This report was prepared as an account of work sponsored by an agency of the _ .
A total of five carbon dioxide (CO2) /sand well stimulations were successfully executed with two Devonian shale operators in Perry and Pike Counties, Kentucky. This new stimulation method offers a minimum formation damage proppant stimulation approach for natural gas producers in the United States. Some operators have been concerned about the frac fluid formation damage associated with the water and chemicals used in conventional foam stimulations, whereas other operators have been concerned about the lack of proppant in straight nitrogen fracs used by service companies today. Two carefully screened geological areas of established Devonian shale production were selected based on active ongoing drilling and completion operations. One selected control area contained an existing set of wells with established production histories. More specifically, one operator furnished three offset wells which were stimulated with the carbon dioxide/sand frac method. The quantity of proppant and fluids pumped during each well stimulation ranged from 23,000 to 43,000 pounds of proppant and from 120 to 160 tons of liquid carbon dioxide. Another operator furnished two offset wells which were each stimulated with approximately 47,000 pounds of proppant and 120 tons of carbon dioxide. The logistics and field layout of a typical carbon dioxide/sand frac treatment has been described and highlighted. The importance and unique aspects of the closed system blender that is required for job execution is discussed. Five stimulation treatments have been reviewed, and stimulation and preliminary production data compared to offset wells stimulated with nitrogen, and explosives. Initial production results indicate more than a 50 percent increase in production rate compared to nitrogen fraced wells in the Pike County area. In addition, production is also 4.8 times better than conventional shot wells in the same area. These results are encouraging enough to formally combine existing pumping equipment, a closed system blender, and liquid carbon dioxide supplies to develop a new fracturing service in the eastern U.S. A total of 22 additional jobs are planned in the eastern U.S. in low permeability gas formations over the next year.
Summary A CO2 minitest was conducted in a high-oil-saturation, low-permeability, carbonate reservoir. Incremental oil production exceeded 4,100 bbl (652 m ) as a result of the injection of 1,500 tons (1360 M ) of CO2. Few problems were encountered in planning and conducting, this field test. Introduction The U.S. DOE Morgantown Energy Technology Center has studied eastern U.S. oil reservoirs for many years. The goal of these studies has been the more complete recovery of oil through the application of secondary and enhanced oil recovery (EOR) methods. This test was one of a series of CO2 injection projects conducted by or in cooperation with the U.S. DOE (formerly U.S. ERDA) in West Virginia. The Hilly Upland oil field in north-central West Virginia was selected for this study because it presented a unique opportunity to investigate the effects of CO2 injection in a primary recovery reservoir with naturally flowing wells. The objectives of the project wereto determine the feasibility of injecting CO2 into a low-permeability reservoir,to increase oil recovery, andto obtain first-hand field experience with the CO2 displacement process, problems, etc. The information and experience trained should be of value in the design of future EOR projects using CO2 as the displacing medium. This work was conducted in cooperation with the Allegheny Land and Mineral Co. (AL and M) in Clarksburg, WV, which owns and operates the leases and which, as prime contractor, performed most of the field work. History Although one very old, depleted oil well was located at the extreme western edge of the productive area, the field actually was discovered in 1963 when Rhodes No. 1. Permit No. LEW-1103D, was drilled on an adjacent property east of the project area. The first Hilly Upland well was drilled on AL and M leases in 1968. The project area, approximately 10 acres (40 500 m), is defined as that part of the field including Wells A-359, A-361, A-390, and the injection well, Al- 1 (Fig. 1). The old well (unnumbered) and Wells A-527 and A-389 also were monitored, but no evidence of the effects of CO2 injection was found in them. Among the wells in the project area, initial flowing production of individual wells after stimulation ranged from 5 to 22 STB/D (0.8 to 3.5 stock-tank m /d). Peak field production of 6,100 STB (970 stock-tank m ) was reached in 1970. The field production rate had declined to 3 STB/D (0.5 stock-tank m /d) per well when CO2 injection was started in Sept. 1976. Cumulative production from the project area at that time was 28,500 STB (4530 stock-tank M ). No form of artificial lift had been used in the field up to that time. One additional well (A-527) was drilled and cored in Feb. 1975 north of the project area into the gas cap and was completed as a gas well. This well's cumulative oil production was less than 10 bbl (1.6 m). The test area had the advantages of relatively new wells, and the reservoir had high oil saturations. A permeability pinchout adjacent to the test area helped contain the injected fluids. The reservoir is less than 2,000 ft (610 m) deep, so well drilling and operations were relatively inexpensive. The reservoir was, however, relatively complex. There were fractures present, and these were characterized through extensive studies. Geology The Hilly Upland oil reservoir occurs in the Greenbrier limestone formation of middle Mississippian age. JPT P. 1781^
Introduction The basic success of an Appalachian independent oil and gas operator is dependent upon the availability of good leases and drill sites which lead to productive reservoirs. Prospects are available through utility companies, lease brokers, and other independents. The results of drilling must live up to the expectations of the investor. Investment capital may be raised through broker-type groups, individual sales or more typically through direct offerings by the operator. Recently the offerings are commonly structured as limited partnerships with the operator as General Partner. The prospectus is prepared to meet SEC registration requirements; however, are not usually registered. There are many areas in the Appalachian Basin which have great potential for exploration and development drilling. With reasonable incentives to increase drilling, the independent will find and develop significant volumes of much needed oil and natural gas. PRODUCT PRODUCT The "product" which is the basis of the Appalachian independent oil and gas operator opportunity, is the lease or well location. These leases can be categorized as exploration or development prospects and are available through several different options:(1) Farmouts from utilities or major companies are generally available. Since these larger companies control an estimated 85 percent of the leased acreage in the Appalachian Basin, it is probably most feasible to approach one of these majors to arrange for an assignment of drill sites. The utility/pipeline companies regularly require that they have a call on the natural gas produced and a time limit as to completion of the drilling of these locations. The major oil and gas companies often will require up to a 1/16th overriding royalty.(2) Leases through brokers who usually accumulate acreage in blocks, charge in the range of $5 to $10 per acre and may add an override of possibly 1/32nd.(3) The independent operator may do his own leasing to accumulate the prospects for a drilling program. This is a must to protect him in years to come for continued operations. In every case the leases are assigned or sold without warranty of title. The operator must have an attorney run a title check on each lease to verify that the lessee docks in fact have the oil and gas rights. This is commonly called "clearing title."The acquisition of good prospects for a drilling program is extremely important for success in this business. It is the basic commodity that can make or break the operator. TYPE OF PRODUCT Development wells are the most common type drilling program presented by the typical independent operator. A development presented by the typical independent operator. A development well is a well directly offsetting actual proven production. Occasionally in a development well program an operator may include several "stepout" wells. The definition of stepout, that is generally accepted, is a location within one mile of existing production. Exploration programs are not as prevalent as development well programs. It is a necessary incentive to control larger blocks of acreage surrounding an exploration prospect. Due to the strategraphic reservoir development in the Appalachian Area, the shallow exploration prospects are mainly extensions of trends and also deepening of old shallow oil and gas fields.
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