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This paper summarizes MetFuel Inc.'s experiences in conducting a pilot test of the coalbed methane potential of an undeveloped area in the southern Black Warrior Basin. The pilot project was designed to gather baseline reservoir data, determine the project was designed to gather baseline reservoir data, determine the viability of further development by field experience, and learn how to complete and stimulate coal seams in this area. The pilot project provided valuable insights in terms of drilling practices, defining provided valuable insights in terms of drilling practices, defining target intervals, hydraulic fracture geometry and height growth, perforation placement, canister test procedures, and reservoir perforation placement, canister test procedures, and reservoir permeability versus stress. A wealth of baseline reservoir data was permeability versus stress. A wealth of baseline reservoir data was also collected. Continued production from the pilot project wells is required to determine the economic viability of large-scale development in this area.
MetFuel, Inc. is developing a coalbed methane prospect in the relatively undeveloped southern portion of the Black WarriorBasin. Before developing a coal seam in a new area, a pilot program should be implemented to gather data so the feasibility of full scale development can be evaluated. Key factors to be determined to optimally design the large scale development project are gas content and formation permeability. This pilot project has been designed to (1) gather baseline reservoir data, (2) determine the viability of further development by field experience, (3) provide insights into potential operational problems involved with drilling and potential operational problems involved with drilling and completing wells in this area, and (4) learn how to complete and stimulate the coal seams in this area.
A five-spot pilot has been drilled in the Big Bend area of Black Warrior Basin to accomplish the goals set forth. The location of the five-spot pilot project in relation to other coalbed methane activity in the basin is shown in Fig. 1. This paper presents a status report on the pilot project.
At the time of this writing, we do not have any long term production data because no water disposal facilities have been production data because no water disposal facilities have been installed in the area of the five-spot pattern. As such, we have only included information concerning the various completion and stimulation methods chosen for the pilot wells. Only time and long term production data will allow us to properly evaluate the completion methods tested in the pilot project.
PILOT PROJECT DESIGN PILOT PROJECT DESIGN Because coalbed methane well production depends on the interference from adjacent producing wells to reduce reservoir pressure over a large scale area in order to initiate gas desorption, pressure over a large scale area in order to initiate gas desorption, a five-spot pilot project was designed to test the potential productivity of the coals found in the Big Bend area of the Black Warrior productivity of the coals found in the Big Bend area of the Black Warrior Basin. Six possible target coal seams are available for completion as shown in the generalized stratigraphic column in Fig. 2. The locations of the pilot project wells are shown in Fig. 3.
A goal of the pilot project was to define the zones of highest potential for completing in a large scale development project. potential for completing in a large scale development project. Therefore, the pilot wells were drilled through all of the six potenial target seams. The average total depth (TD) for the pilot wells was potenial target seams. The average total depth (TD) for the pilot wells was approximately 5300 feet. Because we wanted to determine the permeability and productivity of individual target coal seams, each permeability and productivity of individual target coal seams, each of the pilot wells was cased and cemented to TD as shown in Fig. 4. The original pilot project design called for isolated well testing and production testing of each of the six target coal groups in each of the five pilot wells. It was quickly discovered that this idealized approach was impractical because injection/fall off testing of individual seams requires one to two weeks and production testing of individual target seams can take as much as three months of uninterrupted production.
Because the J coal seams require, significant additional drilling (and costs) to complete, the testing of the potential of the J-seam was given a high priority. The reasoning for this being that if we could determine that the J-seams are not potentially productive, tremendous savings could be achieved in drilling costs of additional development wells. Therefore, the J-seams were tested using injection/falloff tests and completed and produced for one to two months in an isolated fashion in the first two wells drilled in the pilot program. pilot program. P. 487
Abstract Coalbed methane production is viewed as an attractive source for the growing US natural gas demand. Undeveloped resources of coalbed methane in the United States have been estimated at 60 Tcf. A majority of the coal in the USA is accessible at shallow depths, making well drilling and completion inexpensive. Finding costs are also low since methane occurs in coal deposits, and the location of the nation's coal resources are well known. Millions of acres of potential coalbed methane gas production identified in the Illinois and Western Interior Basins are currently being evaluated with multi-well pilot projects. The coals of interest vary from 300 to 2,300 feet in depth, have moderate to high ash content, low moisture content, and are High Volatile C to Medium Volatile in rank. The coal seams range in thickness from one to five feet and have gas contents of 1 to 325 scf/ton, with measured permeabilities on the order of .1 to 100 mD. The primary purpose of a pilot test program is to determine gas deliverability potential and initial water production. Well spacing, time to dewater, and ultimately time to reach maximum gas production are crucial to overall project development economics. Secondarily, the pilot programs are designed to confirm gas contents and permeability estimates obtained from initial data wells. The pilot wells are placed in such a way to maximize well-to-well interference during a reasonably short production test period (4 to 6 months). This paper presents the initial results of several ongoing pilot projects in both basins. Parameters such as full-field well spacing, water disposal requirements and facilities, artificial lift criteria, gas deliverability, and ultimate recoveries can be estimated and asset development economics determined. Introduction The Western Interior Basin (Figure 1a) is an intercratonic depression located in Southwestern Iowa, western Missouri, Southeastern Kansas, Eastern Kansas, and Northeast Oklahoma. The basin is bounded on the west by the Nemaha Ridge, the Precambrian craton to the north, the Mississippi River Arch and Ozark Uplift to the east, and the Marathon Overthrust Belt to the south. The Nemaha Ridge is part of a failed mid-continent rift system and remains tectonically active today. The Nemaha Ridge formed an escarpment during Pennsylvanian time that terminated the westward expansion of swamp development. Deposition during Paleozoic time in the basin was noted for limited deposition of all geologic units accented by long periods of erosion and uplift. The basin has been the subject of on-going thermal activity, migration of low temperature hydrothermal fluids from south to north and heating along the Nemaha Ridge. Numerous intrusions have been documented in the basin especially in Woodson County, Kansas and along the western flanks of the basin. Many of the coals in the basin contain sphalerite in the cleat systems as far north as northwestern Missouri and in association with certain fault systems and low temperature hydrothermal dolomite. Bottom hole temperatures in coals in Osage County, Kansas are approximately 92° Fahrenheit at 1,500 feet. Coals at a similar depth in the Illinois Basin are 65° Fahrenheit. The Cherokee and Marmaton Group increase in thermal maturity, from immature to marginally mature, from north to south and east to west towards the Nemaha Ridge. The oil migration path and the API gravity of the oil throughout the basin are associated with changes in coal rank.
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 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.
Coal mines in the Appalachian Basin emit approximately 180 million cubic feet (MMcf) of high-quality methane into the atmosphere daily. The existence of mines in West Virginia, southwest Virginia, eastern Kentucky, Ohio, Pennsylvania, Tennessee, and Alabama with high gas emissions of over 100 thousand cubic feet per day (Mcf/d) suggests that further investigation into the economic development of this unconventional energy source is warranted. Appalachian coals occur as multiple beds, individually up to 14 feet thick (Pittsburgh coalbed in Pennsylvania and West Virginia). The gas content of these bituminous coal seams has been measured at 93 cubic feet per ton (cu ft/t) from a depth of 149 feet (Waynesburg coalbed, Pennsylvania) to over 560 cu ft/t at 1,764 feet (Pocahontas Pennsylvania) to over 560 cu ft/t at 1,764 feet (Pocahontas No. 3 coalbed in West Virginia); in the anthracite region, 690 cu ft/t have been measured where the overburden is 685 feet thick (Peach Mountain coalbed).
Detailed studies in the southern Warrior Basin indicate the presence of up to 20 trillion cubic feet (Tcf) of gas, and preliminary work in the Central and Northern Appalachian Basins suggests a resource of 50 and 80 Tcf, respectively. Many coal operators are realizing the production potential of coalbed methane. In Buchanan County, Virginia, the Island Creek Coal Company produced up to 434 Mcf/d from 12 horizontal boreholes drilled into the mine face. Waynesburg College in Pennsylvania will realize a savings of $25,000 toward their annual energy bill from a 1,450-foot vertical well drilled on campus. In Alabama, U.S. Steel's mines just began commercial production, and sold 25 Mmcf to a gas pipeline company in December 1981; and Jim Walters Resources has begun an ambitious program to drill up to 700 wells with a predicted total production of 60 billion cubic feet (Bcf). production of 60 billion cubic feet (Bcf). These examples of the successful exploitation of a resource formerly considered only a hazard to coal mining indicate a promising future for coalbed methane.
Since the mid-1800s, coal mines in the Appalachians have had a history of mine disasters related to the gassy coalbeds throughout the area. These problems continue despite modern safety methods because active mines are pushing deeper into virgin seams with higher relative gas contents. For Appalachian mines in 1975, the methane emission rates totaled over 180 MMcf/d; and for individual mines, rates can be as high as 11.6 MMcf in the Loveridge Mine in Marion County, West Virginia. Conversely, this potential hazard can be an energy resource to be developed either in conjunction with mining or independently.
To further investigate the potential of this resource, in 1977 the U.S. Department of Energy (DOE) began the Methane Recovery from Coalbeds Project (MRCP) to characterize and help to develop Project (MRCP) to characterize and help to develop its utilization. In addition to government-sponsored research and development, numerous commercial firms--many located in the Warrior Basin-- have become involved with coalbed methane's characterization and exploitation.
TRW has been involved since the inception of MRCP in the collection and analysis of data, and we are now attempting to collate the findings to form a coherent picture of the coalbed methane resource potential for the entire Appalachian region. The potential for the entire Appalachian region. The object of this paper is to explore the magnitude and potential of this resource throughout the Appalachian Basin.
PHYSIOGRAPHY/GEOLOGY PHYSIOGRAPHY/GEOLOGY The coal-bearing Appalachian Basin extends over parts of nine states (Figure 1), and includes the following subdivisions: the Northern Appalachian, Central Appalachian, and Southern or Black Warrior Basins.
PERSPECTIVES OF METHANE RECOVERY FROM COAL BEDS IN POLAND J. Siemek, S. Rychlicki and C. Rybicki, University of Mining and Metallurgy, Department of Petroleum Engineering, Cracow, Poland. Abstract. Coal beds and methane-both free and adsorbed in coal, appear in the south of Poland in the Upper Carboniferous in two basins: Upper Silesian Coal Basin (USCB) and Lower Silesian Coal Basin (LSCB). At the depth of 3o(r1600 m the methane reserves are estimated at 350 to 1300 rnld m3 for USCB and ca. 20 mld m3 for LSCB. Methane content in coal varies between O and 22 m3/tpc, to significantly increase from the depth of 600 m, reaching average values of 4.7-7.0 m3/tpc. Discrepancies in estimation are due to different calculation methods; the full geostatistical analysis method- structural analysis-was not applied, however. Prognoses, apparently optimistic, determine the final recovery of methane from coal beds for ca. 5 mld m3/year for USCB, and ca. 300 min m3 for LSCB, which together with the production from the Polish gas reservoirs would give ca. 12 mld m3/year in the year 2010. For the comparison's sake, the Polish consumption of gas is now ca. 11.8 rnld m3, being about 9% of total primary fuel consumption in Poland. Methane from coal beds was recovered earlier but used in less quantities (ca. 190 mln m3/year). It came from 18 USCB mines. Utilization of methane from coal basins aims at the reorientation of the Polish energy industry to the increased use of hydrocarbon fuels. Besides, the use of methane, especially in the Upper Silesia region, will significantly improve the ecological situation, limiting the emissions of SO,, CO,, NO, and dusts. The priorities of methane utilization are as follow: delivery to local receivers, for households, near big agglomerations Katowice, Opole, Bielsko; heating, housing estates, country, balance top needs ; for local industrial works, metallurgical, ceramic, chemical plants, glass works; electric gener- ation. Now a few foreign companies are interested in methane exploitation in Poland, e.g. McCormick Energy Inc., USA, Amoco, Conoco, Electrogaz Ventures (Poland-USA), Metanel (Poland). There has been an auction of the licence for methane exploitation. The fact that methane appears in coal beds has been known since the beginning of the mining industry. The gas was generally treated as a consider- able hindrance in the exploitation of coal as a fuel. It has created a great hazard'for the miners in the form of explosions and outbursts of rock and coal. For more than ten years the matter of methane enclosed in coal, treated as a fuel, has raised interest in many countries, e.g. U.S.A., Australia, China. Research has been carried out on the content in coal, ways of deposition as well as methods of exploitation and leakproof transport to the surface. Poland has also taken an interest in methane, coming from coal, as a fossil fuel. There are three coal basins in Poland (Fig. 1): - Upper Silesian Coa
Abstract Since the late 1990's, operators have drilled a number of coalbed methane (CBM) core and exploration wells to define the gas resource potential of the vast and relatively unexplored Jurassic Walloon Subgroup (SG) in the Surat Basin. Unfortunately, early pilots used completion techniques that failed to fully assess the true potential of this reservoir. Firstly, openhole completions were trialed but had limited success because of fines influx and well collapse. Next, cased and cemented wellbores incorporating hydraulic fracturing stimulation treatments were attempted to improve wellbore stability, reduce fines influx and increase gas production; these wells were ineffective and many experienced problematic casing failures. Finally, an isolated, openhole, under-reamed completion technique was trialed and achieved commercial flow rates representative of the drill-stem testing data indicated from earlier exploratory drilling. This paper describes the process, experiences and results leading to the present completion strategy. We note production, permeability and skin factors associated with early completions, as well as results obtained from large-scale implementation of this more effective completion method. As a result of this change, the resource potential of the Walloon SG has grown significantly and the operator has proven 3,712 Bcf of reserves from a previously undeveloped resource area. Introduction It has been 10 years since the first well was drilled to investigate the CBM potential of the Middle Jurassic Walloon SG in the Surat Basin, with Queensland Gas Company (QGC), the operator, beginning exploration in 2000 (Fig. 1). Today, the Walloon SG comprises nearly 697 PJ or 16.3% of the 2P CBM reserves and 73,300 PJ or 54.0% of the CBM resources attributed to the eastern basins of Queensland. Whilst impressive, these results were not generally believed to be the most likely outcome to even the most optimistic observers only three years ago. Whilst the CBM characteristics of the Walloon SG are very favorable for producing gas, the speed in the recent development of the Walloon SG has predominantly hinged on the successful definition of a completion strategy capable of delivering commercial gas rates. However, at this point two years ago, pilot testing by all operators in the Basin had been problematic and no pilot projects had effectively demonstrated commerciality. In this case, the operator has been painfully reminded that whilst successful exploration planning and execution can put you on the road to success, the potholes in pilot planning and testing can produce seemingly insurmountable hurdles to a successful outcome. As a result of changes in engineering and management personnel within the company, past results were reviewed and critical errors were identified; then an alternative and more effective completion strategy was formulated and implemented. In this paper, we will describe some of the unique features enhancing production on the Undulla Nose, recount the chain-of-events that eventually led to a successful completion outcome, and provide results data realizing the full potential of a good exploration start. Background Prior to the operator commencing CBM exploration in the eastern Surat Basin only one CBM well had been drilled specifically targeting the Walloon SG- Anulka NL's Southeast Teatree #1. Because of this dearth of Walloon SG data, a new strategy was adopted. The operator commenced a review of all petroleum, stratigraphic, coal exploration and water wells drilled in the eastern Surat Basin. A large percentage of these conventionally targeted, exploration wells (>95%) did not have natural density logs, which would have enable coal thickness to be accurately determined. Because of this, sonic logs were used to estimate coal thickness, but these logs could not be used with any veracity to correlate seams.