrary. Our response to the critics demanding the significantly higher levels has been to remind them that such high values, statistically, would require the discovery of the equivalent of new Middle East provinces which we do not believe is possible. For those arguing for lower world values, again the issue revolves around the Middle East and the generally high values we attribute to its identified reserves. The problem here is the lack of public data; the issue cannot be argued, rationally, in the open literature. We fully recognize this scarcity of data and information but are satisfied that having had access, in the past, to convincing original data and, more recently, confirmation from reliable sources, permits us to stand with our reported values, which are comparable to those reported by OPEC.

Introduction

The USGS initiated the World Energy Resources Program (the program continues) to gain information for the U.S. government on world energy resource occurrence.

We knew from the beginning that it would not be possible to develop fully detailed information everywhere but that we could, by focusing on the regionally important areas, develop initial understandings that would serve many information needs and at the same time form a base for in-depth studies as requested or otherwise needed.

The first order of necessary resource understanding is political or economic and developed commonly at the country level. In doing the geologic and/or engineering analysis work, however, our data were collected from fields and wells and reports with information geographically related to geologic entities such as individual basins or provinces.

Thanks to earlier USGS work,^l we had a preliminary map of world petroleum basin distribution. Over the years, we digitized this early basin-boundary work and overlaid it on a proper geographic base to serve as an initial locator for our data development. As work was accomplished, we modified those basin boundaries to our satisfaction. Small-scale presentations of the resulting basin map (Figs. 1 and 2) show by color code the estimated quantities of "futures" oil and gas.

The purpose of this article is to relate the program's history and accomplishments, discuss some of the major ongoing program issues, and acquaint the reader with new data presentations now available on a USGS web site, http://energy.usgs.gov.

Program evolution

The 1970s were trying times for U.S. energy availability, or so it was thought.

In the early part of this decade, OPEC doubled the price of oil and embargoed shipment to the U.S. for a short time. Just how much oil and gas any country actually had was not publicly known, and there was great uncertainty about from where future oil and gas would come.

In 1975, the USGS, at the request of Congress, published its first extensive team evaluation of U.S. petroleum resource potential,² and repeated the activity in 1981, 1987, and 1995.³ The results of the 1995 domestic resource analysis were utilized in our program work.

Because we were producing only a little more than half of the oil we were using, concern about international sources of energy began to mount. The questions about where and how much were easy to ask, but no one had publicly available information with which to respond. To fill this gap, the World Energy Resources Program was conceived, in the late 1970s, in cooperation with the Energy Information Administration of the Department of Energy. We continued to work cooperatively with EIA/DOE in program development, but budgets were never of such dimension, or sufficiently blended, to permit fully coordinated studies.

Our procedures for resource appraisal involve the careful study of all available sources of information and the use, then, of various techniques of quantitative assessment. Upon presentation of the determined petroleum geology and the quantitative options by area geologists, the program scientists as a whole reached consensus on an assessment of Undiscovered Resources following a modified Delphi process.⁴ Similarly, the available Reserves values were examined and subjected to growth calculations or adjustments as deemed appropriate.⁵

Early in the program we responded to particular requests for resource understanding in Nigeria, the Soviet Union, China, and elsewhere. Our program focus, however, was established in 1981 when the World Petroleum Congress invited us to submit a paper for the 11th WPC in London in 1983 on world oil occurrence by country and by major geographic groupings.

Since then, the program focus has been on petroleum resources of the world, and we responded with expanded and updated resource understanding (both oil and gas) at the next three Congresses: WPC 12, Houston, 1987; WPC 13, Buenos Aires, 1991; and WPC 14, Stavanger, Norway, 1994. Table 1 and Table 2 show the results of our last resource assessment for oil and for gas, by country, and by world region as presented at WPC 14.⁶

Though this work was reported geographically by country, the geologic analysis was done with field and well data points located in basins or geologic provinces. Early on, we began to organize data by basin, but we remained obliged by WPC to report by country.

For WPC 14, however, we offered, in a poster session, our first digital world basin map (derived from Coury and Hendricks1 and modified by scientists in the World Energy Resources Program). The basins were colored to show six different levels of "Futures" resource potential for both oil and gas. (Figs. 1 and 2 ).

The reader will note that the range of values in each category is rather large. For example, both the Middle East basin and the West Siberian basin of Russia are shown in the highest category of resource potential, connoting greater than 100 billion bbl of oil. In actual "Futures" numbers, we allot only about 100 billion bbl of "Futures" oil to the West Siberian basin, but we consider the Middle East basin to contain more than 600 billion bbl of "Futures" oil.

On the web site, we offer a vector digital presentation of the basins and other world geographic outlines. Each basin is numbered and keyed to a table showing basin number, basin name, and resource estimates including: Cumulative Production, Identified Reserves, and Undiscovered Resources of both oil and gas.

Almost all international basins have been examined and publications prepared by our program scientists⁷ (see also bibliography on the web site). Some basins have been studied more than once because they are important basins with significant activity; such basins should continue to be updated for credibility.

Having initially evaluated these basins, we, and the public at large, have a base from which to recognize anomalies in data development and hence can quickly recognize potential changes in resource understanding.

It is also true that "mental anchoring" is a reality and new approaches to analysis must be considered. For example, few world marine basins have been analyzed for truly deepwater potential. The ideas and the data are not yet available for anybody but the pioneers in the activity.

Major program issues

We have always presented our program as a scientific endeavor. That remains true, with the significance being that though we were U.S. government employees, we were free to present our findings as we saw fit subject only to peer review as is customary in the USGS.

In conducting its work, the USGS does not take an official supporting position relative to its publications. Rather, the Survey submits that the procedures followed and the data presented in accomplishing the work are legitimate and the analyses are credible. Resource assessment, as for all scientific endeavors, seeks after a truth that will forever be denied, but best judgment-calls, from ongoing program activities, are required to contribute satisfactorily to energy policy.

In this regard, we consider that our program results provide a public point of departure for showing and measuring relative change in resource understanding. Such a resource evaluation is useful to the extent that it presents reliable and credible conclusions. The public response to those assessed values, for the most part, has been subjective, but there are credible numerical critics that believe our assessments to be substantially too low, and there are also those who would argue the opposite.

We readily acknowledge that individual basin analyses may change over time with new interpretations, concepts, and data, but we consider that such changes are likely to balance out with some provinces increasing in value while others, by consistent reasoning, might decrease. For the overall assessed values to be significantly low, however, requires the statistical occurrence of additional basins with Middle East level resource quantities. We would argue that such occurrences are most unlikely.

For the overall values to be judged too high also requires a major Middle East adjustment owing to its dominance in the overall petroleum resource values. With the first WPC publication in 1983, our EIA/DOE petroleum engineering colleagues recognized, from available original data,⁸ just such an adjustment from Aramco data (i.e., a marked increase) as that which subsequently was reported by OPEC in the mid to late 1980s.

Additionally, later pronouncements from the OPEC countries have further enlarged the discovered-resource values, demanding, from our program analysis very high recovery rates. The EIA/DOE scientists suggested these higher values were entirely possible if the fields were properly developed and if the concepts of reservoir quality were sustained.

We know from personal communication in 1995 with Sidney Bowers, a former Aramco Chief Geologist, that production practices have remained of a very high quality, and we know from physical evidence provided by the gulf war torching experience at Burgan field in Kuwait that some reservoir properties also were of a necessary high quality to sustain the open-flow blowouts (associated with the fires) without reservoir damage. We stand by our early high estimates but, of course, welcome expressions of new data that may become available.

In the early stages of program development, we anticipated that natural gas resources, in a BTU sense, would be far greater than oil because of the multiple origins for gas. To the contrary, our assessments show there to be somewhat less gas than oil in the world.

Over the years, we have been unable to discover other significant potential discovery sites for conventional natural gas and consider, therefore, the possibility that fracturing of the earth's crust might preferentially cause the loss of more gas than oil.

It is also possible that the lesser quantities of assessed recoverable gas may be accounted for by considering that large quantities of so-called unconventional natural gas are trapped in the many tight reservoirs, or are dissolved in waters, or bound in ice molecules (clathrates) not herein included in assessed recoverable resources. The reader should be aware in evaluating natural gas resource understanding, that data, generally, are much less complete than for crude oil.

Perhaps the single most important scientific contribution of the program is found in a publication by Ulmishek and Klemme.⁹

The authors concluded that only six narrow stratigraphic intervals, representing one-third of Phanerozoic time, contain the petroleum source rocks that have provided more than 90% of the world's discovered oil and gas. Further, these source rocks, and their associated reservoirs, are restricted in their development to the equatorial regions between the 30° latitudes.

This is so, because good source rock derives from sediments with flourishing organic content-a product of warm waters. And further, carbonate reef rocks, which account for about 50% of the world's reservoirs, are overwhelmingly concentrated between the 30° latitudes for the same warm-water reasons.

The authors also show that plate tectonic movements have been such as to result in a concentration of petroleum resources in the northern hemisphere because over time much of the continental mass previously located equatorially has migrated north.

The southern hemisphere continents (with the exception of their northern extremities such as Venezuela, North Africa, and the Middle East), however, retained their Antarctic attachments and high-latitude position until the Late Jurassic thus denying them a favorable equatorial position until late in Phanerozoic time.

This reality is reflected on our maps of petroleum "Futures" (Fig. 1 and Fig 2). Antarctic basins, tectonically and depositionally, show development similar to favorable basins elsewhere. Because of their high latitude positions and remoteness from markets, however, we choose to consider all of them as having very low probability of commercial petroleum development. The Most Likely or Modal value of undiscovered resource occurrence then being negligible, "Futures" calculations are zero.

To have estimated the general quantities of "Futures" resources is only a part of what's needed by political and economic analysts. Potential rates of production, over time, from particular geographic localities are also useful. Such an analysis was performed by Masters et al. and reported in Science.⁴

Owing to the highly skewed geographic distribution of all mineral resources, we must remain ever alert to the fact that a large part of world petroleum resources derives from a single geographic location, the Middle East, which by 2010 will be responsible for more than one-half of world oil production. Our world economic system is predicated on multiple sources of supply for any and all products. Adjustments in energy type, use, and acquisition will be required (see also Bookout ¹⁰).

The future

Assessments/evaluations of basins are not and cannot be made for all time. The understanding of the assessors is in constant flux, as is, most commonly, the information with which to work.

Three years have passed since the resource values herein presented were developed. The exploration world has not stood still.

We hear of significant discoveries in Algeria and in the deep waters west of the Shetland Islands. We don't know how assessments in those areas may be affected, but there, as well as in all other parts of the world, the reader must remain aware of the continual passing of time and events.

On the other hand, there are basins in which, several years ago, we made evaluations with high expectations, such as the Tarim basin in China; there have been no recent reports of significant discovery there and, at some point, reconsideration of the assigned values may be appropriate.

To varying degrees, the same is true for all basins the world over: the user must remain aware of the changing circumstances and realities. For example, should we expect, around the world, the same levels of field growth we have encountered in the U.S. We think not, because oil development, elsewhere, has not matched the U.S. experience. Rather, careful field development has preceded initial Reserves announcements resulting in minimal later-growth in the Middle East, former Soviet Union, China, and in many offshore or remote producing localities.

These areas overwhelmingly dominate remaining world oil estimates. Hence, though growth is a reality to be considered in many areas, it will not significantly affect overall Reserves quantities as presently calculated.

Web site contents

The described web site presentation contains the following maps, tables, and text:

1. A base map of world political geography with overlying petroleum basin outlines and identifying numbers.

2. Four petroleum "Futures" maps, showing by color variance and by black and white patterns of differentiation, six different quantitative levels of oil and gas "futures" values, from smallest to largest.

3. A world petroleum basin map with overlay, from Petroconsultants data, of oil and gas field locations. The map shows concentration of known oil and gas fields and their geographic positions relative to assigned basin boundaries.

4. Two tables of conventional oil and gas resource values, by basin, showing basin number, basin name, annual production, cumulative production, identified reserves, and undiscovered resources with a range of values from 95% to 5% probability of occurrence and including calculated or estimated values of the Mean and the Mode of the distribution.

5. Bibliography of the USGS program contributions and selected complementary publications.

6. Reprint: Masters et al., 1994, World Petroleum Assessment and Analysis.

7. Reprint: Klemme, H.D., and Ulmishek, G.F., Effective petroleum source rocks of the World: Stratigraphic distribution and controlling depositional factors, AAPG Bulletin, Vol. 75, No. 12, 1991, pp. 1,809-51.

8. Reprint: Masters, C.D. et al., 1997, The World of Petroleum.

Acknowledgments

The preparation of this report and the accompanying digital information emerged from a team effort over the life of the program. Authors are particularly indebted to our petroleum scientist colleagues, including: Emil Attanasi, Mahlon Ball, James Clarke, Oswald Girard, Douglas Klemme, K.Y. Lee (deceased), John Kingston, James Peterson, and Gregory Ulmishek. Contributors from EIA/DOE were: William Dietzman, Gary Long, Jack Sanders, and John Wood.

Digital preparation of the maps for web site presentations was by Robert Turner and Ronald Charpentier. The basic source of raw data for the work has been Petroconsultants.

References

1. Coury, A.B., and Hendricks, T.A. Map of prospective hydrocarbon provinces of the world, East Asia, Australia, and the Pacific, U.S. Geological Survey, Miscellaneous field Investigations Map, MF 1044 A, B, C., 1979.

2. Miller, B.M., Geological estimates of undiscovered recoverable oil and gas resources in the U.S., U.S. Geological Survey Circular 725, 1995, 78 p.

3. U.S. Geological Survey National Oil & Gas Resource Assessment Team, 1995 National Assessment of the U.S. Oil & Gas Resources, U.S. Geological Survey Circular 1118, 1995, 20 p.

4. Masters, C.D., Root, D.H., and Attanasi, E.D., Resource constraints in petroleum production potential, Science, Vol. 253, 1991, pp. 146-152.

5. Masters, C.D., Root, D.H., and Attanasi, E.D., World resources of crude oil and natural gas, in proceedings of the 13th World Petroleum Congress, John Wiley & Sons, Vol. 2, 1992, pp. 229-237.

6. Masters, C.D., Root, D.H., and Attanasi, E.D., World petroleum assessment and analysis, in proceedings of the 14th World Petroleum Congress, John Wiley & Sons, 1994, pp. 529-541.

7. Masters, C.D., Bibliography of the World Energy Resources Program, U.S. Geological Survey Open File Report OF 94-556, 1994, 10 p.

8. Dietzman, W.D., The petroleum resources of the Middle East, DOE/EIA-0395, Office of Oil & Gas, Energy Information Administration, Washington, D.C., 1983, 169 p.

9. Ulmishek, G., and Klemme, H.D., Depositional controls, distribution, and effectiveness of world's petroleum source rocks, U.S. Geological Survey Bull. 1931, 1990, 59 p., six plates.

10. Bookout, J.F., Two centuries of fossil fuel energy, Episodes, Vol. 12, No. 14, 1989, pp. 257-262.

Reserves, resource definitions

1. "Identified Reserves" are interpreted to include not only the traditional Proved Reserves but also any additional petroleum we might conclude will be recognized by field growth attained through extensions, new reservoirs, or improvements in recovery.

Our objective is conventional petroleum resource understanding, not reserves potential in an immediate market sense; we have not considered oil or gas that may not in the future become a part of commercial energy utilization.

2. "Petroleum Futures" are defined as Identified Reserves plus the modal value of Undiscovered Resources. In their entirety these latter are expressed as a range of values from 95% probability of occurrence to 5% probability of occurrence with calculated or estimated values of the Mode or the Mean. Cumulative Production values are not a part of Futures resource understanding.

N.B.: For reasons of simplification, analysts commonly focus on the single value expressed as the Mode or the Mean. We encourage the reader to recognize that the assessments comprise a range of values from 95% to 5% probability of occurrence. Uncertainties abound in petroleum exploration, and one should anticipate that realities of occurrence may approach the extremes-high or low.