Forecasting World Natural Gas Supply - OnePetro

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Fo recasting World Natural Gas Supply S.M. Al-Fattah, SPE, and R.A. Startzman, SPE, Texas A&M U.

Summary World gas supply forecasting has proved difficult because its exploration, transportation, and customer bases depend so heavily on fluctuating economic factors. Our recent study showed that the conventional Hubbert model with one complete production cycle is not appropriate to use to forecast gas-production trends for most gas-producing countries. This paper presents our forecast for the world’s supply of conventional natural gas to Year 2050. We developed a “multicyclic Hubbert” approach that accurately models the gas-production history of each gas-producing country. Models for all countries were then used to forecast future production of natural gas worldwide. We present the multicyclic modeling approach in a convenient form that makes production data that exhibit two or more cycles easier to model and aggregated these models to regional and world levels. We also developed and analyzed supply models for some organizations [e.g., the Organization of Petroleum Exporting Countries (OPEC), the Organization for Economic Cooperation and Development (OECD), the European Union (EU), and the Intl. Energy Agency (IEA)]. Our results indicate that the world supply of natural gas will peak with a plateau production of 99 Tcf/yr from 2014 to 2017, followed by an annual depletion rate of 1%/yr. Regional analyses indicate that gas production of some regions will peak soon and that North American gas production is now (1999) at its peak. West European gas production is predicted to peak in 2002. Former Soviet Union (FSU) and Middle East countries, which contain approximately 60% of the world’s ultimate recoverable natural gas, will be the main sources of supply in the future. Introduction Natural gas is becoming an increasingly important source of the world’s energy. In recent years, natural gas use has grown the fastest of all the fossil fuels, and it will continue to grow rapidly for several decades. The U.S. Energy Information Admin. (EIA)1 reported that world gas consumption grows by 3.3%/yr compared with 2.2%/yr for oil and 2.1%/yr for coal. This higher growth rate can be attributed to several factors. First, natural gas, including unconventional gas, is available in abundant quantities in many parts of the world. Second, natural gas is environmentally cleaner than coal and crude oil. Third, the lower price of gas relative to other fuels makes it attractive to many gas operators and consumers. Fig. 1 shows the U.S. wellhead prices of gas and crude oil since 1949. These data are wellhead inflation-adjusted Copyright 2000 Society of Petroleum Engineers This paper (SPE 62580) was revised for publication from paper 59798, originally presented at the 2000 SPE/CERI Gas Technology Symposium held in Calgary. Original manuscript received 14 January 2000. This paper has not been peer reviewed.

prices based on 1992 U.S. dollars on an equivalent-energy basis. The figure shows that a somewhat direct relationship exists between oil and gas prices, with a time lag of 3 to 4 years. In 1949, the gas/oil price ratio was 0.12, indicating that gas was 12% as valuable as oil on an energy basis. Since that time, the trend of this ratio has been generally upward, reaching a value of 0.94 in 1998, indicating that gas has now reached a close price parity with oil. The gas industry is influenced by political events, economic factors, and its relationship with the oil industry. Fig. 2 shows the U.S. marketed-gas production rate since 1918. The gas-production trend from 1918 to 1970 shows exponential growth. From 1970 to 1973, gas production continued to increase but at a slower rate. Oil production peaked in 1970. Contributing factors to the slowdown in gas-rate increases might have been the oil-production decline, which resulted in a decline of associated gas production and lower gas prices. However, gas-supply shortages occurred during the very cold winter of 1972–73. Actual gas production peaked in 1973, when OPEC cut production of crude oil. Then, gas-production rates dropped, paralleling the decline in oil production. This drop in gas rate extended to 1975 because the gas market was based on long-term gas-sales contracts with stable prices. During 1975–79, gas production showed slow growth and gas prices became more extensively regulated. In 1979, the Iranian revolution caused oil prices to increase sharply, reaching a peak in 1981. This corresponded to an increase of gas prices, which peaked in 1984 (Fig. 1). The oil/gas price time lag of 3 to 4 years possibly resulted from the moderating effect of long-term gas contracts. In 1981, with low gas demand, the “gas bubble” (time period of high gas reserves and production capacity and low demand) and gas production decreased rapidly until 1986, despite the fact that gas reserves and production capacities were high. Since 1986, gas production increased steadily for a variety of reasons, including government policy and tax incentives, increased gas demand caused by fuel switching and low gas prices, and increases in unconventional gas production.2 Of considerable interest to both producers and consumers is the future direction of U.S gas production. Our recent study3 indicated that Hubbert’s model,4-7 which proved useful for oil-production forecasting, does not account for fluctuations in gas-producing rates. Thus, it may not be appropriate for forecasting gas production for the U.S. and a number of other countries. This paper presents new forecasting models for the future gas supply. Our supply models are based on country-by-country production analyses. We also discuss natural gas supply analysis by region and by organization or group.

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Fig. 1—U.S. gas and oil wellhead inflation-adjusted prices and gas/oil price ratio, 1949–98 (all on equivalent-Btu basis).

Fig. 2—U.S. natural gas and crude oil production (vertical scale on equivalent-Btu basis).

Approach Several authors4-12 showed that Hubbert’s model, with one complete production cycle, is adequate for predicting crude oil production. However, our recent study3 showed that, in the case of natural gas production, most countries exhibit two or more Hubbert-type production cycles. These additional cycles apparently result from new exploration areas and technology, regulations, economic factors, and/or political events. Using a Hubbert model with a single production cycle does not allow for these factors. To account for additional production cycles, we used the multicyclic Hubbert model described in Ref. 3. On the basis of the number of cycles suggested by the production data, we can add a number of Hubbert-type production cycles. The production rate of the multicyclic model can be computed with

The multicyclic model proved to be an effective approach to modeling cyclic production data. The following are some characteristics of the model. • It is derived from physical and mathematical concepts. • It can history match with good accuracy data fluctuations influenced by economic factors and/or political events. • The results are reproducible. • It uses obtainable historical data. • These procedures are simple and can be readily implemented with a computer spreadsheet program. • The predictions can be updated easily with new data. However, like Hubbert’s original model, the results from the multicyclic model are not unique because the model is data sensitive, especially when few data from small fields are used. Therefore, we recommend performing sensitivity analyses of model parameters. Use of many data points from large fields helps reduce model sensitivity.

, , . . . . . . . . . . .(1)

Data Sources We used historical natural gas production data from Refs. 13 through 17, U.S. gas-discovery data (1900–97) from Refs. 17 and 18, and U.S. marketed-gas production

where n=total number of production cycles, qmax=maximum or peak production, tmax=time at peak production, and a=constant. Eq. 1 has fewer parameters (three) than the Hubbert equation (which has four), making production data easier to model. Eq. 1 also provides a better fit for multicyclic production data than the Hubbert model with its single production cycle. The parameters of the multicyclic model can be determined with a nonlinear least-squares method. Total ultimate recovery, Gpa or Gpa,u, is then determined by adding the ultimate recoveries for each production cycle. .

3,500 3,000 2,500 2,000 1,500

. . . . . . . . . . . . . . . . . . . . . . . . . .(2)

1,000

Future recoverable gas is obtained by subtracting cumulative production from ultimate recovery. The “logistic” curve of the cumulative production of the multicyclic model can be calculated as

500

.

. . . . . . . . . .(3)

0 North South and Western Eastern America Central Europe Europe America and FSU

Middle East

Africa

AsiaPacific

Fig. 3—Distribution of world’s conventional gas by region: cumulative produced, future recoverable, and ultimate recovery.

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North America South and Central America Model

Fig. 4—Western Hemisphere region natural gas production models.

(1918–97) from Refs. 15 and 16. Refs. 13 and 14 provided data for annual production of natural gas for all other countries for 1971–97 and for proved reserves of natural gas for all countries. Analysis by Region This section presents analyses of world natural gas by region. The forecasting model for each region was constructed by aggregating the corresponding countries’ models to their respective region level. Fig. 3 depicts the results for ultimate recovery, future recoverable gas, and cumulative production for each region. North America. This region includes Canada, Mexico, and the U.S. Historically, most of the region’s production is from the U.S. In 1971, U.S. production of 22.5 Tcf/yr contributed approximately 88% of the region’s production compared with 72% in 1997. A 27-year (1971–97) average regional production share for the U.S. is approximately 81%. In contrast, Canada increased its share of production from approximately 10% (2.5 Tcf/yr) in 1971 to 24% (6.6 Tcf/yr) in 1997. Mexico has a fairly stable share, ranging from 3 to 4% of the total regional production during 1971–97. Fig. 4 shows the region’s actual and predicted gas production from the multicyclic Hubbert approach. The 1997 predicted production of 28.1 Tcf/yr is higher than actual production by 0.5 Tcf/yr. The model indicates that conventional gas production of this region peaks in 1999 at approximately 28.6 Tcf/yr. Production then declines at an average annual rate of 0.7 Tcf/yr from 2001 to 2027; thereafter, the decline rate slows to 0.4 Tcf/yr. Most production is predicted to come from the U.S. until 2010 when Canadian and U.S. production is the same at 10.5 Tcf/yr. Canada’s production share reaches approximately 55% by 2025 and decreases to 41% by 2040. Our studies indicated that the estimated ultimate recovery of conventional gas for this region is approximately 1,900 Tcf, with approximately 840 Tcf remaining to be produced (future recoverable gas) as of Year-End 1997. This quantity has an annual depletion rate of 3.3%/yr, the highest depletion rate of recoverable gas of any region worldwide. In particular, the U.S. has an annual depletion rate of 6.4%/yr, ranking it worldwide as the country with the 65

Eastern Europe Western Europe Model

Fig. 5—European region natural gas production models.

highest rate. Canada and Mexico have annual depletion rates of 2.0 and 0.6%/yr, respectively. South and Central America. This region includes Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Trinidad and Tobago, and Venezuela. These countries produced about 3.4% of world gas production during 1997 and hold approximately 4.4% of world proved reserves of natural gas as of Year-End 1997. The largest gas producer of this region is Venezuela, followed by Argentina, with Trinidad and Tobago coming in a far third. This same ranking holds for proved reserves. Fig. 4 shows actual and predicted gas production for the region. Our forecast model indicates that production in this region reaches a plateau of slightly less than 5 Tcf/yr and stays at this level from 2015 to 2021. Production then starts to decline steadily at an average of 0.03 Tcf/yr through 2050, representing an annual average decline rate of 0.7%/yr. The model predicts production in this region at 3.8 Tcf/yr in 2050, with 285 Tcf of cumulative gas produced by that time. Gas supply is mainly from Venezuela and Argentina until the peak production of the region is reached, after which Venezuela takes the lead. Venezuelan production is predicted to contribute 54% of the total region production in 2025 and 78% in 2050. Estimated ultimate recovery for this region is 419 Tcf, of which we predict that 68% (285 Tcf cumulative gas) will be produced by 2050. Future recoverable gas of this region is 364 Tcf, which will last for approximately 130 years, assuming a constant 1997 rate of production. The region’s annual depletion rate is 0.76%/yr; Argentina has the highest rate (2%/yr), followed by Trinidad and Tobago (1.8%/yr). Western Europe. The major producing countries from this region will continue to be The Netherlands, the U.K., and Norway. These countries contributed 80% of 1997 west European production. Norway’s share of the region’s production is predicted to increase from 15.4% in 1997 to 51% in 2015, after which it dominates the region’s production, reaching a share of 85% in 2035 and 90% in 2050. Fig. 5 shows the region’s actual and predicted production. Our model shows that peak production occurs in 2002 at 12 Tcf/yr. Production then has an annual average 65

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Fig. 6—Middle East region natural gas production model.

decline rate of 3.6%/yr until 2015. After that, production gets flatter (mainly owing to Norway’s production), then has a more relaxed annual decline rate of 2%/yr until 2050. Some countries in this region have already passed their production peaks. Austria, which had a peak in 1975 and a second smaller peak predicted to have occurred in 1998, is now in decline. France peaked in 1983 and has experienced a general decline since then. We estimated the ultimate recoverable gas for this region to be 560 Tcf. Of this amount, approximately 66% remained to be produced as of Year-End 1997 and 535 Tcf of cumulative gas is predicted to be produced by 2050. Our analysis indicates that the west European region, with an annual depletion rate of 2.8%/yr, has the secondhighest depletion rate after North America. Countries with high depletion rates are Denmark (6.3%/yr), France (5.9%/yr), Austria (5.5%/yr), and The Netherlands (5.5%/yr). With 1997 production given as constant, future recovery of gas will continue for 36 years, close to that of North America. Eastern Europe and FSU. This region includes Albania, Hungary, Romania, other low-producing countries of eastern Europe, and the FSU. As of 1997, the FSU alone accounted for 29% of the world’s gas production and held approximately 39% of the world’s proved gas reserves. In contrast, eastern European nations contribute less than 2% of world gas production and have less than 1% of the world’s proved reserves. Fig. 5 shows actual and predicted production of this region. Predicted 1997 production is slightly higher than the reported production by 0.6 Tcf/yr. Production in this region has been declining since 1990, when the countries of FSU separated and became independent. Production is predicted to stay at about the 1997 level until 1999 and to start increasing by 2000, reaching a peak in 2032 at approximately 36 Tcf/yr. Our prediction indicates a production plateau at the peak level extending from 2030 to 2035. With the exception of FSU, all eastern European countries passed their production peaks in the 1980’s. The increased gas production is expected to come mainly from the FSU, primarily from western Siberia. The FSU’s low gas-depletion rate of 0.9%/yr is far less than eastern Europe’s high depletion rate, which averages approximate-

Fig. 7—Asia Pacific and Africa regions natural gas production models.

ly 5%/yr. Estimated ultimate recovery for this region is 3,411 Tcf, with approximately 81% of this amount remaining to be produced as of Year-End 1997. By 2050, about 72% of the ultimate recovery is predicted to be produced and gas production is predicted to be 30.6 Tcf/yr, approximately the 1990 level. Middle East. This region includes Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, Syria, and the UAE among other countries. It contains 34% of the world’s proved gas reserves. The major gas-producing countries in this region are Saudi Arabia and Iran, followed by the UAE and Qatar. Political events in the region and oilrelated OPEC policies affected the region’s gas production. These include Iran’s cutback production of oil in 1979, the United Nations (UN) sanction on Libya, and the UN sanction on Iraq following its invasion of Kuwait in 1990. Fig. 6 shows the region’s actual and predicted production, indicating how effective the multicyclic approach is in accounting for such unpredictable events. Production is predicted to increase at an average annual increase of 0.6 Tcf/yr until 2040, when it peaks at 29.3 Tcf/yr. Production then declines at a low rate of approximately 0.2 Tcf/yr. By 2050, production is predicted to be 27.2 Tcf/yr, with most of it from Iran, Saudi Arabia, Qatar, and the UAE. Estimated ultimate recovery for the Middle East is 2,508 Tcf, with future recoverable gas of 2,433 Tcf remaining as of YearEnd 1997. Our work indicates that approximately 43% of this region’s future recoverable gas will be produced by 2050. Africa. The 1997 production for this region was 3.3 Tcf/yr, of which Algeria produced approximately 74%. Algeria is expected to continue to be the major producer in Africa until 2043, when Nigeria and Libya take over the role. By 2050, Nigerian, Libyan, and Algerian production shares are predicted to be 41, 29, and 17%, respectively. Fig. 7 shows actual and predicted production of the region. The figure indicates that production peaks in 2014 at 7.2 Tcf/yr, with an average annual increase of 0.24 Tcf/yr. Production then declines at an average annual of 0.17 Tcf/yr until 2043 and gets flatter thereafter with less than a 0.05-Tcf/yr average annual decline. The model shows that the 1997 production level is repeated in 2035.

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Fig. 8—Distribution of world’s conventional gas by organization/group.

Fig. 9—Natural gas production predictions for different organizations/groups and the world.

Estimated ultimate recovery for this region is 476 Tcf, and the future recoverable gas is 426 Tcf (Table 1 of Ref. 19). At 1997 production levels, remaining recoverable gas is expected to last more than 10 decades. This region model gives an annual depletion rate of 0.78%/yr, close to that of the South and Central America region.

gas production from OPEC countries peaks in 2038 at 34.9 Tcf/yr, with most production coming from Iran, Saudi Arabia, Qatar, and the UAE through the forecast period. In contrast, conventional gas production from non-OPEC countries is expected to peak by 2004 at 78.8 Tcf/yr, then decrease at an average decline of 1.1%/yr of peak production to 2050. OPEC’s future recoverable gas is estimated to be 3,055 Tcf as of Year-End 1997, with an annual depletion rate of less than 0.5%/yr. These future reserves account for approximately 39% of the world’s future recoverable gas.

Asia Pacific. Production from this region has increased steadily since 1971, except during 1982 and 1983 when Indonesia reduced its production to 44 and 20%, respectively. This had an impact despite the addition of Malaysia and Thailand’s production as first reported in 1981 and 1982, respectively. Fig. 7 shows the region’s actual and predicted production, indicating that peak production is predicted to occur in 2012 at 16.7 Tcf/yr. Production decline then takes place at an annual average of approximately 0.4 Tcf/yr (2.4%/yr). We estimate ultimate recovery of gas for this region to be about 800 Tcf, of which 86% remained to be produced as of Year-End 1997 at an annual depletion rate of 1.2%/yr. Analysis by Organization/Group We combined the country models according to their affiliated organization or group. This section presents analyses of natural gas production and outlook of gas supply for OPEC, OECD, IEA, and the EU. Figs. 8 and 9 show the results for each organization or group. Ref. 19 gives the prediction-model plots for each of these organizations. OPEC and non-OPEC. The OPEC countries hold approximately 43% (2,175 Tcf) of the world’s proved reserves of natural gas as of January 1998. Iran, Qatar, the UAE, and Saudi Arabia contribute 69% of OPEC gas proved reserves and approximately 30% of worldwide reserves. Although gas production from OPEC countries accounts for only 13% of 1997 world produced gas, its production has increased steadily since the 1970’s. Gas production increased from 2 Tcf/yr in 1971 to 10.5 Tcf/yr in 1997, or 81%. Exceptions to this continual production increase occurred in 1974 and in 1979–80, when gas production decreased with the OPEC cutback in production of crude oil in 1973 and Iran’s revolution in 1979. Fig. 9 shows actual and predicted gas production for OPEC and non-OPEC countries. The figure indicates that 69

OECD and non-OECD. Fig. 9 shows actual and predicted OECD and non-OECD gas production. The model indicates that the OECD conventional gas production peaks in 2001 at 42.2 Tcf/yr. Most of this organization’s production comes from North American countries: the U.S. and Canada. The annual OECD gas-depletion rate is approximately 3%/yr, and ultimate recoverable gas is 2,564 Tcf, with 1,300 Tcf recoverable gas remaining to be produced as of Year-End 1997. Non-OECD production is tightly controlled by the high production of the FSU. Peak production is expected to occur in 2031 at 77.4 Tcf/yr, with a relatively low gasdepletion rate of 0.65%/yr. This group’s ultimate recoverable gas is 7,480 Tcf, representing approximately 83.5% of the world’s future recoverable gas. Most future gas production from this group will come from the FSU and the Middle East gulf countries, including Iran. EU and IEA. EU gas production accounted for only 10% of the world’s produced gas in 1997, and the area holds only approximately 2% of the world’s proved reserves. Fig. 9, which shows actual and predicted EU gas production, indicates that it peaks as early as 2001 at 10 Tcf/yr. Production then declines to an insignificant amount by 2050. Among organizations and groups considered in this study, EU has the highest annual gas-depletion rate at 4.4%/yr. Ultimate gas recovery obtained from the EU model is 366 Tcf, with 193 Tcf future recoverable gas remaining as of Year-End 1997. Fig. 9 also shows the IEA gas production and forecast model. The 1997 production increases until 2001, when it peaks at 40 Tcf/yr. Production then declines steadily at an 69

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A better alternative is the annual depletion rate, which is annual production divided by remaining reserves expressed in percentage. It is a measure of how fast the reserves are being depleted each year at that year’s rate of production. Annual world-gas-depletion rate for 1997 is computed at 1%/yr. Fig. 10, which shows world-gas-depletion rate determined with the predicted rate of production and the obtained value of future recoverable gas, indicates it increases throughout the forecast period and reaches approximately 2.3%/yr by 2050.

Fig. 10—World historical and predicted annual depletion and R/P ratio of conventional gas.

annual depletion rate of 3.4%/yr. Ultimate recoverable gas obtained from the IEA model is 2,310 Tcf, of which approximately 1,100 Tcf of future gas remained to be produced as of Year-End 1997. The World World marketed-gas production increased from approximately 41 Tcf/yr in 1971 to approximately 82 Tcf/yr in 1997, a 100% increase over the 27-year period at a production growth rate of about 4%/yr. Fig. 9 shows our world conventional natural gas prediction model and indicates a very good match with the fluctuating historical production data. Predicted world production of gas in 1997 (83.8 Tcf/yr) is higher than actual production by 1.5 Tcf. The model indicates that world production of natural gas peaks between 2014 and 2017 at an approximately flat rate of 99 Tcf/yr. After the peak is passed, production starts to decline gradually and the curve gets flatter. Between 1967 and 1999, the world’s proved natural gas reserves increased substantially from about 1,043 to 5,145 Tcf, an average annual increase of 128 Tcf. Approximately 72% of the 1999 world’s proved reserves is in the FSU and the Middle East region. Our results indicate that world ultimate recovery of conventional gas is 10,000 Tcf, of which future recoverable gas is approximately 7,900 Tcf as of Year-End 1997. Tables 1 and 2 of Ref. 19 provide our results for world gas grouped by region and organization, respectively. Reserves/Production Ratio and Annual Depletion Rate The world’s gas reserves/production (R/P) ratio is 96 years, which means that world gas reserves will last for 96 years if the 1997 rate of production is constant in the future. Use of the R/P ratio as an indication of future production is misleading and meaningless because production rates probably do not remain constant over a long period of time and then drop suddenly to zero when reserves are depleted. If it is needed, an R/P curve as a function of time (or as a function of production rate) can be constructed with predicted production rate with a given estimated ultimate recovery, Gpa,u, value (Fig. 10). As an example, at Year 2030, the world’s remaining gas reserves would last for approximately 50 years provided the predicted rate of production in 2030 remained unchanged.

Conclusions We presented our analyses of the future of the world’s conventional natural gas by region and organization/group. Production data from several gas-producing countries or regions showed fluctuations. These data were affected by the relationship between the gas and oil industries, economic burdens, and governmental-policy implementations. The multicyclic model was an effective approach for modeling such production trends and developing forecasting models for them. Our analyses indicate that most industrialized countries (e.g., the U.S., Denmark, France, and the U.K.) are depleting their gas resources much faster than are developing countries. Fuel switching and gas dependence by industrial and commercial sectors and production decline of crude oil in these countries are among the reasons for the high depletion rate. This means that gas production of some regions is now in decline or will peak soon. North American gas production is predicted to have peaked in 1999 at a rate of approximately 29 Tcf/yr, and western European gas production is expected to peak in 2002 at 12 Tcf/yr. However, the FSU and the major Middle East gulf countries (Iran, Saudi Arabia, Qatar, and the UAE), which hold 68.5% of world proved reserves of natural gas, will be major sources of world gas supply with 4,880 Tcf of future recoverable gas, representing approximateJPT ly 62% of the world’s future recovery of natural gas. Nomenclature a= constant, 1/t, 1/yr Gpa= ultimate recovery of gas, L3, Tcf Gpa,u= estimated ultimate recovery, L3, Tcf n= number of production cycles qmax= peak production rate, L3/t, Tcf/yr q(t)= production rate as a function of time, L3/t, Tcf/yr Q= cumulative production, L3, Tcf t= time, t, calendar year tmax= time at peak production, t, calendar year Acknowledgment S.M. Al-Fattah thanks Saudi Aramco for supporting his PhD study at Texas A&M U. References 1.“International Energy Outlook 1998,” DOE/EIA-0484, Office of Integrated Analysis and Forecasting, U.S. Dept. of Energy, EIA, Washington, DC (April 1998). 2. Wattenbarger, R.A. and Villegas, M.E.: “Trends in U.S. Natural Gas Production,” Advances in the Economics of Energy and Resources, J.R. Moroney (ed.), J.A.I. Press, Greenwich, Connecticut (1995) 9, 169. 3. Al-Fattah, S.M. and Startzman, R.A.: “Analysis of Worldwide Natural Gas Production,” paper SPE 57463 presented at the

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1999 SPE Eastern Regional Meeting, Charleston, West Virginia, 20–22 October. 4. Hubbert, M.K.: “Nuclear Energy and Fossil Fuels,” Drill. & Prod. Prac. (1956) 17. 5. Hubbert, M.K.: “Energy Resources,” Publication 1000-D, Natl. Academy of Science/Natl. Research Council (1962). 6.Hubbert, M.K.: “Degree of Petroleum Exploration in the United States,” AAPG Bull. (11 November 1967) 51, 2207. 7. Hubbert, M.K.: “Techniques of Prediction as Applied to Production of Oil and Gas,” Proc., U.S. Dept. of Commerce Symposium, Washington, DC (June 1980) 16. 8. Ivanhoe, L.F.: “Future World Oil Supplies: There is a Finite Limit,” World Oil (October 1995) 77. 9. Campbell, C.J.: The Coming Oil Crisis, Multi-Science Publishing Co. and Petroconsultants S.A., Brentwood, U.K. (1997) 86. 10. Al-Jarri, A.S. and Startzman, R.A.: “Worldwide PetroleumLiquid Supply and Demand,” JPT (December 1997) 1329. 11. Campbell, C.J. and Laherrere, J.H.: “The End of Cheap Oil,” Scientific American (March 1998) 78. 1 2 .B a rtlett, A.A.: “An Analysis of U.S. and World Oil Production Patterns Using Hubbert-Style Curves,” Mathematical Geology (August 1999) 11. 13. Energy Statistics Sourcebook, 13th edition, OGJ energy database, PennWell Publishing Co., Tulsa, Oklahoma (1998). 14. International Energy Statistics Sourcebook, eighth edition, OGJ energy database, PennWell Publishing Co., Tulsa, Oklahoma (1998). 15. Twentieth Century Petroleum Statistics, 52nd edition, DeGolyer and MacNaughton, Dallas (1996).

16. Twentieth Century Petroleum Statistics, 54th edition, DeGolyer and MacNaughton, Dallas (1998). 17. EIA, Internet Home Page: http://www.eia.doe.gov/. 18. Attanasi, E.D. and Root, D.H.: “The Enigma of Oil and Gas Field Growth,” AAPG Bull. (March 1994) 78, 321. 19. Al-Fattah, S.M. and Startzman, R.A.: “Forecasting World Natural Gas Supply,” paper SPE 59798 presented at the 2000 SPE/CERI Gas Technology Symposium, Calgary, 3–5 April.

SI Metric Conversion Factors bbl ×1.589 873 E−01= m3 Btu ×1.055 056 E+00= kJ ft3 ×2.831 685 E−02= m3 Saud M. Al-Fattah is a PhD-degree candidate in the Petroleum Engineering Dept. at Texas A&M U., College Station, Texas, on an educational leave of absence from Saudi Arabian Oil Co. (Saudi Aramco). With Saudi Aramco since 1985, he has worked as a reservoir engineer in the Abqaiq Reservoir Management Div. and as a reservoir simulation systems analyst in the Petroleum Engineering Applications Services Dept. His specialties include reservoir engineering, operations research, economics evaluation, and strategic planning. Al-Fattah holds BS and MS degrees in petroleum engineering from King Fahd U. of Petroleum and Minerals. Richard A. Startzman is a professor in the Petroleum Engineering Dept. of Texas A&M U. in College Station. He holds a BS degree from Marietta College and MS and PhD degrees in petroleum engineering from Texas A&M U. A Distinguished Member, Startzman has published widely in the petroleum literature.

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