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Abstract In 1980, the National Petroleum Council (NPC)/ published the most authoritative and comprehensive estimates to date of the technical and economic potential of tight sands gas. While the NPC study remains the landmark effort on this subject, its estimates for recoverable natural gas are considered by many to be optimistic. The Gas Research Institute (GRI) and the Department of Energy (DOE) jointly commissioned construction of the Tight Gas Analysis System (TGAS) as a vehicle to perform systematic sensitivity analyses of the NPC study, to serve as a repository for future additions to the data base and analytical understandings of the technology, and to estimate the benefits of specified R and D advances. This paper describes TGAS briefly demonstrates its reconciliation with published NPC results, and reports sensitivity analyses of:Improved fracture effectiveness with and without closer well spacing; Producing from gas-bearing lenses encountered by the wellbore versus lenses lying remote from the wellbore; and Altering the NPC's assumptions about the relationship between reservoir permeability and thickness. The reconciliation and sensitivity studies confirm the analytical integrity of the NPC study but also point out that the NPC's results contain significant uncertainties. Background and Purpose Low permeability (" tight") natural gas sands were recognized as a major potential domestic resource by the middle 1960's. The detailed studies of the late 1970's, and particularly the 1980 National Petroleum Council study particularly the 1980 National Petroleum Council study brought this resource to national attention. This highly credible study concluded that natural gas from tight sands was a massive resource with substantial potential for sustaining domestic gas production in an era of declining conventional gas reserves-to-production ratios and could conceivably contribute to a "gas economy" in the near- and mid-term. The NPC results, while highly respected, were considerably higher than prior estimates. A number of uncertainties (requiring sensitivity analyses) are inherent in the NPC results. Thus, the Gas Research Institute and the U.S. Department of Energy jointly sponsored the "automation" of the NPC study in order to:Explore the sensitivity of its geological, technological, and economic assumptions on the overall estimates; Test the implications of alternative gas research strategies on the resultant economically and technically producible gas; and Serve as an analytically useful repository for new and emerging findings about the resource and the technology for characterizing and extracting it. The resulting system, christened the Tight Gas Analysis System (TGAS), has been constructed, validated against the NPC results, and exercised through selected sensitivity analyses. This paper seeks to quantify some of the uncertainties in the NPC estimates in order to establish which are critical areas for further research and/or analyses. It does not challenge the NPC estimates, findings, or conclusions โ only new data can do that. It does however, explore the implications of key uncertainties in a "what ifโฆ" fashion. P. 299
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.86)
- North America > United States > Texas > Permian Basin > Val Verde Basin (0.99)
- North America > United States > Texas > East Texas Salt Basin > Cotton Valley Group Formation > Cotton Valley Sand Formation (0.99)
- North America > United States > New Mexico > Permian Basin > Val Verde Basin (0.99)
- (3 more...)
Members SPE-AIME The paper was presented at the SPE/DOE Unconventional Gas Recovery Symposium of the Society of Petroleum Engineers held in Pittsburgh, PA, May 16โ18, 1982. The material is subject to correction PA, May 16โ18, 1982. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words Write: 6200 N. Central Expwy., Dallas, TX 75206. Abstract In the near future, the majority of America's natural gas supply will be produced from three principal resources: conventional, deep (more principal resources: conventional, deep (more than feet), 15,000 and tight (less than 0.1 md) gas reservoirs. These differ from one another in terms of: * Risks โโ especially in technologies fordiagnosing and stimulating deep and tight reservoirs; and * Gas prices โโ under NGPA, deep gas is deregulated and tight gas receives anincentive price, but is not deregulated. This paper compares the overall present value economics of the three resources in light of these above factors. The analysis shows that, while extraction costs are lower for conventional gas, larger new field discoveries for "frontier" deep and tight gas may make them competitive when full-field economics is considered. This conclusion is even stronger if either differential incentive prices are continued or the technological risks prices are continued or the technological risks affecting the deep and tight resources are reduced. To the extent this competition between conventional, deep, and tight gas can be fostered, the productivity of exploration (reserves added per foot) and overall gas reserves will be per foot) and overall gas reserves will be improved. Introduction Historically, natural gas has been a cheap and abundant fuel, produced from large fields of "conventional" wells at relatively shallow depths. However, drilling for conventional gas appears to be reaching a point of diminishing returns: * The finding rate (amount of reserves addedper foot of drilling) for new fields declined from 111 Mcf/ft during 1969-1974to 38 Mcf/ft during 1974โ1979. * The rate of discovery of fields of"significant" size has declinedexponentially from 1951 through 1975. * In 1979, exploratory success rate for newfield wildcats was stabilized at about 20%and exploratory gas wells were deeper than in any prior year. In brief, maintenance of the conventional gas reserve base requires ever increasing efforts and higher costs. These characteristics are consistent with the interpretation that the domestic conventional gas resource is relatively mature. Nehring has demonstrated that rate of discovery in mature areas generally declines to a relatively constant level, and that large and "giant" fields are discovered early in the life of the resource. Exploratory success rates are generally lower later in the life of the resource because, quite simply, larger fields are easier to find than small fields. If natural gas is to continue to meet a large portion of America's energy needs, new supplies portion of America's energy needs, new supplies must be found. Two other types of gas resources have significant potential to add large quantities of reserves: deep gas and tight gas. Significantly higher extraction costs and technical risks have deterred industry's pursuit of these resources. By contrast to the mature status of conventional natural gas, these resources are in an immature, or "frontier," stage of exploration. P. 611
- North America > United States > Colorado (0.46)
- North America > United States > Texas > Dallas County > Dallas (0.24)
- North America > United States > Pennsylvania > Allegheny County > Pittsburgh (0.24)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.69)
- North America > United States > Colorado > Piceance Basin > Williams Fork Formation (0.99)
- North America > United States > Texas > Anadarko Basin (0.94)
- North America > United States > Oklahoma > Anadarko Basin (0.94)
- (2 more...)
The paper was presented at the SPE/DOE Unconventional Gas Recovery Symposium of the Society of Petroleum Engineers held in Pittsburgh, PA, May 16-18, 1982. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Write: 6200 N. Central Expwy., Dallas, TX 75206. Introduction and Summary Low permeability gas reservoirs ("tight gas sands") are abundant in the U.S. Economic recovery of the gas in these formations requires reservoir stimulation, usually massive hydraulic fracturing. Significant investigations of tight gas sands by the National Petroleum Council (NPC), Lewin and Associates, and the Gas Research Institute (GRI) have agreed that, although some formations can be profitably produced with existing technology, improved reservoir diagnostic and stimulation techniques are required to realize the full potential of the resource. Most major operators and well-service companies conduct research and development to improve tight gas technology. A survey of tight gas research managers in eight companies was conducted to determine their R and D priorities and the constraints under which they operate. The responses of the R and D managers shooed a high degree of consensus on tight gas R and D objectives, company priorities, decision making criteria, current activities, and constraints. The representatives of six operating and two service companies stated that they prefer R and D that produces high "payoffs" in the near term, with low-to-medium risk of R and D failure. This characteristic leads industry to focus current R and D on measurement and prediction of fracture geometry (shape and orientation), particularly in the lower-risk blanket-type (as opposed to lens-type or particularly in the lower-risk blanket-type (as opposed to lens-type or lenticular) formations. Despite the presence of price incentives for production of tight gas and the potential of high return, the constraints production of tight gas and the potential of high return, the constraints on available personnel and funds for R and D limit industry's willingness to conduct the long-term, high-risk R and D needed to produce the lenticular resource. The industry R and D personnel interviewed were familiar with, and generally endorse, those long-range and high-risk objectives and priorities of the Federal tight gas research program that complement university and industry efforts. This report presents the survey results in three areas:tight gas R and D objectives and priorities; economic and organizational decision making criteria; and industry attitude toward the Federal tight gas R and D program. The companies interviewed were selected to represent both operators and service companies active in tight gas R and D. Confidentiality of survey respondents is assured by aggregation of their answers. No respondents are identified by name or distinguishing characteristics. The Tight Gas Potential and the Need for Research Tight gas is that natural gas found in low permeability (usually less than 0.1 md) formations primarily in the Southwestern and Rocky Mountain regions. These formations may be classified as either the continuous, blanket-type (formed by marine deposits) or the discontinuous, lenticular-type (formed by fluvial deposits). Due to their low natural production rates, tight gas reservoirs have not usually been economically production rates, tight gas reservoirs have not usually been economically producible without some form of stimulation to increase flow. This producible without some form of stimulation to increase flow. This stimulation technology, predominantly hydraulic fracturing, has made tight gas an increasingly attractive energy source. Much of the tight gas resource, however, remains uneconomical to produce. A substantial amount of research is still required to better produce. A substantial amount of research is still required to better understand, predict and, possibly, control those factors that influence flow rates. This includes improvements in technologies for measurement of reservoir properties, prediction of response to alternative fracture designs, creation and propping of fractures, and evaluation of the created fracture. Much of this technology is now economically applicable to the more favorable of the blanket formations. p. 171
- North America > Canada > British Columbia (0.25)
- North America > Canada > Alberta (0.25)
- North America > United States > Texas > Dallas County > Dallas (0.24)
- North America > United States > Pennsylvania > Allegheny County > Pittsburgh (0.24)