Browsing by Subject "coalbed methane"

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Coalbed Methane Potential of the Greater Green River, Piceance, Powder River and Raton Basins
(1991) Tyler, Roger; Ambrose, William A.; Scott, Andrew R.; Kaiser, W. R.
Coalbed methane potential of the Greater Green River, Piceance, Powder River, and Raton Basins was evaluated in the context of geologic and hydrologic characteristics identified in the San Juan Basin, the nation's leading coalbed methane producing basin. The major comparative criteria were (1) coalbed methane resources, (2) geologic and hydrologic factors that predict areas of high gas producibility and high coalbed reservoir permeability, and (3) coalbed thermal maturity. These technical criteria were expanded to include structure, depositional systems, and database and then combined with economic criteria (production, industry activity, and pipeline availability) to evaluate the coalbed methane potential of the basins. The Greater Green River and Piceance Basins have primary potential to make a significant near-term contribution to the nation's gas supply. These basins have large gas resources, high-rank coals, high gas contents, and established coalbed methane production. The Greater Green River Basin has numerous coalbed methane targets, good coal-seam permeability, and extensive hydrologic areas favorable for production. The Powder River and Raton Basins were judged to have secondary potential. Coal beds in the Powder River Basin are thermally immature and produce large volumes of water; the Raton Basin has a poor database and has no gas pipeline infrastructure. Low production and minimal industry activity further limit the near-term potential of the Raton Basin. However, if economic criteria are discounted and only major technical criteria are considered, the Greater Green River and Raton Basins are assigned primary potential. The Raton Basin's shallow, thermally mature coal beds of good permeability are attractive coalbed methane targets, but low coal-seam permeability limits the coalbed methane potential of the Piceance Basin.
Geologic and Hydrologic Assessment of Natural Gas from Coal Seams in the Measaverde Group and Fort Union Formation, Greater Green River Basin, Wyoming and Colorado
(1994) Tyler, Roger; Kaiser, W. R.; Scott, Andrew R.
The Greater Green River Basin is a fault-bounded, structurally complex intermontane basin that is subdivided into four subbasins. Face cleats strike northeast in most of the greater basin but northwest in the Sand Wash Basin to impose permeability anisotropy on the coal beds. Major coal-bearing units are the Upper Cretaceous Mesaverde Group—primarily the Rock Springs and Williams Fork Formations—and the lower Tertiary Fort Union Formation's lower coal-bearing unit. The combined net coal thickness exceeds 300 ft (91 m); individual seams are as much as 40 ft (12.2 m) thick. Coal rank ranges from subbituminous to high-volatile A bituminous, except in deeper subbasins, where rank is medium-volatile bituminous and higher. Gas contents average less than 200 scf/ton (<6.24 m3/t) at depths of less than 6,000 ft (<1,830 m). Areas of high gas content (350 to 500 scf/ton [10.92 to 15.60 m3/t]) reflect conventional trapping of migrated thermogenic and biogenic gases and correspond to areas of flow orthogonal to flow barriers, pressure transition, and convergent, upward flow of groundwater. Regionally, groundwater flows from the basin margins to discharge eventually basinward along the boundary between hydropressure and hydrocarbon overpressure and along major river valleys. Coal and coalbed methane resources are very large: 1,276 billion short tons (1.158 billion t) and 314 Tcf (8.89 Tm3), respectively. Despite huge resources, coalbed wells drilled to date have yielded little or no gas and large volumes of water, for a basinwide cumulative gas-water ratio of approximately 20 scf/bbl (~3.6 m3/m3). Deeper drilling will be required to penetrate higher rank, higher gas content coals. For example, Mesaverde gas contents between 6,000 and 7,500 ft (1,830 and 2,286 m) are approximately 350 scf/ton (~10.92 m3/t) and exceed 500 scf/ton (15.60 m3/t) below 7,500 ft (2,286 m). Deeper drilling is justified at the northwest end of the Cedar Mountain fault system in the Sand Wash Basin, along the east margin of the Washakie Basin, and around the northeast flank of the Rock Springs Uplift. In the Fort Union Formation, the Sandy Bend Arch and the Big Piney are thought to be prospective, where structural and/or stratigraphic trapping may enhance gas contents in low-rank coals.
Geologic and Hydrologic Controls Critical to Coalbed Methane Producibilty and Resource Assessment: Williams Fork Formation, Piceance Basin, NorthWest Colorado
(1996) Tyler, Roger; Scott, Andrew R.; Kaiser, W. R.
As predicted from an evolving coalbed methane producibility model, extraordinary coal gas production is precluded in the Piceance Basin by the absence of reservoir continuity and dynamic groundwater flow. The best potential for coal gas production may lie in conventional traps basinward of where outcrop and subsurface coals are in good reservoir and hydraulic communication and in areas of vertical flow potential. Synergism between tectonic and structural setting, depositional systems and coal distribution, coal rank, gas content, permeability, and hydrodynamics are controls critical to coalbed methane producibility. Within the genetically defined, coal-bearing Upper Cretaceous Williams Fork Formation, net coal thickness is typically 80 to 120 ft and is thickest in a north-south belt, behind west-east prograding shoreline sequences. Depositional setting and thrust faults cause coals along the Grand Hogback and in the subsurface to be in modest to poor reservoir and hydraulic communication, restricting meteoric groundwater recharge and flow basinward. Face cleats of Late Cretaceous age strike east-northeast and west-northwest in the southern and northern parts of the basin, respectively, normal to the Hogback thrust front. Parallelism between face-cleat strike and present-day maximum horizontal stress direction may enhance coal permeability in the north. In the Grand Valley/Parachute/Rulison and White River/Pinyon Ridge areas, structure and sandstone development control gas production from Cameo-Wheeler-Fairfield coals and/or sandstones. The most productive wells are on anticlines and structural terraces or correspond to sandstone development, reflecting fracture-enhanced permeability. Total subsurface coal resources are estimated to be 289 billion tons (262 Bt), whereas coal gas resources are approximately 99 Tcf (3.09 Tm^3), although coal gas estimates range between 80 (2.49 Tm^3) and 136 Tcf (4.24 Tm^3), depending on the calculation method. Based on completion data provided by operators, it appears that production from coalbed methane reservoirs can meet minimum economic requirements in the Grand Valley, Rulison, and Pinyon Ridge fields. To achieve high gas contents or fully gas-saturated coals for consequent high productivity in the Piceance Basin, research, exploration, and development for migrated conventionally and hydrodynamically trapped gases, in situ generated secondary biogenic gases, and solution gases will be required.
Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming
(1992) Kaiser, W. R.; Scott, Andrew R.; Hamilton, Douglas S.
Geologic and hydrologic analysis of the Upper Cretaceous Mesaverde Group shows that the major controls on the production of coalbed methane are: structural configuration, coal occurrence, gas content, hydrodynamics, and water production. Steep structural dip (500 ft/mi) and coal occurrence limit economic exploration to the eastern and southeastern margins of the basin. Coal resources occur mainly in the lower Williams Fork Formation (upper Mesaverde) in the eastern part of the basin. Most coal beds are high-volatile C to B bituminous rank and have gas contents of less than 200 scf/ton. Moreover, Williams Fork coals do not extend westward to the area of highest thermal maturity. Thus, they could not serve as conduits for long-distance migration of gas. Regionally, groundwater flows westward from an eastern recharge area across an area of low thermal maturity up the coal-rank gradient. Consequently, only a relatively small volume of gas may be available to be swept basinward for conventional trapping. The most prospective areas lie basinward, northwest of Craig, Colorado, on the upflow, downward side of a major fault zone. Gas contents in some coal beds on the downthrown side of the fault exceed 400 scf/ton. The Mesaverde is a thick, regionally interconnected aquifer system of high transmissivity, yielding large volumes of water. Paradoxically, coalbed permeabilities of 10's to 1,000's of md may be too high for economic gas production. To date, high water production and low gas content at the basin margins have limited coalbed activity in the Sand Wash Basin. Major Tertiary coal resources occur in the lower part of the Paleocene Fort Union Formation.
Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming - April 1993
(1993) Kaiser, W. R.; Scott, Andrew R.; Hamilton, Douglas S.
Large coal resources occur in the Upper Cretaceous Williams Fork Formation and lower Tertiary Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mainly subbituminous to high-volatile B bituminous and have average gas contents of less than 100 to 200 ft3/ton (<3.12 to 6.24 m3/t). Coalbed methane resources total xx Tcf (x.xx Tm3) and are xx.xx Tcf (xxx Bm3) at drilling depths of less than 6,000 ft (<1,830 m). More than 85 percent of them are in the Williams Fork. The basin's cumulative gas/water ratio is approximately 15 ft3/bbl (2.7 m3/m3). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern margins of the basin. Prospective Williams Fork and Fort Union coals, respectively, lie basinward in association with the Cedar Mountain fault system and westward along Cherokee Arch into the Powder Wash field area. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane productivity model is proposed whose essential elements are: ground-water flow through thick coals of high rank, perpendicular to no-flow boundaries and conventional trapping along them.
Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming - August 1993
(1993) Kaiser, W. R.; Scott, Andrew R.; Hamilton, Douglas S.
Coal resources occur mainly in the Upper Cretaceous Williams Fork Formation and Paleocene Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mostly subbituminous to high-volatile B bituminous rank and have average gas contents of less than 200 ft3/ton (<6.24 m3/t). Coalbed methane resources total 101 Tcf (2.86 Tm3). The basin's cumulative gas/water ratio is approximately 15 ft-1/bbl (-2.7 m3/m3). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern and southeastern margins of the basin. Prospective Williams Fork and Fort Union coals lie basinward, northwest of Craig, Colorado, in association with the Cedar Mountain fault system and westward along the Cherokee Arch, respectively. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane producibility model is proposed. High productivity is thought to require ground-water flow through coals of high gas content orthogonally toward no-flow boundaries and conventional trapping of gas along them.
Geologic and Hydrologic Controls on the Occurrence and Producibility of Coalbed Methane: Fruitland Formation, San Juan Basin
(1991) Ayers, Jr., W. B.; Kaiser, W. R.; Laubach, Stephen E. (Stephen Ernest), 1955-; Ambrose, William A.; Baumgardner, Jr., Robert W.; Scott, Andrew R.; Tyler, Roger; Yeh, Joseph S.
Coalbed methane resources in the Fruitland Formation in the San Juan Basin are estimated to be 43 to 49 trillion cubic feet at depths between 400 and 4,200 ft. The San Juan Basin leads the United States in coalbed methane production; in 1989, the basin produced approximately 65 billion cubic feet of coalbed methane. In the past 5 years, more than 1,000 coalbed methane wells have been drilled in the basin. The thickest Fruitland coal seams occur in the northern part of the basin and trend northwestward, paralleling Pictured Cliffs barrier/strandplain sandstones; in the southern part of the basin, anomalously thick coal seams trend northeastward and occur between Fruitland fluvial sandstone complexes. Fruitland coal seams commonly are extensive, overriding sandstones. Coal beds are fractured reservoirs, and commonly, permeability is greatest in the direction of the dominant fracture set (face cleat). Face cleat strikes in Fruitland coal beds delineate two principal domains. In the southern part of the basin, face cleats strike northward or northeastward, whereas in the northern part of the basin, face cleat strike is predominantly northwestward. Coal seams, major aquifers in the Fruitland Formation, are overpressured in the northern part of the basin due to artesian conditions. These overpressured coal seams commonly are water-productive. In the southern part of the basin, the Fruitland Formation is underpressured, and coalbed methane wells produce little or no water. The composition of Fruitland coalbed gas varies regionally and predictably; both dry and wet Fruitland gases are present, and carbon dioxide content ranges up to 13 percent. On the basis of geologic and hydrologic studies, the San Juan Basin was divided into regions in which Fruitland coal beds have similar reservoir characteristics.
Geologic Characterization and Coalbed Methane Occurrence: Williams Fork Formation, Piceance Basin, Northwest Colorado
(1995) Tyler, Roger; Kaiser, W. R.; McMurry, Ronald G.
The coal-bearing Upper Cretaceous Williams Fork Formation, 1,200 to 2,500 ft thick, is operationally defined on the basis of correlation with the Sand Wash Basin. Net coal thickness is typically 80 to 120 ft and is thickest in a north-south belt west of the Divide Creek Anticline. Depositional setting and thrust faults cause coals along the Grand Hogback and in the subsurface to be in modest to poor hydraulic communication. Thus, meteoric recharge and flow basinward is restricted. Face cleats of Late Cretaceous age strike east-northeast and west-northwest in the southern and northern parts of the basin, respectively, normal to the Hogback thrust front. Parallelism between face-cleat strike and present-day maximum horizontal stress direction may enhance coal permeability in the north. Lineament azimuths lie between 20 to 40° and 280 to 310°; they are not a reliable indicator of subsurface fracture attributes nor of gas production. In the Grand Valley/Rulison and White River/Pinyon Ridge areas, structure and sandstone development control gas production from Cameo coals and/or sandstones. The most productive wells are on structural terraces and anticlines or correspond to Cameo sandstone development, reflecting fracture-enhanced permeability. As predicted, from an evolving coalbed methane producibility model, extraordinary coal-gas production is precluded by the absence of dynamic groundwater flow. The best potential for coal-gas production may lie in conventional traps basinward of where outcrop and subsurface coals are in good hydraulic communication.
Geologic Evaluation of Critical Prodcution Parameters for Coalbed Methane Resources
(1987) Finley, Robert J.
Coalbeds of the United States contain an estimated 200 to 800 Tcf of unconventional gas, much of which is in seams that are unminable or uneconomic (GRID, 1985). Early studies of coalbed methane by the U.S. Bureau of Mines were directed toward degasification in advance of underground coal mining (Rightmire, 1984). The increase in energy prices in the 1970s focused attention on coalbed methane as a potential resource, and subsequently, several hundred wells have been drilled, primarily in the Black Warrior, San Juan, and Piceance Creek Basins. The Gas Research Institute (GRI) has actively supported research aimed at developing the technology for economic production of coalbed methane. At the onset, well completions in coalbed reservoirs were a new and unperfected procedure that required innovative modification of established techniques. Therefore, earlier research efforts were directed toward the engineering problems associated with production, with less emphasis on geologic and hydrologic parameters that control coalbed methane occurrence and producibility. Knowledge of these geologic controls has been found, however, to be important to successful well completions and to the development of regional exploration models.
Geologic Evaluation of Critical Production Parameters for Coalbed Methane Resources
(1988) Ayers, Jr., W. B.; Kaiser, W. R.; Swartz, T. E.; Zellers, Sarah D.
Characterization of coalbed methane occurrence and producibility in the Black Warrior Basin of Alabama indicates that geological factors are the principal controls on the occurrence and producibility of coalbed methane. Results of engineering analysis indicate that application of completion and stimulation techniques may be used to increase recovery once favorable well sites are chosen. Sedimentologic and coal-quality parameters may be used to locate regions for coalbed methane development by characterizing the occurrence, rank, and grade of coal resources. However, high-productivity trends within those regions are localized, and geological data suggest that productivity trends may be predictable based on structural and hydrologic parameters. Several highly productive trends occur along northeast-oriented lineaments. These trends evidently are the surface expression of zones of enhanced permeability which apparently are related to fractures. Productive trends also are associated with areas of low reservoir pressure, and salinity maps indicate that fresh water has migrated toward these areas from the southeast margin of the basin. The available data indicate that structure and hydrology are critical production parameters that may be used to identify favorable well sites within regions containing significant, high-quality coal resources.
Geologic Evaluation of Critical Production Parameters for Coalbed Methane Resources, Black Warrior Basin - Final Report
(1989) Pashin, J. C.; Ward, W. E.; Winston, R. B.; Chandler, R. V.; Bolin, D. E.; Hamilton, R. P.; Mink, R. M.
Characterization of coalbed methane occurrence and producibility in the Black Warrior basin of Alabama indicates that geologic factors are the principal controls on the occurrence and producibility of coalbed methane. Results of engineering analysis indicate that application of completion and stimulation techniques may be used to increase recovery once favorable well sites are chosen. Sedimentologic and coal-quality parameters may be used to locate regions for coalbed methane development by characterizing the occurrence, rank, and grade of coal resources. However, high-productivity trends within those regions are localized, and geologic data suggest that productivity trends may be predictable on the basis of structural and hydrologic parameters. Several highly productive trends occur along northeast-oriented lineaments. These trends evidently are the surface expression of zones of enhanced permeability which apparently are related to fractures. Productive trends also are associated with areas of low reservoir pressure, and salinity maps indicate that fresh water has migrated toward these areas from the southeast margin of the basin. The available data indicate that structure and hydrology are critical production parameters that may be used to identify favorable well sites within regions containing significant, high-quality coal resources.
Geologic Evaluation of Critical Production Parameters for Coalbed Methane Resources, Part II, Black Warrior Basin
(1990) Pashin, J. C.; Ward, W. E.; Winston, R. B.; Chandler, R. V.; Bolin, D. E.; Hamilton, R. P.; Mink, R. M.
Geologic evaluation of critical production parameters for coalbed-methane resources in the Black Warrior basin of Alabama employed an interdisciplinary approach that utilized structural, coal-quality, sedimentologic, hydrologic, and engineering data. Results indicate that geologic factors are a major control on the producibility of coalbed methane and that completion techniques may be used to increase recovery if tailored to specific geologic settings. Sedimentologic and coal-quality parameters may be used to locate regions for coalbed methane development by characterizing the occurrence, rank, and grade of coal resources. However, high-productivity trends within those regions are localized, and geologic data suggest that productivity trends may be predictable. Several highly productive trends occur along northeast-oriented lineaments. These lineaments are the inferred surface expression of zones of enhanced permeability which are related to fractures. Productive trends also are associated with areas of low reservoir pressure, and salinity maps indicate that fresh water has migrated toward areas with low reservoir pressure. The available data indicate that structure and hydrology are critical production parameters that may be used to identify favorable well sites within regions containing significant coalbed-methane resources.
Geologic Evaluation of Critical Production Parameters for Coalbed Methane Resources: Part 1, San Juan Basin
(1990) Ayers, Jr., W. B.; Kaiser, W. R.; Ambrose, William A.; Swartz, T. E.; Laubach, Stephen E. (Stephen Ernest), 1955-
The Fruitland Formation in the San Juan Basin is the major producer of coalbed methane in the Western U.S. Forty-three to forty-nine Tcf of methane occur in 245 billion short tons of Fruitland coal at depths between 400 and 4,200 ft. Thickest Fruitland coal seams trend northwest and occur in the northern part of the basin, northeast of a syndepositional, structural hinge line; they occur in coastal plain facies southwest of Pictured Cliffs barrier/strandplain sandstones. South of the hinge line, northeast-trending coal seams occur in floodplain facies between northeast-trending Fruitland fluvial systems. Face cleat trends in Fruitland coal seams are predominantly northeast in the southern two-thirds of the basin and northwest but variable in the northern third. Suggested targets for enhanced coalbed permeability are tectonic fractures and fractures associated with subtle folds. Fruitland Formation waters are evolved meteoric waters; water composition reflects hydrologic setting. Waters in the north-central San Juan Basin have high alkalinity and low chlorinity; waters in the southern part are Na-Cl type. Distribution of low-chloride ground water in the Fruitland Formation in the north-central basin coincides with the overpressured area and with flow patterns inferred from the head map. The Fruitland Formation acts regionally as a single hydrologic unit or homogeneous aquifer, but large pressure gradients locally indicate that Fruitland strata may be hydraulically disconnected and behave at the field scale as compartmentalized aquifers. Hydrologic studies defined reservoir characteristics and permeability boundaries in the Fruitland Formation. Geologic and hydrologic parameters were used to divide the San Juan Basin into areas in which coal beds have similar reservoir characteristics. Coalbed wells have negative declines early in their production history followed by exponential decline rates at less than 5 percent/year. Sandstone wells that exhibit coal-decline behavior probably are producing coalbed methane indirectly from coal seams.
Structure, Sedimentology, Coal Quality and Hydrology of the Black Warrior Basin in Alabama: Controls on the Occurrence and Produciliblity of Coalbed Methane
(1991) Pashin, J. C.
Geologic evaluation of critical production parameters in the Black Warrior basin employed an interdisciplinary approach that utilized structural, sedimentologic, coal-quality, hydrologic, completion, and production data. Results indicate that geologic structure affected sedimentation, coalification, hydrogeology, and the ultimate occurrence and producibility of coalbed methane. Geologic trend analysis was used to characterize regional coalbed-methane potential, and results indicate that many parts of the basin have untapped resources. Some highly productive trends coincide with northeast-trending structures that apparently are zones of enhanced fracture permeability. Water-production data indicate that many high-permeability trends exist that are not associated with exceptional coalbed-methane production and that the coal beds are structurally compartmentalized reservoirs. Water-level data indicate that all highly productive coalbed-methane wells occur where reservoir pressure has been lowered significantly. Therefore, highly productive areas apparently represent structural compartments where formation pressure has been lowered enough to facilitate desorption of a large quantity of methane. Results of this research suggest that completion technology and field design can be tailored to specific geologic settings to produce from reservoir compartments that are readily depressurized, thereby optimizing reservoir drainage.