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 No. 8829 
 
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J£J 8829 
 
 Bureau of Mines Information Circular/1980 
 
 Review of Horizontal Drilling 
 Technology for Methane Drainage 
 From U. S. Coalbeds 
 
 By Gerald L. Finfinger and Joseph Cervik 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 

 Information Circular 8829 
 
 Review of Horizontal Drilling 
 Technology for Methane Drainage 
 From U. S. Coalbeds 
 
 By Gerald L. Finfinger and Joseph Cervik 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 Cecil D. Andrus, Secretary 
 
 BUREAU OF MINES 
 
 Lindsay D. Norman, Acting Director 
 

 This publication has been cataloged as follows: 
 
 Finfinger, Gerald L 
 
 Review of horizontal drilling technology for methane 
 drainage from U.S. coalbeds. 
 
 (Information circular - Bureau of Mines ; 8829) 
 Bibliography: p. 18-19. 
 
 L Coal mines and mining — United States— Safety measures, 2. 
 Mine gases. 3. Methane. 4. Boring. I. Cervik, Joseph, joint author. 
 II. Title. III. Series: United States. Bureau of Mines. Information 
 circular ; 8829. 
 
 TN295.U4 622s [622'. 8] 
 
 80-13976 
 

 ^ 
 
 
 CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 1 
 
 Underground drill equipment 2 
 
 Drainage and control technologies 11 
 
 Experience with horizontal drilling 14 
 
 <^2 Pittsburgh coalbed, Pa. and W. Va 14 
 
 Sunnyside coalbed, Utah 15 
 
 Beckley coalbed, W. Va 15 
 
 Mary Lee and "Blue Creek" coalbeds , Ala 15 
 
 Pocahontas No. 3 coalbed, Va 16 
 
 Hartshorne coalbed , Okla 16 
 
 "B" seam, Colo 16 
 
 Summary 16 
 
 References 18 
 
 Appendix. --Drill units 20 
 
 ILLUSTRATIONS 
 
 1. Handheld air drill 2 
 
 2. Post-mounted electrohydraulic drill 3 
 
 3. Longyear horizontal drill 3 
 
 4. Longyear power unit 4 
 
 5. Lambert drill 4 
 
 6. Acker Drill Co. drill 5 
 
 7. J. H. Fletcher and Co. drill 6 
 
 8. Longyear Drill Co. drill 7 
 
 9. Victor drill 8 
 
 10. Dresser drill 9 
 
 11. Atlas Copco drill 10 
 
 12. Spring-loaded ball valve that closes automatically to prevent the 
 
 flow of methane under unsafe conditions 12 
 
 13. Steel pipeline, 3/4-inch PVC pipe, sensor head 13 
 
REVIEW OF HORIZONTAL DRILLING TECHNOLOGY 
 FOR METHANE DRAINAGE FROM U.S. COALBEDS 
 
 by 
 
 Gerald L. Finfinger 1 and Joseph Cervik 
 
 ABSTRACT 
 
 This Bureau of Mines publication reviews underground methane drainage pro- 
 grams being conducted in various coalbeds. Equipment used in drainage programs 
 such as drills, underground pipelines, and methane monitoring systems is described. 
 
 INTRODUCTION 
 
 The Bureau of Mines has been conducting research in mine safety since its 
 inception in 1910. Because uncontrolled release of methane from a coalbed is 
 a serious safety hazard in underground coal mining, the Bureau has conducted an 
 extensive program to study methods of controlling methane emissions. An impor- 
 tant part of this program is the work done to determine the feasibility and 
 effect of methane drainage from coalbeds before mining. Previous work includes 
 studies aimed at understanding the formation and migration of methane in coal- 
 beds (2, 8) 3 and field test methods to remove methane ahead of mining (5-6, 9). 
 One of the most effective methods of degasif ication has been the drilling of 
 small-diameter (3- to 3-1/2-inch) drainage holes horizontally into the coal- 
 bed. Horizontal holes have recently been drilled to lengths more than 
 2,000 feet by Bureau personnel and others (4, 10, 13). A large part of the 
 Bureau's research effort has been directed toward developing safe and effi- 
 cient techniques for drilling boreholes and conveying the flow of methane to 
 the surface. 
 
 Experience has shown that underground horizontal boreholes have a great 
 potential for producing large-volume flows of methane. Every foot drilled in 
 the coalbed from underground locations is productive and gas flows increase as 
 hole length increases. In using horizontal boreholes, dewatering pumps are 
 not necessary because gas pressure forces water out of the hole so that 
 methane can be recovered through the use of simple and inexpensive gas-water 
 separators. 
 
 Geologist. 
 
 Supervisory Geophysicist. 
 
 All authors are with the Pittsburgh Research Center, Bureau of Mines, 
 
 Pittsburgh, Pa. 
 Underlined numbers in parentheses refer to items in the list of references 
 
 preceding the appendix. 
 
UNDERGROUND DRILL EQUIPMENT 4 
 
 When the Bureau began its 
 horizontal drilling program, 
 very little information on 
 drilling techniques was avail- 
 able. Early field studies 
 were conducted to determine 
 the proper procedures for 
 drilling short horizontal 
 boreholes (_7) . The first 
 drills used were handheld 
 (fig. 1) or post -mounted and 
 electrohydraulic (fig. 2). 
 These drills are easily 
 transported but are not capa- 
 ble of easily drilling holes 
 to lengths of up to 1,000 
 feet. Recognizing the poten- 
 tial of long horizontal 
 drainage holes for degasifi- 
 cation of coalbeds, the 
 Bureau studied factors that 
 influenced bit trajectory, 
 developed methods and equip- 
 ment for controlling bit 
 trajectory, and designed, 
 built, and tested a longhole 
 drill unit for drilling 
 horizontal boreholes to at 
 least 1,000 feet. 
 
 E. J. Longyear Co. 5 designed the Bureau's first electrohydraulic longhole 
 drill equipment (figs. 3-4). The drill unit is equipped with gages to monitor 
 bit rotational speed, torque, and thrust. The thrust potential of the drill 
 unit is 13,000 pounds at 2,000 psi hydraulic pressure. Feed length is about 
 11 feet and the overall length of the drill unit is about 18 feet. The power 
 unit (fig. 4) consists of a 30-hp, 440 vac motor that drives hydraulic pumps 
 to operate the thrust and spindle rotation motors on the drill unit. Using 
 the Longyear drill, horizontal boreholes have been drilled to lengths of 
 2,110 feet without reaching the capacity of the drill unit (4). 
 
 One disadvantage of the Longyear drill (fig. 3) is its 18-foot length, 
 which makes it difficult to maneuver in underground locations. The drill 
 could be shortened to facilitate underground handling, but then the 11-foot 
 feed would be sacrificed. An electrohydraulic longhole drill that is much 
 
 ^This report includes discussion of drills developed for horizontal drilling 
 underground. Comprehensive coverage of all drills that may be used for 
 such purpose is not intended. 
 
 5 Reference to specific equipment, trade names, or manufacturers does not imply 
 endorsement by the Bureau of Mines. 
 
 FIGURE 1. - Handheld air drill, 
 
FIGURE 2. - Post-mounted electrohydraulic drill. 
 
 ry*r rp 
 
 Scale, feet 
 FIGURE 3. - Longyear horizontal drill. 
 
 smaller and more compact than the Longyear drill (fig. 5) was designed by the 
 Bureau and constructed by Lambert Drilling Co. Although the feed length is 
 limited to 2 feet, the Bureau's experience indicates that bit control during 
 drilling is not affected by frequent interruptions in drilling because of the 
 short feed length. A particular disadvantage of the Lambert drill is the slow 
 retraction after the spindle has been extended its maximum length. Some hori- 
 zontal boreholes have been drilled to 2,500 feet with no indications that the 
 drill had reached its capacity (10). Bit thrust potential of the drill is 
 34,000 pounds at 2,000 psi hydraulic pressure. The drill is equipped with 
 
FIGURE 4. - Longyear power unit. 
 
 FIGURE 5. - Lambert drill. 
 
gages to monitor bit thrust, torque, and rotational speed. Setting a drilling 
 angle is a simple adjustment because the drill head swivels through 360°. This 
 type of drill is presently marketed by Sprague and Henwood Co. , Scranton, Pa. 
 
 Both the Longyear and Lambert drills are cribbed during drilling to the 
 proper height and angle so that the horizontal borehole is started in about the 
 center of the coalbed and parallel to the bedding planes. In addition, the 
 drills are anchored to the coalbed to prevent backward movement of the drill 
 when high thrusts are being applied to the bit. At the start of drilling, a 
 6-inch-diameter hole is drilled to a depth of about 22 feet and a 4-inch casing 
 is then cemented in the hole. A gas-water separator that provides the means 
 for controlling methane during drilling is attached to the steel casing. 
 
 Much of the labor involved in cribbing and angling drills underground 
 becomes unnecessary with the drill equipment designed by Acker Drill Co. , Inc. , 
 and J. H. Fletcher and Co. (figs. 6-7) , which are similar to the drill designed 
 by Longyear. The feed frames of the Acker and Fletcher drills can be hydrau- 
 lically elevated above floor level and angled above or below the horizontal 
 plane automatically. Gas-water separators are also an integral part of the 
 drills. The drill carrier for the Acker and Fletcher drills are four-wheeled 
 vehicles and are hydraulically powered so that the equipment can be trammed. 
 
 All of the preceding drills have power units that can be separated from 
 the drill units by as much as 500 feet. The only connections between the drill 
 and power units are hydraulic hoses except for the Acker and Fletcher drills 
 which have Mine Safety and Health Administration (MSHA) permissible illumina- 
 tion. The hydraulic fluid is circulated by an electrically driven hydraulic 
 
 FIGURE 6. - Acker Drill Co. drill. 
 
FIGURE 7. - J. H. Fletcher and Co. drill. 
 
 pump from the reservoir on the power unit to the drill unit. Therefore, the 
 drills can be used in return airways while the power unit remains in fresh 
 air. The Acker, Fletcher, and Lambert drills are equipped with hydraulic 
 chucks that greatly reduce the time of chucking and pipe pulling operations. 
 
 Longyear, Inc. , designed a second electrohydraulic drill with the drill 
 and permissible power unit mounted on the same frame (fig. 8). Because the 
 drill unit cannot be separated from the power unit, its use is limited to 
 intake air and face areas except in States where permissible equipment can be 
 operated in return airways. The drill is a smaller version of the first drill 
 Longyear designed (fig. 3); feed length is only 6 feet compared with the 
 11-foot length of the first drill. The drill is equipped with a hydraulic 
 chuck and gages to monitor bit thrust, torque, and rotational speed. 
 
FIGURE 8. - Longyear Drill Co. drill, 
 
 Other drills that can be used to drill horizontal boreholes are manufac- 
 tured in Europe and marketed in the United States. These drills are electro- 
 hydraulic, smaller and lighter than the preceding five drills, and generally 
 are mounted on posts. In Europe, these drills are used to drill methane 
 drainage holes into strata above the mined coalbed. The Victor Minotaur drill 
 (fig. 9) marketed by Dowty Corp., Pittsburgh, Pa., the Boyles Bros. Model HNH 
 drill (fig. 10) marketed by Dresser Industries, Inc., Dallas, Tex., and the 
 Atlas Copco Diamec 250 drill (fig. 11) marketed by Christensen Diamond 
 Products, Salt Lake City, Utah, are similar in construction. Each has a drill 
 head that is mounted on a feed frame. The feed length ranges from 2.5 feet 
 for the Victor drill to 5 feet for the Atlas Copco and to 7 feet for the 
 Boyles 1 drill. The Atlas Copco drill will probably require modification 
 before it can be used routinely for drilling in coalbeds because the thrust 
 and rotation cannot be controlled independently; such control is essential 
 for change in bit inclination. For ease in underground maneuvering, each of 
 these drills can be fitted with axles and wheels. 
 
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 Horizontal drilling technology has been developed by the Bureau to the 
 point where lengths of 1,000 feet are easily attained (12). In some cases, 
 holes have been drilled to 2,100 feet, but with difficulty (4). Surveying 
 to determine bit angle is an important part of horizontal drilling. Bore- 
 holes should be surveyed at least every 20 feet to determine bit inclination. 
 If the bit begins to deviate from its programmed trajectory, bit thrust and 
 rotational speed must be changed to keep the bit within the coalbed. Bit 
 inclination can be determined using commercially available pumpdown equipment 
 such as the single-shot instruments by Sperry Sun and Eastman Well Surveying 
 Co. An in-hole cableless surveying unit is being developed by Ensco under 
 contract with the Bureau. 
 
 DRAINAGE AND CONTROL TECHNOLOGIES 
 
 Drainage of the large volumes of methane produced from horizontal holes 
 requires underground pipelines to transport methane to the surface. Under- 
 ground methane pipelines for gob gas have been used by the coal mining 
 industry in Germany since 1943 (1). After World War II, increased production 
 due to mechanization, and mining of deeper and gassier coalbeds, necessitated 
 methane drainage throughout European coalfields, where it now is a fully 
 integrated part of longwall mining (3) . 
 
 Most underground methane pipelines in the United States are experimental 
 and use both steel and plastic lines. Because of the risk of damage from roof 
 falls and bottom heaving, it is important to include a means of shutting off 
 the flow of methane from the drainage hole to prevent methane from escaping 
 from a damaged or faulty pipeline. Automatic shut-in of each horizontal hole 
 is accomplished by means of a spring-loaded ball valve (normally closed) that 
 is held open with 55 psig of compressed air (fig. 12) supplied by a small 
 compressor (1 cfm, 50 psig). Compressed air is piped to the pneumatic valve 
 for each hole through brittle polyvinyl chloride (PVC) pipe strapped to the 
 top of the pipeline along its entire length (fig. 13). Methane sensing and 
 control systems, which are commercially available, vent the compressed air 
 line and consequently close the pneumatic valves should abnormal methane con- 
 centrations be detected. The pneumatic valves close automatically when a 
 sensor malfunctions, when an electrical line to a sensor is cut or broken, or 
 when the PVC pipe is broken by a roof fall. Requirements for underground 
 methane pipelines will vary depending upon the type of pipe, the location of 
 the pipeline, and the amount of methane gas transported. Guidelines for 
 installation, maintenance, and safe operation of underground pipelines have 
 been developed by the Bureau (16) and MSHA (15). 
 
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 FIGURE 13. - Steel pipeline, 3/4-inch PVC pipe, sensor head. 
 
14 
 
 EXPERIENCE WITH HORIZONTAL DRILLING 
 
 Since the characteristics of different coalbeds vary, the parameters used 
 for horizontal drilling may also vary. Therefore, using horizontal boreholes, 
 the Bureau is conducting field demonstrations in cooperation with operators of 
 mines located in areas not previously degasified. 
 
 Over the past 5 years, industry interest in methane drainage has grown and 
 is expected to accelerate in the next 5 years with the development of horizon- 
 tal drilling technology, longhole drill equipment, methane sensing. and control 
 systems, and guidelines for installing, maintaining, and operating underground 
 pipelines. In addition, the demonstration projects have shown that large 
 volumes of methane can be removed from coalbeds with up to 70 pet reduction of 
 methane flows as the degasified zone is mined (5, 10, 13). 
 
 Pittsburgh Coalbed, Pa. and W. Va. 
 
 Much of the initial degasif ication work by the Bureau of Mines on degasifi- 
 cation of coalbeds was done in the Pittsburgh coalbed. The most recent project 
 was the drilling of four long, horizontal boreholes into virgin coal in Bethle- 
 hem Mines Corp. 's Marianna No. 58 mine. The total length of the holes drilled 
 was about 5,700 feet; one hole was 2,500 feet long. After 500 days, more than 
 100 MMcf of methane had been removed from the coalbed. Preliminary results 
 indicate that methane emissions from the face area were reduced by 80 pet. 
 Bethlehem Mines Corp. is currently investigating the possibility of applying 
 methane drainage to other mines using similar techniques. 
 
 Eastern Associated Coal Corp. is experimenting in the Federal No. 2 mine 
 with a tunnel-boring machine that is driving an entry 6,000 feet into virgin 
 coal. Although the advance rate of the tunnel has been slow and consequently 
 methane problems have been minimal, horizontal drainage holes are being 
 drilled in advance of the machine to control methane flows at the face of the 
 tunnel. Boreholes are drilled to about 1,000 feet with a Longyear electro- 
 hydraulic drill (fig. 8). Longyear designed the drill for drilling in limited 
 space and, consequently, the drill and power units are mounted in line on a 
 single frame. The feed length is about 6 feet and the total length of the 
 drill unit is about 12 feet. Drilling is conducted on intake air only. 
 
 Consolidation Coal Co. (Consol) has experimented with both rotary and non- 
 rotary horizontal drilling techniques. While the Bureau uses only a rotating 
 drill string (4) , Consol developed a nonrotating drill string with a downhole 
 drill motor and a patented deflection device. Consol claims this technique 
 provides more positive control of borehole deviation, both vertically and 
 laterally and that it appears to be faster although somewhat more difficult to 
 operate. The company has designed and developed a mobile horizontal drill rig 
 and a borehole survey instrument (14). The survey instrument not only measures 
 the pitch and roll of the bit, but also the azimuth of the borehole and the 
 thickness of the coalbed ahead of mining (14). The drilling system has drilled 
 more than 20,000 feet of horizontal boreholes to reduce methane face emissions 
 in advancing sections. Horizontal boreholes 1,000 feet long are routinely com- 
 pleted in eight working shifts including setup time. The greatest effect of 
 
15 
 
 boreholes drilled in advance of mining is in face areas, where up to 68 pet 
 decline in methane concentrations is reported. Methane flows in the returns 
 were reduced by 50 pet (14). 
 
 Lykes Resources, Inc., is planning an extensive methane drainage program 
 at the newly opened Emerald mine located in Waynesburg, Pa. Underground 
 degasification will be conducted with Acker Drilling Co. 's "Big John" drill 
 (fig. 6). Methane from the horizontal holes will be transported to the surface 
 using a polyethylene pipeline. Drilling techniques will be similar to those 
 developed by the Bureau in earlier studies. 
 
 Sunnyside Coalbed, Utah 
 
 Kaiser Steel Corp. is currently working with the Bureau of Mines on 
 degasifying an area of coal at its Sunnyside No. 1 mine that will not be mined 
 for 2 or 3 years. Two horizontal boreholes (9) 500 feet long have removed 
 60 MMcf of methane over a 16-month period. Bureau personnel will begin the 
 drilling of three long horizontal boreholes at the end of 1979. The methane 
 will be carried through a pipeline to the surface where it will be burned in 
 the mine's coal cleaning plant. Kaiser Steel Corp. is planning to continue 
 the drilling program if results are successful. 
 
 Beckley Coalbed, W. Va. 
 
 A recent drilling program was conducted by the Bureau of Mines and the 
 Maple- Mining Co. at the Maple Meadow mine in the Beckley coalbed in southern 
 West Virginia. Eight holes, with a total length of 4,850 feet, were recently 
 drilled from the bottom of a 24-foot-diameter ventilation shaft that was sunk 
 3 years in advance of mining. Results from the project are not yet available 
 since the drilling was only recently completed, although methane drainage 
 rates are low because the shaft bottom is located in a synclinal area that is 
 draining water from a large area of the coalbed. 
 
 Mary Lee and "Blue Creek" Coalbeds, Ala. 
 
 Jim Walter Resources, Inc. , is presently working with the Bureau of Mines 
 on investigating longhole drilling to intercept methane flows in the Mary Lee 
 and "Blue Creek" coalbeds. Several short holes were drilled in mines No. 3 
 and 4, located near Birmingham, Ala. The coalbed is highly fractured, and may 
 be under local stress resulting in holes caving immediately after drilling. 
 Attempts are now being made to guide long horizontal boreholes into specific 
 heights of the upper or lower portion of the coalbed. A successful hole, 
 1,000 feet deep, has recently been drilled in the lower portion of the coalbed 
 with a resulting initial methane flow of 200,000 cfd. If further tests are 
 successful, the mine plans to initiate its own drilling program. The mine 
 operators are requesting approval to use a polyethylene pipeline to transport 
 the methane to the vertical drill hole for subsequent sale or utilization. An 
 Acker "Big John" drill unit will be used for the drilling program. 
 
 United States Steel Corp. has been drilling horizontal boreholes to inter- 
 cept methane flows at the Oak Grove mine near Birmingham, Ala. , since 1976. 
 
16 
 
 Fifteen holes have been drilled in the Blue Creek coalbed; the longest hole is 
 1,040 feet. Drilling rates have ranged from 15 to 115 feet per 5-hour shift. 
 The drill unit used is a Joy face-type that was modified by Acker Drill Co. 
 Control of the bit path is similar to the method developed by the Bureau of 
 Mines. 
 
 The gas drained by the holes is transported to the surface through a 
 steel pipeline. Gas flows have been reported as high as 100,000 cfd from a 
 1,000-foot hole. 
 
 Pocahontas No. 3 Coalbed, Va. 
 
 Preliminary tests have been conducted in the Pocahontas No. 3 coalbed by 
 Island Creek Coal Co. at the Virginia Pocahontas No. 5 mine to determine the 
 effectiveness of methane drainage techniques in advance of mining. Horizontal 
 boreholes were drilled to depths of 500 feet into virgin coal. As mining 
 advanced into the degasified zone, tests indicated substantially less quantities 
 of methane than in other areas of the mine. The company has purchased an 
 Acker drill unit and has successfully drilled several horizontal boreholes to 
 depths of over 1,000 feet in approximately seven shifts, not counting setup 
 time. The methane produced from the horizontal boreholes is transported to 
 the surface through an underground plastic pipeline (17). 
 
 Hartshorne Coalbed, Okla. 
 
 Since 1975 Ker-McGee Corp. has been drilling long horizontal boreholes at 
 the Choctaw mine in Stigler, Okla. , to drain methane from the Hartshorne coal- 
 bed. Boreholes have been drilled successfully to 3,000 feet using in-hole 
 motors. Approximately 20 horizontal boreholes have already been completed and 
 an additional 20 holes are being planned. Cumulative gas flow rates as high 
 as 2 MMcf per day have been reported. 
 
 "B" Seam, Colo. 
 
 Mid-Continent Coal and Coke Corp. is removing methane from gob areas of 
 an advancing longwall in the Dutch Creek mine located at Carbondale, Colo. , 
 by drilling holes into overlying strata ( 11) . The 2-inch-diameter boreholes 
 are drilled to 150 feet on 50-foot centers. An EDECO minihydrac drill is 
 used to drill the holes at an inclination of 60°. The gas is transported to 
 the surface through a 6,000-foot pipeline. Vacuum is applied to the boreholes 
 by Nash vacuum pumps that are located on the surface. This method of methane 
 drainage is patterned after methods used in Great Britain and Europe where 
 advancing longwall mining is common. 
 
 SUMMARY 
 
 The Bureau of Mines has shown through field demonstrations that horizon- 
 tal boreholes drilled into the coalbed are an effective method of intercepting 
 methane flows. As a result of research and development efforts by the Bureau 
 and industry, equipment for drilling from underground locations is now avail- 
 able from commercial sources. Drilling long horizontal boreholes can now be 
 
17 
 
 accomplished in most coalbeds. The equipment needed to safely transport the 
 methane to the surface is also commercially available. Publications by the 
 Bureau are cited that discuss how to drill horizontally in coalbeds and how 
 to safely handle the methane. 
 
 As deeper coalbeds are mined, the need for advance methane drainage will 
 become a necessity instead of an option. Proper planning in the early stages, 
 long before the mine is opened, will result not only in a safer work environ- 
 ment, but in a potentially more profitable operation by reducing ventilation 
 costs and increasing production. 
 
REFERENCES 
 
 1. Bromilow, J. C. , and J. H. Jones. Drainage and Utilization of Fire Damp. 
 
 Colliery Eng. , v. 32, No. 6, June 1955, pp. 222-232. 
 
 2. Cervik, J. Behavior of Coal-Gas Reservoirs. BuMines TPR 10, 1969, 10 pp. 
 
 3. . Methane Control in Longwalls--European and U.S. Practices. Pres. 
 
 at SME-AIME Ann. Meeting, New Orleans, La., Feb. 18-22, 1979; available 
 for consultation at Pittsburgh Research Center, Bureau of Mines, 
 Pittsburgh, Pa. 
 
 4. Cervik, J., H. H. Fields, and G. N. Aul. Rotary Drilling Holes in Coal- 
 
 beds for Degasification. BuMines RI 8097, 1975, 21 pp. 
 
 5. Fields, H. H. , J. Cervik, and T. W. Goodman. Degasification and Produc- 
 
 tion of Natural Gas From an Air Shaft in the Pittsburgh Coalbed. 
 BuMines RI 8173, 1976, 23 pp. 
 
 6. Fields, H. H. , S. -Krickovic, A. Sainato, and M. G. Zabetakis. Degasifi- 
 
 cation of Virgin Pittsburgh Coalbed Through a Large Borehole. BuMines 
 RI 7800, 1973, 27 pp. 
 
 7. Hadden, J. D. , and J. Cervik. Design and Development of Drill Equipment. 
 
 BuMines TPR 11, 1969, 11 pp. 
 
 8. Kim, A. G. , and L. J. Douglas. Hydrocarbon Gases Produced in a Simulated 
 
 Swamp Environment. BuMines RI 7690, 1972, 15 pp. 
 
 9. Perry, J. H. , G. N. Aul, and J. Cervik. Methane Drainage Study in the 
 
 Sunnyside Coalbed, Utah. BuMines RI 8323, 1978, 11 pp. 
 
 10. Prosser, L. J. , Jr. , G. L. Finfinger, and J. Cervik. Methane Drainage 
 
 at the Marianna No. 58 Mine Using Horizontal Boreholes, 1978, 46 pp.; 
 available for consultation at Pittsburgh Research Center, Bureau of 
 Mines, Pittsburgh, Pa. 
 
 11. Reeves, J. A. , Jr. Advancing Longwall Mining at Mid-Continent. Am. Min. 
 
 Cong. J., v. 64, No. 7, July 1978, pp. 25-29. 
 
 12. Rommel, R. R. , and L. A. Rives. Advanced Techniques for Drilling 1 ,000 Ft 
 
 Small Diameter Horizontal Holes in a Coal Seam. Volume 1 (Contract No. 
 H0111355). BuMines Open File Rept. 17(l)-76, 1973, 109 pp.; available 
 for consultation at Bureau of Mines facilities in Denver, Colo. , 
 Twin Cities, Minn., Pittsburgh, Pa., and Spokane, Wash.; U.S. Department 
 of Energy facility in Morgantown, W. Va. ; National Library of Natural 
 Resources, U.S. Department of the Interior, Washington, D. C. ; and 
 National Technical Information Service, U.S. Department of Commerce, 
 Springfield, Va. , PB 249 714/AS. 
 
19 
 
 13. Thakur, P. C. , and J. G. Davis. How to Plan for Methane Control in Under- 
 
 ground Mines. Min. Eng. , v. 29, October 1977, pp. 41-45. 
 
 14. Thakur, P. C. , and W. N. Poundstone. Horizontal Drilling Technology for 
 
 Advance Degasification. Pres. at SME-AIME Ann. Meeting, New Orleans, 
 La., Feb. 18-22 , 1979 ; available for consultation at Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, Pa. 
 
 15. Tisdale, J. E. , D. W. Mitchell, R. A. Elam, M. J. Lawless, and B. E. Tayler. 
 
 Piping Methane in Underground Coal Mines. MSHA IR 1094, 1978, 34 pp. 
 
 16. Tongue, D. W. , D. D. Schuster, R. Niedbala, and D. M. Bondurant. Design 
 
 and Recommended Specifications for a Safe Methane Gas Piping System 
 (Contract No. J0155145) . BuMines Open File Rept. 109-76, 1976, 97 pp.; 
 available for consultation at Bureau of Mines facilities in Denver, 
 Colo., Twin Cities, Minn., Pittsburgh, Pa., and Spokane, Wash.; 
 U.S. Department of Energy facilities in Morgantown, W. Va. ; National 
 Library of Natural Resources, U.S. Department of the Interior, 
 Washington, D. C. ; and National Technical Information Service, U.S. 
 Department of Commerce, Springfield, Va. , PB J0155145. 
 
 17. Von Schonfeldt, Hilmar. Methane Recovery From Deep Seams. Pres. at 
 
 Methane Recovery From Coalbeds Symp. , Pittsburgh, Pa. , Apr. 18-20, 
 1979; available for consultation at Pittsburgh Research Center, 
 Bureau of Mines, Pittsburgh, Pa. 
 
20 
 
 APPENDIX. --DRILL UNITS 
 
 1. Acker Drill 
 
 Acker Drill Co. , Inc. 
 
 Box 830 
 
 Scranton, Pa. 18501 
 
 2. Atlas Copco Drill 
 
 Chris tensen Diamond Products 
 P.O. Box 41136 
 2215 Distributor's Dr. 
 Park Fletcher 
 Indianapolis, Ind. 46241 
 
 3. Dresser Drill 
 
 Dresser Industries, Inc. 
 P.O. Box 1879 
 Columbus, Ohio 43216 
 
 4. Longyear Drill 
 
 Longyear Co. 
 
 925 Delaware St., S.E. 
 
 Minneapolis, Minn. 55414 
 
 5. Fletcher Drill 
 
 J. H. Fletcher and Co. 
 P.O. Box 2143 
 Huntington, W. Va. 25722 
 
 6. Lambert Drill 
 
 Sprague and Henwood, Inc. 
 221 West Olive St. 
 Scranton, Pa. 18501 
 
 7. Victor Drill 
 
 Dowty Corp. 
 
 Progress St. 
 
 Cranberry Industrial Park 
 
 Zelienople, Pa. 16063 
 
 PC-i 3 7 
 
 *U.S. GOVERNMENT PRINTING OFFICE: 1980-603-102/86 int.-bu.of mines,pgh.,pa. 24806 
 
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 32084 
 
 
 
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LIBRARY OF 
 
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