In the fall of 1972, the Bureau of Mines began an experiment to investigate the technologic, economic, and environmental considerations of underground gasification of a western subbituminous coal. The gasification site is near the town of Hanna, Wyoming, approximately 70 miles northwest of Laramie. The test results indicate that gas volumes and gas heating values have fluctuated over a wide range depending on operating conditions. The ranges have been from 50,000 to over three million standard cubic feet per day of produced gas with a composite heating value from 30 to 465 Btu per standard cubic foot. Even though these fluctuations have occurred, a semi-steady state condition existed for a six-month period. From September 1973 through February 1974 a low Btu gas averaging about 130 Btu per standard cubic foot was produced at an average rate of 1.6 million standard cubic feet per day. A material balance made during this period indicated:There was little or no underground gas leakage from the site;About 80 barrels of formation water were consumed each day;Between 13 and 46 tons of dry coal were affected each day depending on the assumptions made; andFrom 23 to 65 percent of the energy of the coal being subjected to carbonization and/or gasification is being recovered. If the gas can be sustained at this relatively steady Btu content and production rate, it could be used directly to fire a boiler or to fuel a combined gas turbine-steam turbine cycle in electric power stations. The average amount of energy power stations. The average amount of energy produced from this small field test would have produced from this small field test would have been adequate to supply fuel for about a one megawatt power station. Introduction Interest in underground coal gasification has been stimulated recently by the Nation's growing energy demand. Its potential for generating plentiful supplies of fuel gas without the environmental disturbance of surface mining and without exposing workers to the hazards of underground coal mining is especially promising. While not expected to replace coal mining, it offers an alternative method of bringing the energy value of the coal to the surface. If feasible, this clean energy form could supplement the gas supply used to produce electricity, particularly in the industrial sector. It may also be possible to upgrade the gas to pipeline quality or to produce methanol as a possible substitute fuel for gasoline. The role of oil and natural gas as sources of energy is almost as well known as the shortage of these vital fuels. More than three-fourths of the energy used in the United States in 1972 was derived from these sources. Coal, the most abundant fossil fuel, supplied only 17 percent of the Nation's energy needs in that year.
The economic exploitation of the East Canton Oil Field truly began with the technology advancement of hydraulic stimulation in the early to mid 1940's. This field which encompasses approximately 175,000 acres in Stark, Carroll and Tuscarawas Counties of northeastern Ohio, realizes the vast majority of its production from the Clinton Sandstone reservoir which is located at a depth of 4000-6000 feet. Primary development of this field on 40 acre spacing, has resulted in the drilling and completion of in excess of 3100 wells, a recovery to date of approximately 86 million barrels of oil and an expected Ultimate Recovery of 140 million barrels of oil or 9% of the 1.5 billion barrels of oil believed to be in place. Due to the low recovery factors which are typical of low permeability, solution gas drive reservoirs, efforts have been underway to identity techniques capable of improving the ultimate recoveries from the field. Two (2) methods which Belden & Blake has been examining, target the improvement of recoveries from the existing drainage patterns as well as the infield reserve growth from development of undrained areas within the tight (<0.1 md), stratigraphically compartmentalized reservoir. The "Marlboro Field", located in the extreme north of the much larger East Canton Field was selected as a pilot area for an initial study. Figure 1 Phase I of this study was to identity the impact that injecting natural gas into existing wells, repressuring the near wellbore/hydraulic fracture system, allowing for a "soak" period then returning the well to production would have on ultimate recovery. Computer simulations conducted by International Gas Consultants Inc. (IGC) indicated that the average drainage areas of this field were approximately 1/2 of the development spacing and that by injecting gas in a Huff-n-Puff fashion could result in incremental recoveries in the order of 1 new barrel of oil per 30 Mcf of injected gas. This study also indicated that in combination with infill drilling, overall oil recoveries within the field could increase by an estimated 100% over that achieved from primary recovery alone. Based on this study, two (2) Huff-n-Puff cycles were undertaken in a pilot area within the Marlboro Field resulting in incremental recoveries of 500 barrels of oil per well or 1 new barrel of oil per 40 Mcf of injected gas. To address the infield reserve growth potential of this field from infill drilling, Belden & Blake drilled two (2) infill wells in late 1996 and identified commercial reserves in an area where some level of pressure depletion had occurred. In an effort to better identity high quality infill sites, S.A. Holditch and Associates was contracted to conduct a "Moving Domain Analysis" utilizing the reservoir and production data from the field. Based on this study, between 10 and 30 potentially economic infill sites have been identified within the Marlboro Field. Efforts are currently underway to validate that study. The study and its field validation will not be addressed in this paper but will be the topic of a future publication. The basis for the Moving Domain process has been well documented in previous studies. Introduction The geologic environment of the Clinton Sandstone has resulted in a stratigraphically complex reservoir. The Clinton sand unit is Lower Silurian in age and lies between the Dayton Limestone (Drillers Packer Shell) and the upper Ordovician Queenston formation (Drillers' Red Medina) at depths of 4,600 to 5,300 ft. Within the East Canton Field, which encompasses approximately 175,000 acres, the productive interval consists of interbedded shale, siltstones and sandstones ranging in thickness from 50 to 250 feet in thickness. These sandstone and siltstone lenses possess significant lateral and vertical discontinuity typical of a stratified reservoir. It is due to the interbedded sandstone and siltstone lenses, together with the inherently lower recoveries of this tight, solution gas drive reservoir that have resulted in low recovery efficiencies in the order of 8-10 % of the OOIP. Based on projected ultimate recoveries of 140 million barrels, the remaining hydrocarbons in place are expected to exceed 1.3 billion barrels. The magnitude of this remaining hydrocarbon resource has been the impetus for past and current IOR/EOR efforts. P. 23^
In this reservoir study of the Clinton sand, East Canton oil field, Ohio, results indicate that a properly engineered waterflood may be feasible for secondary oil recovery. Waterflood forecasts that account for a wide range of reservoir conditions are included and can be used for preliminary waterflood performance estimates. Introduction The Morgantown Energy Research Center of the U.S. Bureau of Mines has, for several years, engaged in studies of eastern U.S. oil reservoirs. The goal has been more efficient recovery and more nearly complete recovery of oil through the application of the various secondary-recovery mechanisms. The East Canton oil field in northeastern Ohio was selected for this study because of the impact of its potentially large reserves on the supply of Pennsylvania potentially large reserves on the supply of Pennsylvania Grade crude oil. Because of the unusual reservoir characteristics, secondary-recovery operations in the Clinton sand will be especially challenging for operators and engineers. Previously published reports dealt with reservoir geology and primary recovery in the East Canton field. It was recently reported that waterflooding might be feasible under certain conditions. Here we shall describe, in more detail, the reservoir factors that pertain to waterflooding, and provide the operators with a method for estimating possible oil production by waterflooding from their properties in production by waterflooding from their properties in the East Canton field. Location, History, and Development The East Canton oil field is composed of an or parts of 11 townships in Stark, Carroll, and Tuscarawas Counties in northeastern Ohio (Fig. 1). Active drilling started in 1965 in western Rose Township, Carroll County. Rapid development of the East Canton oil field, however, did not start until Oct., 1966, when the discovery well of the East Canton pool was completed. To date, the western and northern limits of the field have been defined, but the eastern and southern edges of be extended by future drilling. At present, the proved to semiproved productive area is approximately 22 miles long and 5 to 7 miles wide. By July, 1970, over 1,000 wells had been drilled, and several operators were drilling additional wells. Although ultimate primary recovery will vary depending on reservoir characteristics, volumetric calculations indicate recoveries between 28,000 and 63,000 bbl/well, based on 40-acre spacing. More recent decline curve analysis for a 15-well study area shows an approximate primary recovery of 43,000 bbl/well, using an economic limit of 90 bbl/well/ month. Initial production rates of individual wells in the field, as reported by completion records, ranged from a few barrels to over 300 BOPD after fracturing. Most wells produce from a few thousand cubic feet to several hundred thousand cubic feet of gas per day. Initial bottom-hole pressures of approximately 1,500 psi have been observed. Very few wells were plugged psi have been observed. Very few wells were plugged as dry. Peak production of the fieldapproximately 13,000 B/D was reached in Aug., 1968. Cumulative production passed the 10-million-bbl mark by July, production passed the 10-million-bbl mark by July, 1970. JPT P. 1371
The U.S. DOE's gas resource program aims at resolving existing technological barriers to effective recovery of natural gas from Devonian shale and methane from coalbeds. Upon completion of these projects, DOE expects the technology developed jointly with industry to result in wide-scale recovery and use of these new sources of natural gas. Introduction Natural gas continues to be one of the major sources of energy produced and used in the U.S. Declining gas reserves and curtailment of supplies have reemphasized the major influence this energy source has on the U.S. economy. The U.S. DOE is investigating several options for increasing the supply, including a program for unconventional gas recovery (UGR). Four UGR projects currently are being assessed: western tight gas sands, geopressured reservoirs, Devonian shales, and methane from coalbeds. Both the Devonian shale and methane from-coalbeds projects are paramount in this assessment, since they underlie a large section of the U.S. The eastern (Devonian) shales contain a vast, essentially unexplored volume of natural gas. This area could represent new gas recovery from approximately 250,000 sq miles throughout the U.S. Studies by the government and industry have been focused on shale characterization to determine the magnitude of potential gas reserves and technology development needed to improve current state-of the-art stimulation techniques. The initial R and D results have shown promise and point out the technology needed for successful development. The goal of the methane-from-coalbeds project is to provide natural gas from coal seams. While coal itself is recognized as a major energy source, it also contains vast quantities of methane gas. This methane source is not new, since coal mine operators have been aware of its presence and release into the atmosphere during mining operations. Technology studies are being conducted to learn the production potential of this methane and to show how this gas potential of this methane and to show how this gas may be put to widespread use. Devonian Shales The Devonian shales of the Appalachian, Michigan, and Illinois basins have produced natural gas since the 1800's. These shales in the eastern U.S. (Fig. 1) contain a high volume of gas. Independent estimates of the recoverable gas range from 3 Tcf to several hundred times that amount. To date, the gas produced from these shales has been limited to an produced from these shales has been limited to an estimated 2.5 Tcf because of the unpredictable behavior and economics shown by existing Devonian shale wells. Similarly, these uncertainties have restricted private-sector R and D funding and development of technology needed for Devonian shale gas production. JPT P. 703
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