This page is mainly about US reserves and resources, but also includes some broader North America data. The main question is the amount of gas that will ultimately be recovered.
30 Jun 2013.
US proved reserves were about 300 trillion cubic feet (Tcf) as of end 2012, according to the BP statistical review of world energy. Gas prices affect this number, but it is fairly solid. Something between 1025 Tcf and 2384 Tcf will probably be added to proved reserves over time.
”Technically recoverable resources”, TRR, is the most common concept applied in estimating total remaining gas that exists in addition to proved reserves. There are two fairly comprehensive estimates for US TRR, in addition to proved reserves: 1025 Tcf (2011 estimate, USGS), and 2384 Tcf (2012 estimate, Natural Gas Committee).
Different sources have somewhat differing definitions for TRR, and details are rarely given. The USGS aims to estimate what will be added to proved reserves in 30 years, so probably this is a conservative estimate. It is also rather out of date, so can be taken as a lower bound. The Natural Gas Committee estimate does not include economic considerations, and so is probably high.
Basic background (3 Feb 2010)
BP annual statistical summary (Jun 2013) Proved reserves as of 2012, 300 Tcf.
From table of proved reserves, main entries in TCM, (Tcf in parenthesis).
|North America||10.8 (383)||12.1 years|
|US||8.5 (300)||12.5 years|
|World||187 (6614)||55.7 years|
Potential gas committee (9 Apr 2013) Technically recoverable resources, in addition to proved reserves, as of end 2012, 2384 Tcf; with reserves, 2688 Tcf.
Unconventional gas background (30 Jan 2010) The core definition of unconventional gas (sometimes called continuous) is that the gas is highly dispersed in the rock, rather than in a concentrated bubble over oil or water. The main types of unconventional gas are deposits in shale (“shale gas”), in sandstone (“tight gas”), in coal (“coalbed methane”), or in ice (“gas hydrates”).
Mining of unconventional gas is relatively new. It began with tight gas and coalbed methane in the 1980s and 90s, and has recently expanded into shale. The main enabling technologies are horizontal drilling and hydraulic fracturing, both aimed at connecting a large volume of fractured rock to the well.
Because the area is so new, there remain significant unknowns. The first is that the environmental impact, especially contamination of aquifers, is not well characterized. The second is that the long term productivity of wells, and hence the cost and size of ultimate recovery volumes, is unclear.
USGS National Oil and Gas Assessment (NOGA) (21 Jun 2012) Estimate of undiscovered, technically recoverable resources, as of 2011, 1025 Tcf.
The main comprehensive, regularly updated, public source is the BP Statistical Review of World Energy
Natural gas reserves for a higher level view.
May 2005. Paper on USGS web site.
“U.S. Geological Survey Assessment Concepts for Continuous Petroleum Accumulations. By James W. Schmoker”
“A continuous accumulation is envisioned as a collection of petroleum-charged cells. Cell-level production data, from the accumulation being assessed or an analog accumulation, are the foundation for forecasts of potential additions to reserves. In effect, production data are used to empirically provide the product of petroleum-in-place and recovery factor. …
The U.S. Geological Survey (USGS) periodically conducts assessments of the recoverable oil and natural gas resources of areas within the United States and also in other regions of the world. The purpose of these assessments is to develop geology-based, well-documented estimates of quantities of petroleum having the potential to be added to reserves within some future time frame. For the National Oil and Gas Assessment (NOGA) series begun by the USGS in 2000, the future time frame—the forecast span—is 30 years. …
FORSPAN is the model used to assess potential additions to reserves in continuous accumulations as part of the ongoing NOGA series of domestic petroleum assessments. …
Continuous petroleum accumulations form a geologically diverse group that includes coalbed methane, “tight” gas, basin-center gas, oil and gas in fractured shale and chalk, gas hydrates, and shallow biogenic gas. Despite their obvious differences, these various petroleum deposits are linked together as continuous accumulations by two key geologic characteristics: (1) they consist of large volumes of rock pervasively charged with oil or gas, and (2) they do not depend upon the buoyancy of oil or gas in water for their existence. …
The ultimate resource base is enormous. However, in order for USGS resource assessments to be of near-term relevance to the society that funds them, the assessment scope needs to be constrained from that of crustal abundance to resources that might be recoverable in the foreseeable future. Such constraint is supplied by limiting assessments of continuous accumulations to those quantities of oil and gas having the potential to be added to reserves within some specified forecast span …
assessment approach is based on the production performance of continuous petroleum reservoirs, as empirically shown by wells. … Such reservoir-performance assessment models are particularly well suited to continuous accumulations that are already partially developed. The wells themselves serve as comprehensive analog computers that evaluate and weight all relevant reservoir parameters. Lacking sufficient drilling and production data, the assessor must draw upon information from analog accumulations. …
In many cases, most of the untested cells having potential for additions to reserves within 30 years will be localized in areas (sweet spots) where production characteristics are relatively favorable. One or more sweet spots may already be known to exist. An important component of the assessment is to postulate, on the basis of geologic understanding and principles of petroleum engineering, the presence or absence of additional sweet spots. …
The uncertainties associated with the variables required for an assessment of a continuous accumulation are considerable, leading to a substantial range of possible input values. Many of the variables that make up the set of input data are therefore represented by probability distributions rather than by single (point) values. Resource forecasts derived from these input data are also represented by probability distributions. …
Technically Recoverable Resources Versus Potential Additions to Reserves
In the 1995 National Assessment, the fundamental petroleum quantity assessed was technically recoverable resources. These were defined as resources producible using current recovery technology but without reference to economic profitability (U.S. Geological Survey National Oil and Gas Resource Assessment Team, 1995).
However, given the sophistication of current petroleum- related technology, essentially all of the moveable oil or gas in almost any accumulation that can be envisioned has become recoverable from a purely technical standpoint. In the FORSPAN resource-assessment model for continuous accu- mulations, more restrictive conditions are imposed, to the extent that assessed petroleum volumes must not only be tech- nically recoverable but must also have the potential to be added to reserves.”
Oct 2008. USGS assessment fact sheet.
“Assessment of Gas Hydrate Resources on the North Slope, Alaska, 2008”
“The U.S. Geological Survey (USGS) recently completed the first assessment of the undiscovered technically recoverable gas-hydrate resources on the North Slope of Alaska. Using a geology-based assessment methodology, the USGS estimates that there are about 85 trillion cubic feet (TCF) of undiscovered, technically recoverable gas resources within gas hydrates in northern Alaska. …
Approximately 35 years ago, Russian scientists made what was then a bold assertion that gas hydrates, long a curiosity of physical chemists, should occur in nature. Since then, the USGS and others have built a strong scientific foundation supporting the conclusion that gas hydrates are a global phenomenon containing potentially huge volumes of gas in terrestrial polar regions and the deep water portions of most continental margins. Gas hydrates are naturally occurring, ice-like solids in which water molecules trap gas molecules in a cage-like structure known as a clathrate. Although many gases form hydrates in nature, methane hydrate is by far the most common. …
[Table has amounts labeled F95, F50, F5; text says,] the USGS estimates that the total undiscovered natural gas resources in gas hydrate range between 25.2 and 157.8 trillion cubic feet (TCF; 95-percent and 5-percent probabilities of greater than these amounts, respectively), with a mean estimate of 85.4 TCF.”
Dec 2008. Navigation: USGS, National Oil and Gas Assessment, Assessment updates, Comprehensive resource summary.
“The main objective of the National Assessment of Oil and Gas Project is to assess the potential for undiscovered oil and natural gas resources of the onshore United States. The last comprehensive National Assessment was completed by the USGS in 1995, and since 2000 the USGS has been re-assessing basins of the U.S. that are considered to be priorities for oil and gas resources rather than assessing all of the basins of the U.S. The maps ands tables accompanying this introduction represent the update to the National Assessment as of the end of December, 2006. Since 2000, the USGS has re-assessed 22 priority basins, and has plans to re-assess 10 more basins. These 32 basins represent about 97% of the discovered and undiscovered oil and gas resources of the United States. As each basin is re-assessed the assessment results are added to the tables, and these new values replace the assessment results from 1995. New assessments completed in 2006 include Alaska North Slope coalbed methane, the Sacramento Basin, the Eastern Oregon-Washington Province, and the conventional oil and gas resources of the Powder River Basin.”
“USGS NATIONAL ASSESSMENT OF OIL AND GAS RESOURCES UPDATE (December, 2008) CONVENTIONAL OIL AND GAS RESOURCES”
[The tabular summary gives an estimate of resources in each of about 70 “provinces”. Only a few are updated each year. Those updated for 2008 included:
(so no update for the TX and OK shale plays)
In each province, an “F05”, an “F95” estimate, (amount is great than the given estimate with 5% and 95% confidence; see Alaska hydrate entry) and a mean estimate (not just the average of the F05 and F95) are given. The means are summed, to give a total.
Totals of means:
By analogy with the Oct 2008 entry, “resources” probably means “technically recoverable resources”.]
18 Jun 2009. Colorado School of Mines website.
“POTENTIAL GAS COMMITTEE REPORTS UNPRECEDENTED INCREASE IN MAGNITUDE OF U.S. NATURAL GAS RESOURCE BASE”
“The Potential Gas Committee (PGC) today released the results of its latest biennial assessment of the nation’s natural gas resources, which indicates that the United States possesses a total resource base of 1,836 trillion cubic feet (Tcf). … Most of the increase from the previous assessment arose from reevaluation of shale-gas plays in the Appalachian basin and in the Mid-Continent, Gulf Coast and Rocky Mountain areas. …
Dr. John B. Curtis, Professor of Geology and Geological Engineering at the Colorado School of Mines and Director of the Potential Gas Agency … cautioned, however, that the current assessment assumes neither a time schedule nor a specific market price for the discovery and production of future gas supply. “Estimates of the Potential Gas Committee are ‘base-line estimates’ in that they attempt to provide a reasonable appraisal of what we consider to be the ‘technically recoverable’ gas resource potential of the United States,” he explained. …
When the PGC’s results are combined with the U.S. Department of Energy's latest available determination of proved gas reserves, 238 Tcf as of year-end 2007, the United States has a total available future supply of 2,074 Tcf, an increase of 542 Tcf over the previous evaluation. …
The growing importance of shale gas is substantiated by the fact that, of the 1,836 Tcf of total potential resources, shale gas accounts for 616 Tcf (33%). …
Details of the Potential Gas Committee’s Natural Gas Resource Assessment (as of December 31, 2008)
The Potential Gas Committee (PGC) reports its gas resource assessments biennially in three categories of decreasing certainty—Probable, Possible and Speculative. For each category, a minimum, most likely and maximum volume is assessed for each of 89 geological provinces in the Lower 48 States and Alaska. The mean values shown in Table 1 below were calculated by statistical aggregation of the minimum, most likely and maximum traditional values for each resource category. Mean values for total traditional resources and total coalbed gas resources are aggregated separately. This procedure imparts greater statistical validity to the results and allows for more direct comparison of PGC’s assessments with those made by other organizations. …
[The following is a subset of the table in the press release]
Resources Category 2008 Mean Values, Tcf Traditional Gas Resources: Probable resources (current fields) 441.4 Possible resources (new fields) 736.9 Speculative resources (frontier) 500.7 Subtotal Traditional Resources* 1,673.4 Coalbed Natural Gas: Probable resources 14.2 Possible resources 49.8 Speculative resources 98.9 Subtotal Coalbed Gas Resources* 163.0 Total Potential Resources 1,836.4 Proved reserves (DOE/EIA) 237.7** U.S. Future Supply 2,074.1 * Mean values for Probable, Possible and Speculative resources are not arithmetically additive in deriving the subtotal. Subtotal mean values are additive in deriving Total Potential Resources. ** Latest available figure is for year-end 2007. Note: Totals are subject to rounding and differences due to statistical aggregation of distributions.
… The cost of the printed report is US$495 …
About the Potential Gas Committee
The Potential Gas Committee, an incorporated, nonprofit organization, consists of knowledgeable and highly experienced volunteer members who work in the natural gas exploration, production and transportation industries and in the field and technical services and consulting sectors. The Committee also benefits from the input of respected technical advisors and various observers from federal and state government agencies, academia, and industry and research organizations in both the United States and Canada. Although the PGC functions independently, the Potential Gas Agency at the Colorado School of Mines provides the Committee with guidance, technical assistance, training and administrative support, and assists in member recruitment and outreach. The Potential Gas Agency receives financial support from prominent E&P and gas pipeline companies and distributors, as well as industry trade and research organizations and unaffiliated individuals.”
Jun 2009. BP website; prominent link on home page.
“Statistical Review of World Energy 2009”
“Notes: Proved reserves of natural gas– Generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and operating conditions.”
From table of proved reserves, tn of cubic meters (*35.31 to get tn cubic feet).
|North America||9.51||7.24||8.88||8.87 (313.1)||10.9|
Annual percent growth in world proved reserves (CAGR when for multiple years)
29 Oct 2009. EIA website.
“U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves Report, 2008”
“Proved reserves are those volumes of oil and natural gas that geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions. Proved reserves of natural gas rose enough not only to replace production, but also to grow by almost 3 percent over 2007, largely due to continued development of unconventional gas from shales … Under Securities and Exchange Commission (SEC) rules for determining reserves that have been in effect since 1982, operators assessed their 2008 reserves based on what they could produce with reasonable certainty at the market price on the last day of the year. Under updated SEC rules issued in 2008 that take effect in 2010, operators will instead use an average of first-day-of-the-month prices throughout the year, which is less sensitive to volatility in prices, in developing their reserves estimates. …
Net revisions of natural gas proved reserves for 2008 were a negative 3.1 Tcf, reflecting a significant drop in the price used to estimate the economic viability of reserves from 2007 to 2008. Under existing SEC rules, the price at Henry Hub, Louisiana used to estimate reserves dropped 21 percent from $7.11 to $5.63 per million British thermal units (MMBtu) from year-end 2007 to year-end 2008. Under the rules that will be in effect for the 2009 reporting year, the Henry Hub price would have increased 32% from $6.76 to $8.93 per MMBtu. The net revisons estimate consists of a balance between two much larger numbers: negative revisions of 33.8 Tcf largely due to low end-of-year natural gas prices and positive revisions of 30.7 Tcf, largely the result of improving ability to produce unconventional gas economically. …
Production. Natural gas produced during a year is subtracted from proved reserves. EIA's Annual Survey of Domestic Oil and Gas Reserves includes an estimate of production, based on interim estimates from operators. As reported on the survey, production of dry natural gas in 2008 totaled 20.5 Tcf in 2008, up 5.4 percent from 2007, marking the third consecutive annual increase in U.S. natural gas production. This is similar to EIA's official reported estimate of natural gas production derived from final producer reports.
The Importance of Unconventional Sources. Application of new technologies can convert categories of previously uneconomic natural gas resources into proved reserves. In the 1990s, coalbed methane led this reserves growth. Today, increases in shale gas proved reserves reflect the industry's rapidly maturing ability to apply two technologies to shale formations: horizontal drilling and hydraulic fracturing. EIA began reporting reserves data separately for coalbed methane in 1990 and for shale gas in 2008. EIA does not currently report reserves estimates for tight gas, the third category of gas generally described as unconventional.
In 2008, dry natural gas proved reserves attributable to shale reservoirs grew dramatically, up 51 percent to a total of 32.8 Tcf, or 13 percent of total proved reserves of dry natural gas (Table 2). Of this, 8.9 Tcf was from discoveries and 4.2 Tcf was from upward revisions and other adjustments. Production from shale formations reported on the reserves survey climbed sharply as well, surpassing 2 Tcf in 2008; a 65 percent increase from 2007. …
[The following is a subset of the table in the report. “Res” is Proved Reserves at year end. “Disc” is Discoveries. “Rev” is Revisions. “Prod” is Production.]
Table 2: Changes to Proved Reserves of Dry Natural Gas by Source (Trillion Cubic Feet at 14.73 psia and 60 degrees Fahrenheit) Source Res. 2007 Disc. 2008 Rev. 2008 Prod. 2008 Res. 2008 Shale 21.7 8.9 4.2 -2.0 32.8 TOTAL 237.7 29.5 -2.0 -20.5 244.7
Natural Gas Liquids. EIA also collects reserves estimates of natural gas liquids (NGL) which are hydrocarbons in natural gas that are extracted (as liquids) at the surface in gas processing or cycling plants. Generally, such liquids consist of propane and heavier hydrocarbons and are commonly referred to as lease condensate, natural gasoline, and liquefied petroleum gases. Natural gas liquids include natural gas plant liquids (primarily ethane, propane, butane, and isobutane) and lease condensate (primarily pentanes produced from natural gas at lease separators and field facilities). Year-end 2008 proved reserves of NGL were 9.3 billion barrels, an increase of 1.4 percent over 2007”
12 Dec 2009. Presentation at the United Nations Climate Change Conference in Copenhangen.
“Worldwide Gas Shales and Unconventional Gas: A Status Report. Vello A. Kuuskraa, Scott H. Stevens, ADVANCED RESOURCES INTERNATIONAL, INC.”
“We have completed basin-level assessments of the “Magnificent Seven” North American gas shales which dominate activity.
|Gas Shale Basins||Resource Endowment||Recoverable Resource|
|U.S. (5 basins)||3760 TCF, 107 TCM||475 TCF, 13 TCM|
|Canada (2 basins)||1,380 TCF, 39 TCM||240 TCF, 7 TCM|
The resource endowment for these “Magnificent Seven” gas shales of 146 Tcm (5,140 Tcf) already exceeds Rogner’s (1997) estimate for all of North American gas shale of 109 Tcm (3,840 Tcf).
The numerous still to be defined and smaller gas shale plays in the U.S. (e.g., Antrim, Huron, Eagleford) and in Canada (e.g., Liard, Cordova and Utica) will add to these totals.”
[In another publication, Advanced Resources use “recoverable” and “technically recoverable” synonymously.]
Jun 2010. BP website; prominent link on home page
|North America||9.52||7.32||9.18||9.16 (323.4)||11.3|
30 Nov 2010. EIA website.
“Summary: U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Proved Reserves 2009”
“Domestic proved reserves1 of oil and natural gas increased significantly in 2009. U.S. natural gas proved reserves—estimated as “wet” gas which includes natural gas plant liquids—increased by 11 percent in 2009 to 284 trillion cubic feet (Tcf).”
Apr 2011. Potential Gas Committee
Total resource is divided into recoverable and unrecoverable. Recoverable is divided into cumulative production, proved reserves, probable resources, possible resources, and speculative resources. The latter three, the resource categories, are now estimated at 508 Tcf, 611 Tcf, 512 Tcf, summing to 1,631 Tcf.
August 2011. USGS National Oil and Gas Assessment
“Total mean undiscovered gas resources (undiscovered technically recoverable resources)”
“Mean total: 1,025 Tcf”
[See Dec 2008 entry for more background on the USGS goal and approach.]
9 Apr 2013. Potential Gas Committee press release.
http://potentialgas.org/press-release (not a permalink)
“POTENTIAL GAS COMMITTEE REPORTS SIGNIFICANT INCREASE IN MAGNITUDE OF U.S. NATURAL GAS RESOURCE BASE”
“The Potential Gas Committee (PGC) today released the results of its latest biennial assessment of the nation’s natural gas resources, which indicates that the United States possesses a total technically recoverable resource base of 2,384 trillion cubic feet (Tcf) as of year-end 2012. …
in addition to 49 Tcf of domestic marketed-gas production estimated for the two-year period since the Committee’s previous assessment. …
When the PGC’s assessments of technically recoverable resources are combined with the U.S. Department of Energy’s latest available determination of proved reserves, 305 Tcf (dry gas) as of year-end 2010, the United States has a total available Future Supply of 2,688 Tcf”