RII 8640 I 

Bureau of Mines Report of lnvestigations/l982 

Drilling a Horizontal Coalbed Methane 

Drainage System From a Directional 

Surface Borehole 

By David C. Oyler and William P. Diamond 

UNITED STATES DEPARTMENT OF THE INTERIOR 
Report of Investigations 8640 

Drilling a Horizontal Coalbed Methane 

Drainage System From a Directional 

Surface Borehole 

By David C. Oyler and William P. Diamond 

UNITED STATES DEPARTMENT OF THE INTERIOR 

James G. Watt, Secretary 

BUREAU OF MINES 

Robert C. Horton, Director 
This publication has been cataloged as follows : 

Oyler, D. C. (David C.) 

Drilling a horizontal coalbed methane drainage system from a 

directional surface borehole. 

(Rcport of invcstigations / Burcau of Mincs ; 8640) 

Includcs bibliographical rcfcrcnccs. 

Supt. of l)ocs. no.: I 28.23:8(,40. 

1. Minc gascs. 2. Mcthanc. 3. Coal rnincs and mining-Safcty mcasurcs. 4. Boring. I. Diamond, W. P. (William P.). 11. Titlc. 111. Scrics: 

Rcport of invcstigations (Unitcd Statcs. Burcau of Mines) ; 8(,(,0. 
CONTENTS 

Page 

Abstract ........................................................................ Background and introduction ..................................................... Acknowledgments ................................................................. Drilling program ................................................................ General drilling plan ...................................................... Site selection and preparation ............................................. Drilling rig ............................................................... Pilot hole drilling ........................................................ Directional drilling equipment and control techniques ................. Drilling rates and bit performance .................................... Drilling sunmary ...................................................... Reaming .................................................................... Lost circulation ...................................................... Fishing operations .................................................... Reaming with a stinger assembly ....................................... Drilling summary ...................................................... Casing and cementing ....................................................... Horizontal drilling ........................................................ Horizontal hole H1 .................................................... Horizontal hole H2 .................................................... Horizontal hole H3 .................................................... Horizontal holes H4 and H5 ............................................ Reaming horizontal sump ............................................... Completion work and initial production rates ............................... Project costs ................................................................... Detailed cost analysis ..................................................... Project cost summary ....................................................... Estimated costs for a production directional hole .......................... Conclusions and recommendations ................................................. Horizontal drilling ...............ee.e.....e....ee......................... 

Reaming ............e..ee....................e...e........................e. 

Bits ....................................................................... Appendix A*--EM-19. detailed time breakdown of drilling operations .............. Appendix B.-- Project chronology ................................................. 

ILLUSTRATIONS 

Map of project site ........................................................ Section view of EM-19 well path ............................................ Drilling site before preparation ........................................... Drilling location after site preparation ................................... Plan view of EM-19 drilling site ........................................... Drilling rig ............................................................... Dyna-Drill tool and drilling assembly ...................................... Strata-Pax bit ............................................................. Diamond bit ................................................................ Mixing Dextrid-Polymer mud for pilot hole drilling ......................... Reaming bits ............................................................... Flat-faced Strata-Pax reamer and stinger ................................... Television camera .......................................................... Debris fished from EM-19 ................................................... Bit-crown fishing spear .................................................... 
ILLUSTRATIONS.. Continued 

Page 

Reaming stinger and diamond reaming hit .................................... Plan and section views of geometry of EM-19 near the bottom of casing ...... Plan view of horizontal holes and bottom hole locations of monitor holes ... Two methods of following the coalbed ....................................... Casing underreamer ......................................................... EM-19 surface installation .......eeeee..eeeeeeeee.eeeeeeeeee.eeeee.eeee.eee 

Dewatering hole EM-20 ..............e..eeeeeee.eeeeeeeeee.eeeeeeeeeeeeeeeeee 

Production data from EM-19 and EM-20 ....................................... Crew running the submersible pump into EM-19 ............................... Shale and coal blown out of EM-19 .......................................... 

TABLES 

Penetration versus drilling parameters (pilot hole) ........................ Selected penetration rates versus formation types .......................... Bit costs-- pilot and horizontal hole^..............^^^^^^.^^^^^^^^^^..^^^^^ 

Bit costs--reaming .....eee..eeee...e.e..e.eee.eeeee..e..eeeeee....eeeeee.ee 

Horizontal distances drilled ............e..eeeeeee.e.eeeee.eeeee.eeee.ee.e. 

Directional hole (EM-19) drilling cost^..............^.^^.^^^.^..^^^^^^^^^^ 

Costs for EM-19 drilling operations ........................................ Project cost totals ........................................................ Production hole time estimate .............................................. Production hole cost estimate .............................................. 
DRILLING A HORIZONTAL COALBED METHANE DRAINAGE SYSTEM 

FROM A DIRECTIONAL SURFACE BOREHOLE 

by 

David C. Oyler 1 and William P. Diamond 2 

ABSTRACT 

Three long horizontal holes were 

drilled from a directionally drilled surface hole at the Emerald Mine near 

Waynesburg, Pa. The purpose was to adapt 

the technique of directional drilling for 

use in draining methane from coalbeds. A 

504-m (1,652-ft) long, 76-mn (3-in) diameter, circular arc pilot hole was 

drilled, using a downhole mud motor, to 

enter the Pittsburgh coalbed at a vertical depth of 305 m (1,000 ft). The hole 

was reamed to 222 nm (8-3/4 in) and was 

cased to a measured depth of 486 rn 

(1,595 ft). Three 76-nn (3-in) diameter 

horizontal drainage holes were then 

drilled, totaling 2,909 n (9,544 ft) 

of horizontal hole. Improvements in 

drilling nethods increased the average 

drilling rate from 20.4 n (67 ft) to 

64.9 m (213 ft) per day. The cost of 

drilling the directional and horizontal 

holes (using a Governnent-owned drill 

rig) was $1,169,530, a figure inflated by 

inexperience and by delays caused by 

lost-circulat ion problems and fishing 

operations. An estimated total drilling 

cost of $960,000 (including rental of a 

drill rig) for an improved system, was 

determined by a detailed cost analysis. 

Initial gas and water production 

from November 1979 through May 1980 was 

low because of caving of the horizontal 

holes drilled in shale near the bottom of 

the casing. 

BACKGROUND AND INTRODUCTION 

A project to directionally drill a 

coalbed methane drainage systen fron the 

surface was initiated by the Bureau of 

Mines in 1976. Drilling activities began 

in September 1978 at the Emerald Mine in 

Greene County, Pa. (fig. 1). In October 

1977, the contract was transferred to the 

U.S. Department of Energy, with the 

Bureau of Mines continuing technical 

management of the project. Included in 

I~echanical engineer. 

2~uDerv isory geologist. 

All authors are with the Pittsburgh Research Center, Bureau of Mines, Pittsburgh, Pa. 

the nethane drainage systen was a directionally drilled access hole from the 

surface intercepting the Pittsburgh coalbed, three long horizontal inethane collection holes drilled in the coal, a vertical hole for removing water from the 

coalbed, and seven vertical holes to nonitor the effects of the systen with time. 

The goals of the project are to demonstrate that the technique of directional 

drilling can be used to drain nethane 

fron coalbeds in advance of mining, to 

determine the distance horizontal holes 

can be drilled, to obtain information 

to improve the technique, and to invest igate coalbed reservoir mechanics. 
Scale 

FIGURE 1. - Map of proiect site. The path of EM-19 and the locations of dewatering hole EM-20, 

monitor holes EM-21 through EM-27, and nearby mine workings are shown. 

Previous publications3 have outlined in the work at the Emerald Mine and to make 

detail the scope and goals of this and recommendations for improvements in 

other Bureau of Mines directional drill- drilling methods for future systems of 

ing research. The purpose of this report this type. 

is to describe the actual performance of 

- 3~iamond, W. P., and D. C. Oyler. Directional Drillinq for Coalbed Degasification 

in Advance of Mining. proc. 2d Ann. Sym~. on Methane Recoverv From Coalbeds, 

Pittsburgh, Pa., Apr. 18-20, 1979, DD. 162-176. 

. Drilling Long Horizontal Coalhed Methane nrainaqe Holes From a Directional 

Surface Rorehole. eroc. 1st Ann. SPE/DOE Svrnp. on TJnconventional Gas Recovery, 

Pittsburgh, Pa., Yay 18-21, 1980, pp. 325-378. 

Diamond, W. P., D. C. Oyler, and H. H. Fields. Directionally Controlled Drillinq To 

Horizontally Intercept Selected Strata, Upper Freeport Coalbed, Greene County, 

Pa. SuMines RI 8231, 1977, 21 pp. 

Oyler, D. C., Y. P. Diamond, and P. W. Jeran. Directional Drillinq for Coalbed 

Deqasification: Proqram Goals and Proqress in 1979. BuMines RI 8380, 1979, 15 pp. 
HORIZONTDL DISTDNCE, fl 

4WIIII,/IIII 1.100 lpa0 900 so0 700 MK) 500 400 Xa 200 100 0 

Site Selection and Preparation 

400 - The primary requirement of a directional drilling site is for sufficient 

depth of cover over the target coalbed to 

nake the required 1.57-rad (90') turn 

Ic5 m-mnrrtm 

to enter the coalbed horizontally. At 

YJ rr rroq rm the rate of angle build desired for C ma TL~Y rhk 

5 shah llmlm the directional hole, 0.34 rad/100m 

-" $ (6'1 100 ft), the required distance was 

290 m (950 ft). The drilling site 

selected was at the top of the highest 

ridge in the area to obtain the required 

- 600 depth of cover. The local structure of 

the coalbed was also downdip in the -500 direction of drilling which added another - 400 6 m (20 ft) to the effective vertical 

distance. The actual vertical distance 

to the coalbed, determined when well EMpossible to start drilling with the rig's FIGURE 2. - Section view of EM-19 well path. mast vertical (a definite advantage durGeologic column at left is from a ing drilling and for servicing the well) 

corehole near well EM-20. and left an additional 15 m (50 ft) to be 

53 I 1 I I 1 ZW 20 (fig. 1) was drilled, was approxi- 350 300 250 230 lyl 100 50 0 

H~m~AL mViwE. rn mately 305 m (1,000 ft). This made it 
FIGURE 3. - Drilling site before preparation. Photograph taken March 1978, view is east. 
approximately 120 m (400 ft) by 45 n 

(150 ft). A divided mud pit 26 m (85 it) 

long, 6 m wide (20 ft), and 2 m (6 ft) 

deep was then dug. The site was then 

covered by about 30 cm (1 ft) of crushed 

stone which was rolled and compacted. 

Figure 4 shows the site in August 1978 

shortly after the preparation work was 

completed. A plan view of the site, 

after the drilling equipment was set up 

in November 1978, is shown in figure 5. 

A najor difficulty with the EM-19 

drilling site, which will be discussed in 

nore detail in the "Pilot Hole Drilling" 

and "Reaming" sections, was the ridgetop 

location which put the site above the 

local water table. Several fractured and 

solution channeled limestones became 

severe lost circulation zones that created najor difficulties in drilling until 

the hole was finally cased. 
FIGURE 5. - Plan view of EM-19 drilling site. 

Drilling Rig ----- 

The drilling rig used to drill the 

directional hole was a Reed Tool Co. 

exploratory rig4 (fig. 6). The r Lg is 

hydraulically operated, and powered by a 

Cummins model NT-855-P380, 283-kW (380- 

hp) diesel engine. The rig has two hoist 

cylinders giving it a 311-kN (70,000-lb) 

hoist capacity, and a 10.5-m (35-ft) 

stroke. It was originally purchased in 

1974 for the Bureau of Mine's Mather 

directional hole project .5 

The primary requirements for the 

drilling rig were a 10.5-n (35-ft) 

--- 4~eference to specific equipment, trade 

names, or manufacturers does not imply 

endorsement by the Bureau of Mines. 

'~hird work cited in footnote 3. 

stroke, an ability to finely adjust the 

drill pipe feed rate and hit weight, and 

a "pulldown" capacity (the ability to put 

additional weight on the bit). The pulldown capacity is necessary to push casing 

through tight spots. The stroke length 

is required to handle casing and drill 

pipe for reaming. The fine feed capacity 

is needed when running downhole motors to 

prevent stalling and damaging the tools. 

Two other desirable features, which the 

Reed rig did not have, were tongs and 

breakout tools for handling large drill 

pipe and a wide drill table to allow easy 

handling of bits and subs greater than 

305 mrn (12 in) in diameter. This made it 

difficult to ream and case the hole to 

shut off the lost-circulation zones near 

the surface. 
FIGURE 6. - Drilling rig. Note survey tool and wireline hoist in right foreground. Photograph 

taken during pi lot hole drilling operation, November 1978. 

- Pilot Hole Drilling ------ - 

The directional hole was begun by 

rotary drilling a 318m (12-1/2-in) 

diameter vertical surface hole to the top 

of bedrock and installing 3.7 m (12 ft) 

of 267-mn (10-112-in) diameter conductor 

pipe. A 159-mm (6-114-in) diameter tricone rock bit was then used to rotary 

drill the hole to 15 m (50 ft) where 

directional drilling was to begin. 

Directional Drilling Equipment 

and Control Techniques 

The directional drilling was done 

using a 60-mm (2-318-in) diameter DynaDrill tool, a 76-mm (3-in) diameter bit, 

and 56-mn (2-3/ 16-in) 0.d. BQ wireline 

drill rod (3.3-m (10-ft) joints). The 

Dyna-Drill (fig. 7) is a positive displacement motor with a helical drive 

shaft that rotates when fluid is pumped 

through the tool. Rotation of the drive 

shaft is transmitted through universal 

joints to the shaft of a hit sub. Sealed 

bearings support the shaft of the bit 

sub. The housing of this sub is also 

bent at a small angle to provide directional control. Both the universal 

joints and bearings are expendable items, 

typically requiring replacement at 50- 

to 100-h intervals. Drilling fluid was 

supplied to the tool hy two FWI 5P-200A 

quintuplex pumps. 

The Dyna-Drill will build angle at a 

rate roughly proportional to the size of 

the bend of the housing. The rate is 

also affected to some extent by the type 
fi - Standoff ring 

- 

Bent housing and 

connecting rod assembly 

Nonmagnetic 

drill rod 

I- Bearing and drive 

shaft assembly Bp Rotating bit sub 

- 

0- 

- 

a- Diamond plug bit 

Muleshoe sub 

Bypass valve 

FIGURE 7. - Dyna-Dri ll tool and 

dri l ling assembly. 

Motor assembly 

of formation drilled, the hole inclination, the orientation of the bend, and 

the weight on the bit. During the Mather 

directional drilling project ,6 the rate 

of angle build was controlled primarily 

by weight on the bit as determined by the 

pump pressure. (As bit weight increases, 

the differential pressure across the 

water courses of the bit increases.) 

Changes in weight on the bit also affect 

the penetration. When rapid angle build 

rates are desired, bit weight can be high 

and penetration is satisfactory. But 

when the angle build rate must be reduced, then the bit weight must be 

decreased and the penetration decreases. 

To eliminate the loss of penetration 

caused by decreased bit weight, the pilot 

hole at the Emerald Mine was controlled 

primarily by changing bent housings. 

Four assemblies were used. In order of 

increasing build rate capability they 

were a 0.0087-rad (30-min) bent housing, 

a 0.013-rad (45-nin) housing, and both of 

these housings with standoff rings added. 

The values of the angles are nominal values. The true bend of a particular housing often varied from its stated angle. 

By using different bends instead of varying the bit weight, it was possible to 

use the most efficient bit weights (measured by the pump pressures) and flow 

rates through the Dyna-Drill to obtain 

the maximum penetration rate (it also 

made it possible to correlate penetration 

rates to formation types). 

To minimize the number of trips 

made to change bent housings, the 

directional drilling engineer continually 

made projections of the well path. In 

this way it was possible to determine the 

effect a particular assembly would have 

on the well path and to plan the use of 

future housings to make corrections to 

bring the hole back on course. For example, if one assembly built angle at 

0.40 rad/100 rn (7'/100 ft) it might be 

used for 30 m (100 ft) and then a housing 

that gave a lower build rate would be 

used to bring the hole back on line, or 

'~hird work cited in footnote 3. 
slightly below it. The high-build housing would then be put back on and the cycle begun again. 

The actual position of the hole and 

the direction of the bend were determined 

by the use of a small-diameter magnetic 

singleshot surveying tool. This tool is 

run on a wireline and contains a conpass 

on a pivot and a camera to allow the azimuth of a reference point in the tool and 

the tool inclination to be recorded on 

film. A sllbassembly in the drill string 

with a pin in it and a cam on the survey 

tool (known as a muleshoe) forces the 

survey tool to line up in the same relative orientation with the drill string on 

each survey. This makes it possible to 

use the survey tool to aline the bent 

housing in the desired direction. 

Because the singleshot tool has a compass, it must be used with nonmagnetic 

drill pipe. The bottom 24 m (80 ft) of 

BQ rod was made of nonmagnetic stainless steel as were the housings of the 

Dyna-Drills. 

The output of the singleshot tool is 

(1) a reading of the well path azimuth, 

(2) the hole inclination, and (3) the 

azimuth of the drill string reference 

point. Given the position of the previous survey point, the new neasured depth, 

and items 1 and 2, the hole position can 

be determined trigonometrically. The 

survey positions in EM-19 were computed 

by the radius-of -curvature method. The 

drill string reference information allows 

the drill string to be properly oriented 

to keep the hole along the proper well 

path. 

During the course of drilling the 

directional drilling engineer determined 

the characteristics of each bent housing 

assembly in an attempt to find one that 

would give as close to a 0.34-rad/100 m 

(6'1 100 ft) build rate as possible. In 

general, it was found that no assembly 

gave this angle-build rate, so the occasional changing of housings was required. 

However, it was often possible to program 

the drilling so that housings were 

changed when a bearing package or universal joint had reached the end of its 

useful life or when a pipe trip was 

required for sonie other reason. This 

constant preplanning of the drilling, the 

use of gradual. hole corrections, and the 

method of allowing each housiqg to build 

angle at its natural rate actually reduced the "doglegs" (sharp angle changes) 

in EM-19 compared to directional holes 

drilled previously. Of the 16 pipe trips 

made during pilot hole drilling, 4 were 

made because of lost circulation, 5 because of Dyna-Drill failures, and 

2 because of failures of other equipment. 

The renaining five trips were made exclusively to change bent housings. However, 

a total of 10 changes of housings were 

made, so that the housing changes were 

doubled up with other operations about 

one-half of the time. 

The EM-19 pilot hole was drilled 

without sidetracks or plugbacks being required by the hole going off course. 

There was only one section of hole with 

severe doglegs. This took place from 

330 to 355 m (1,085-1,165 ft) measured 

depth (MD) (fig. 2) and was caused by the 

backoff and rotation of a joint of the BQ 

drill pipe above the Dyna-Drill, which 

rotated the Dyna-Drill tool face. This 

portion of the hole was drilled off 

course between 331 and 343m (1,065- 

1,125 ft) MD and the subsequently required sharp well path correction caused 

the dogleg section to continue to 355 m 

(1,165 ft) MD. The doglegs in this section ran fron 0.57 to 0.80 rad/100 m 

(10"-14'/100 ft). Fortunately, no problems were encountered either in reaning 

the hole or in running casing through 

this section of the hole. 
FIGURE 8. - Strata-Pax bit, 76-mm (3-in), type 128181. Bit length 15 cm (5.9 in). 

Drilling Rates and Bit Performance 

Because of the control techniques 

used, it was possible to determine and 

then stay at the optimum flow rate and 

pump pressure through the Dyna-Drill tool 

to give the maximum drilling rate. Early 

in the drilling operation it was found 

that the 5. 5-m3/h (24-gallmin) and 3,500- 

kPa (kilopascal) (500-lb/in2g) values 

recommended by the Dyna-Drill engineers 

were not the most efficient. Table 1 

shows the differences in penetration 

caused by varying pressure and flow rates 

through the tool. This table also conpares the performance characteristics of 

the two types of bits used to drill the 

pilot hole. The first Strata-Pax bit 

(a bit using tungsten carbide disks impregnated with diamond dust), (fig. 8) 

averaged 40.5 min/m (12.3 minlft) between 

15 and 135 m (50-442 ft) MD, with flow 

rates varying greatly from 5.5 to 13 m3/h 

(24-57 gallrnin), and pump pressures varying from 2,750 to 4,800 kPa (400-700 lb/ 

in2g). The most common flow rate during 

this period was 9.1 m3/h (40 gal/ min) 

and the most common pressure was 3,450 to 

4,100 kPa (500-600 1b/in2g). From 135 to 

162 m (422 to 530 ft) MD the parameters 

were held relatively constant at 

3,450 kPa (500 lb/im2g), and 5.5 to 

7.5 m3/h (24-33 (gal/min). This gave the 

lowest penetration rates experienced in 

all of the pilot hole drilling. The 

values of 9.5 n3/h (42 gal/nin) and 3,450 

to 8,900 kPa (500 to 900 ~b/in~~) were 

finally decided .upon as being the most 

efficient. 
TABLE 1. - Penetration versus drilling parameters (pilot hole) 

---- -~ole I Distance I ~mIverar- Average pump I 

Drilling 

interval 

-- 

First2.. . . . . . Second.. . . . . . ~hird 3. . . . . . . 

DIAMOND BIT. TYPE 147496. SN-8S540014 

STRATA-PAX BIT, TYPE 128181. SN-8~46823 

Fourth....... 

Total.. . 

Fifth.. . . . . . . 1 312-348 1 1,023-1,143 1 36 1 120 ( 607 1 16.9 1 5.1 1 6,200 1 900 1 

interval drilled 

15-135 

135-162 

162-28 1 

m 

281-312 

15-312 

ft 

--- 

drilled 

50- 442 

442- 530 

530- 923 

sixthb....... 

-- Total... 

'upon completion of drilling, face was worn but bit was in gage. 

2~lso drilled 6 m (20 ft) of concrete. 

ing 

time , min 

m 

923-1,023 

50-1,023 

STRATA-PAX BIT, TYPE 128181, SN-8S55183 

j0ne pax lost in this interval. 

ft 

125 

27 

120 

348-391 

Seventh.. . . . . ~i~hth~. .... . - Total... 

4~pon completion of drilling, bit was in nearly new condition. 

5~rimarily drilling limestone. 

drilling 

rate 

min/mImin/ft 

30 

303 

b~rimarily drilling coal and shale. 

pressure range 

kPa 

412 

88 

393 

1,143-1,283 

ALL BITS 

- Total.. . 1 15-504 ( 50-1,652 1 494 1 1,622 1 15,775 1 31.9 1 9.7 12,750-6,2001 400-900 1

NAp Not applicable. 

391-434 

, 434-504 

391-504 

100 

993 

5,065 

1,693 

4,095 

312-391 

43 

1,283-1,423 

1,423-1,652 

1,283-1,652 

838 

11,484 

260 

40.5 

62.7 

34.1 

1,023-1,283 

140 

27.9 

37.9 

79 1,961 

58 

70 

112 

12.3 

19.2 

10.4 

1,354 

140 

229 

369 

8.4 

11.6 

24.8 

1,644 

479 

2,123 

2,750-4,800 

2,750-3,800 

3,450-4,800 

31.5 

4,100-6,200 

2,750-6,200 

7.5 

400-700 

400-550 

500-700 

9.7 

28.3 

6.8 

19.0 

600-900 

400-900 

4,500-6,200 

4,500-4,800 

3,450-4,500 

3,450-4,800 

11.7 

2.1 

5.8 

4,500-4,800 

650-700 

500-650 

500-700 

650-700 

650-900 
yp, () 

It should be noted that the use of 

flow rates higher than for which the tool 

was designed results in a corresponding 

increase in the stresses on the bearings, 

universal joints, and shafts. This means 

that failure and replacement of these 

components will happen nore often. It 

was felt that during pilot hole drilling 

the timesaving fron increased penetration made these costs acceptable. However, during horizontal drilling in coal, 

where a pipe trip often took as long as 

12 hours, and where the tool could drill 

nearly as fast (0.15-0.6 m/min or 0.5- 

2.0 ft/min) at 5.5 m3/h (24 gallmin), as 

at 11 m3/h (48 gallmin), this loss of 

tool life was not considered acceptable. 

It can be seen from table 2 that the 

Strata-Pax bits generally drilled more 

effectively in soft formations (shales) 

than diamond bits. The diamond bits 

(fig. 9) drilled better in the hard formations such as limestones and sandstone. 

Overall, the efficiency of the two bit 

types was comparable and the choice of 

one over the other would basically be a 

matter of cost. Table 3 shows the distances drilled and net cost for each of 

the 76-m (3-in) diameter hits used in 

both pilot and horizontal drilling. The 

average per meter cost of a Strata-Pax 

bit in pilot hole drilling was roughly 

$6.50 ($1.98/ft). The diamond bit cost 

per meter cannot be determined exactly 

but it would he between $2.00 and $6.50 

($0.61-$1.98/ft). This indicates that 

diamond bits were more econonical (similar results can be seen when comparing 

the bits in horizontal drilling in 

coal). 
TABLE 2. - Selected penetration rates versus formation types 

TABLE 3. - Bit costs--pilot and horizontal holes 

date 

STRATA-PAX. TYPE 128181. SN-8S46823 

a--- - - -- Drilling 

-- rate - 

min/m min/f t 

112.9 34.4 

23.6 7.2 

26.2 8.0 

17.1 5.2 

24.3 7.4 

17.7 5.4 

35.4 10.8 

24.6 7.5 

18.7 5.7 

3.3 1.0 

--- - 

Bit type 

. 

Strata-Pax 1 

Do.. . . . . . . Do.. . . . . . . Do........ 

Diamond.. . . . Do........ 

Do.. . . . . . . Do........ 

Strata-Pax 2 

- Do........ 

- -- Distance 

on bit 

4- 

November 19781 1,929.501 one 1 1,929.501 - '15- 312 1 ---- '50- 1 , 023r-197T--97316.56T-i.98 -- 

STRATA-PAX, TYPE 128181, SN-8S55183 

--- - - -- -- - - Estimated pump 

-- pressures ---- k Pa ~b/in~~ 

3,406-" 500 

4,100-4,800 600-700 

4,100-4,800 600-700 

4,100-4,800 600-700 

6,200 900 

6,200 900 

4,500-4,800 650-700 

4,500-4,800 650-700 

4,500-4,800 650-700 

3,400-4,500 500-650 

-- - -- - - -- --- - - - -- Measured depth 

-m 

27.4 

69.5 

75.3 

199.3 

5.2 

33.5 

42.7 

49.4 

46.3 

91.1 

- - - - --- - - - -- -- -- 

- -- -- --- 

Format ion 

---.-ACement. 

Shale. 

Limestone. 

Sandstone. 

Shale. 

Limestone. 

Shale. 

Limestone. 

Shale. 

Coal. - 

ra 

. - -- - - -- 36.6- 39.6 

78.6- 80.5 

84.4- 86.3 

208.5-210.3 

317.0-320.0 

345.3-347.5 

354.5-355.7 

361.2-364.2 

437.4-439.5 

482.2-485.2 

ft 

90 

228 

247 

654 

17 

110 

140 

162 

152 

299 

-- f t 

---- 

120- 130 

258- 264 

277- 283 

684- 690 

1,040-1,050 

1,133-1,140 

1,163-1,167 

1,185-1,195 

1,435-1,442 

1,582-1,592 

l1,283-1,652 

'1,597-1,872 

'2,392-3,362 

1,847.25 

----. 

DIAMOND 3-INCH SHALLOW CONE, TYPE 147496, SN-8S54001 

'391- 504 

"87- 571 

"29-1,025 

------- I January 1979. 1,376.98 

- ------a 

'312- 391 

2571- 802 

'674- 729 

'1,023-1,283 

'1,872-2,632 

'2,212-2,392 

644.06 

=OND INCH DEEP CONETYP 1474g4, SN-~S~~OOO-- 

732.92 

931.08 (4) 

---- 

495.92 

- DIAMOND 3-INCH SHALLOWCONE TYPE 20-186-037s ~~-9~52E3 

August 1979.. 1,737.45 978.37 757.08 3827- 833 32,712-2,732 1,992 

7583- 740 71,912-2,428 

7717- 752 72,352-2,465 

8501- 562 81,642-1,842 

- ----- - - --- - --- -- ---- - 8552- 702 81,812-2,302 

--- 

------ IDIAMOND 3-INCH sGKL~W-CONETYPE 20-186-0373, SN-9~49747 

June 1979.. .7--=0.63 '0 1,770.63 3549- 702 31,802-2,302 233 

--- -- --- -.---- 3610- 691 32,002-2,266 -- 

--- .--------- ALL BITS 

Total or 

Average. 

3498- 549 

5498-1 ,399 

6833-1,464 

31,632-1,802 

51,632-4,588 

'2,732-4,802 

NAp Not applicable. 

lpilot hole. 

2~orizontal hole, H1. 

3~orizontal hole, HZ. 

4~ost included with following bit. 

5~orizontal hole, H3. 

'1nsuf ficient records to determine which of these two bits drilled these intervals. 

7~orizontal hole, H4. 

8~orizontal hole, H5. 

 it lost in hole. 

10,086.81 2,553.51 7,553,30 
Drilling Summary 

The directional pilot hole was begun 

on November 9, 1978, at a depth of 15 m 

(50 ft) and was completed on December 19, 1975, at a total measured depth 

of 504 m (1,652 ft). Drilling was done 

24 hours per day on weekdays and the job 

was shut down on all but one weekend. 

The pilot hole drilling operation was 

completed in 965 hours (or 40 calendar 

days). Of this time 240 hours were off 

days, 262.5 hours were spent drilling, 

86 hours surveying, 38 hours in normal 

maintenance, 43 hours tripping pipe to 

change bent housings, and 295.5 hours 

were downtime (appendix A). The actual 

time required to drill the pilot hole was 

the sum of all of these except the downtime and theoff days, or a totalof 

429.5 hours (about 18 days). The average 

drilling rate was 28 m/d (92 ftld). 

Problems were encountered in the 

pilot drilling with the mud pumps, the 

rig, the Dyna-Drill, the drill pipe, and 

with lost circulation. The mechanical 

problems, especially those of the mud 

pumps, were primarily those normally to 

be expected in breaking in new equipment 

and were minor (appendix A). However, 

about 87 hours were lost both directly 

and indirectly to lost circulation. 

Although this represents only 9% of the 

total time spent in pilot hole drilling 

it was an indication of greater lostcirculation difficulties ahead in the 

reaming operation. Also, not only was 

lost circulation expensive in project 

hours but the costs for water and mud 

were also extremely high ($31,000 for 

pilot hole drilling). The problem continued during the reaming operation. 

The drilling fluid originally used 

was a Dextrid and XC Polymer mud 

(fig. 10) designed to decrease fluid 

loss, to be low in solids, and to act as 

a gel to aid in cuttings removal. This 

type of mud had proven to be very effective during the drilling of the Mather 

directional hole. However, the lostcirculation zones in EM-19 proved to be 

too much for the mud's sealing capabilities. In order to slow down fluid loss, 

such additives as cottonseed hulls, cellophane flakes, and ground walnut shells 

were put in the mud. All were lost in 

the hole. The pilot hole drilling was 

completed using essentially pure water 

with little or no circulation. 

Attempts were also made to treat the 

lost-circulation problem with cement and 

later with "gunk squeezes." Two cement 

plugs were set in the first 34 m (110 ft) 

of the hole, but they were difficult for 

the Dyna-Drill to drill through and were 

not effective, so their further use was 

abandoned. A gunk squeeze consists of 

punping or pouring a slurry of powdered 

bentonite clay, diesel fuel, and (sometimes) cottonseed hulls into the hole. 

When the slurry comes in contact with 

water (presumably in the fractures of the 

formation taking fluid), the bentonite 

swells and the slurry expands to become a 

highly viscous gel that is difficult to 

move. The gunk squeezes were continued 

regularly through the pilot hole drilling 

operation and in the reaming operation. 

They helped to reduce fluid losses, but 

did not completely shut off the problem 

zones. 

After the pilot hole was completed, 

a string of used BCQ wireline rod (similar to BQ rod) was run in the hole, to be 

used as a guide string for overreaming 

bits that opened the hole to 222 mm (8- 

314-in) in diameter. 

A gamma-ray log of the hole was also 

run through the guide string before the 

reaming operation was begun. This log 

was interpretated to show that the hole 

had entered the top of the Pittsburgh 

coalbed. When horizontal drilling was 

begun it was found that the hole was 

actually 0.5 to 1 m (2 to 3 ft) above the 

coalbed. 

'l~hird work cited in footnote 3. 
FIGURE 10. 

 Mixing Dextrid-Polymer mud for pilot hole drilling. Sacks of Dextrid at left, FWI 

pumps at center, and Gardner-Denver pump at right. 

Reaming 

Reaming was begun on January 8, 

1979. Operations were carried out on a 

24-h basis with weekend shutdowns. A 

string of 25.4-mn (1-in) pipe was first 

run inside the BCQ rod, installed earlier, to stiffen it. The reaming was 

done using a rented string of 89-mm (3- 

112-in) diameter drill pipe with I. F. 

connections. Both Strata-Pax and diamond 

drill bits were used (fig. 11). The 

first reaming bits (two of an eventual 

five) used were 222-nm 0.d. by 63-mm i.d. 

(8-314 by 2-112 in). 

operation. The additives included cottonseed hulls, cellophane flakes, and 

ground walnut shells. The Strata-Pax bit 

used to begin the reaming was designed to 

allow the circulation of large pieces 

of solid lost-circulation material 

(fig. 11). In spite of the precautions 

taken to prevent lost circulation, all of 

the 30 m3/h (130 gallmin) mud volume 

being pumped was being lost by the time 

the hole had been overreamed to 12 m 

(40 ft) MD. The hole was then drilled 

blind (without circulation) for several 

days until reaming reached a measured 

depth of 62 m (205 ft). 

Lost Circulation In an effort to permanently stop the 

lost-circulation problem encountered near 

Because of the problem of lost cir- the surface, the upper 35 m (115 ft) MD 

culation experienced in the pilot hole of the hole were reamed to a 254-mm 

drilling, a high viscosity bentonite (10-in) diameter and an attempt was made 

(gel) nud with lost-circulation additives to run 245-m (9-518-in) diameter casing 

was used at the start of the overreaming to 34 m (110 ft) MD to shut off what was 
FIGURE 11. - Reaming bits. Strata-Pax at left shows matrix damage after drilling 83 rn (273 ft). 

believed to be the main problem zone at 

27 to 31 m (90-100 ft) MD. The casing 

was welded to eliminate the larger diameter of the casing collars. The pipe 

hung up in the hole at 27 m (88 ft) MD 

and a fishing operation was required to 

remove it from the hole. At the same 

time as the fishing operation, the turbocharger of the rig malfunctioned and it 

had to be replaced. It was not until 

January 30, 1979, that the rig was repaired and the casing removed from the 

hole, Once this was accomplished the 

hole was again reamed, this time to 

279m (11 in) in diameter to a depth of 

36.6 n (120 ft) and 245-mm (9-518-in) 

diameter casing, with collars, was set at 

a depth of 34 m (111 ft). 

This casing did not solve the lost 

circulation problem and blind drilling 

was continued until a measured depth of 

101 m (331 ft) MD was reached. At that 

time the valves of the Gardner-Denver 

5x10 FCFXD duplex pump required replacement and since new valves were not immediately available a switch was made to 

air and foam drilling. In addition, at 

83 m (273 ft) MD the matrix material of 

the first bit (the Strata-Pax bit) began 

to come apart and it was replaced by a 

diamond bit (fig, 11 shows the Strata-Pax 

bit after it began to come apart and the 

diamond bit just before it went in the 

hole). Overreaning with foam was continued until a measured depth of 147.5 m 

(484 ft) MD was reached, although the use 

of foam did not adequately lubricate or 

cool the bits. At 147.5 m (484 ft) MD, 

when the new pump valves had been 

received and installed, another attempt 

was made to drill with mud. This time a 
salt-saturated mud was used to prevent 

the pits from freezing. Again circulation was immediately lost. The use of 

gunk squeezes, which had reduced fluid 

losses during pilot hole drilling, was 

reinstituted. These treatments sometimes 

helped for short periods of time, a few 

hours or as much as a day, but often were 

completely ineffective. 

Fishing Operat ions 

The use of gunk squeezes eventually 

led to BCQ rod being stuck inside the 

drill pipe. Attempts to free the BCQ 

from the drill pipe caused both the 

25.4-mm (1-in) pipe and the BCQ rod to 

back off (unscrew) in the hole and a 

number of fishing trips over a 2-day 

period were required to obtain a continuous string of 25.4-mm (1-in) pipe to the 

surface. The BCQ had backed off at about 

90 m (300 ft), but no attempt was made to 

screw into the BCQ rod, since the 25.4-mm 

(1-in) pipe was continuous to the 

On February 21, 1979, a new StrataPax bit (fig. 12) was received and was 

immediately run in the hole to replace 

the diamond bit that had been worn out. 

The new bit began reaming at a measured 

depth of 186.5 n (612 ft). It had reamed 

only 2.5 m (8 ft) when the bit crown 

separated from its shank. Because of the 

BCQ rod and 25.4-mm (1-in) pipe in the 

hole, and the fear that the pilot hole 

would be lost if that pipe were removed, 

an attempt was made to grind up the bit 

crown with a milling tool. However, before the mill could reach the bit crown 

it cut the 25.4-mm (1-in) pipe in two and 

left a number of pieces of pipe scattered 

throughout the reamed portion of the 

hole. 

Attempts to fish the 25.4-mm (1-in) 

pipe were then begun and continued without success until a television camera 

(fig. 13) was brought in and run in the 

hole on March 13, 1979. Using the camera 

it was possible to find the main string 

of pipe and determine its condition. On 

the second fishing attempt after sighting 

the top of the main string of the 25.4-mm 

(1-in) pipe, the overshot tool latched 

onto the pipe and both the main string of 

25.4-mm (1-in) pipe and all of the BCQ 

rod in the hole were brought out. Four 

more days were required to fish shorter 

sections of 25.4-mm (1-in) pipe from the 

hole using alternating overshot and camera runs. Finally, when most of the 

remaining pipe was below the water level 

in the hole (the camera could not give a 

usable picture in water because of the 

suspended solids), a switch was made to 

grinding the pipe with a mill and fishing 

the small pieces (fig. 14) with a magnet. 

The last of the debris was removed from 

the hole on March 8, 1979. A spear with 

spring-loaded latches (fig. 15) was 

used to retrieve the bit crown on 

March 30, 1979. 

This fishing operation cost 26 working days (41 calendar days) and approximately $93,000. The direct and indirect 

labor costs totaled $49,800 and the costs 

for fishing tools were $22,600. Had 

there been no BCQ or 25.4-mm (1-in) pipe 

in the hole the crown could have been 

fished directly using the spear, at 

greatly reduced cost. 

Reaming With a Stinger Assembly 

Reaming operations were finally 

resumed on April 4, 1979, using a stinger 

(figs. 12 and 16) to guide the bit, 

instead of the pipe string that had 

been removed while fishing the bit crown. 

The use of a stinger soon proved to be as 

effective as, and far safer than, the use 

of a guide string. No attempt was made 

to run the guide string again and no 

problems were encountered in the use of 

the stingers . 

Drilling Summary 

The reaming operation was completed 

on May 9, 1979. The operation took 

121 days, of which 40 were off days and 

26 were spent in fishing for the bit 

crown. The average drilling rate was 

approximately 1 m/h (3.4 ft/h). However, 

the overall drilling rate when fishing, 

downtime, and off days are included, 

drops to less than 0.2 m/h (0.6 ft/h). 

The average bit cost per meter was $46.90 

($14.90/ft) (table 4). 
TABLE 4. - Bit costs--reaming 

Bit l 

Strata-Pax : 

Type 11660, 

SN-8~55615~. . . . . . . 

PT 11685, 

SN-9~42322 3....... 

SN-9~41252~. . . . . . . . Diamond : 

Type 147568 2 SN-8S56468 ....... 

Type 20-358-024-S, 

SN-9~45758~. . . . . . . 

Type 20-358-024S, 

SN-9~46901 3.. . . . . . 

Total or average 

NAp Not applicable. 

'All bits were acquired in January 1979. 

2222.25 mm by 63.5 rnm (8-3/4 by 2-1/2-in). 

3219 mm by 63.5 mm (8-5/8 by 2-1/2-in). 

'probably damaged by steel in the hole after the fishing job. 

'NO charge because bit came apart in the hole. 

Initial 

cost, l 

dollars 

4,215.82 

4,750.00 

SO 

9,165.36 

9,214.06 

9,343.29 

36,688.53 

Salvage 

value, 

dollars 

None 

None 

None 

3,368.71 

5,073.26 

5,073.26 

13,515.23 

Net cost, 

dollars 

4,215.82 

4,750.00 

0 

5,796.65 

4,140.80 

4,270.03 

23,173.30 

Depths 

m 

0- 83 

189-257 

187-189 

83-187 

257-369 

369-494 

NAP 

drilled - f t 

0- 273 

620- 842 

612- 620 

273- 612 

842-1,209 

1,209-1,620 

NAP 

Total dept

drilled 

m 

83 

'68 

2.4 

103 

112 

125 

494 

f t 

2

42

3

3

4

1,6
FIGURE 12. - Flat-faced Strata-Pax reamer and stinger. Stinger diameter is 63 rnm 

(2-1/2 in). 
FIGURE 14. - Debris fished from EM-19. Long pieces were picked up by overshof and small 

pieces by magnet. 
FIGURE 15. - Bit-crown fishing spear. Large ring at the to

is a centralizer. 
Casing and Cementing 

The hole was cased on May 10, 1979, 

using 486 m (1,595 ft) of 140-m (5- 

112-in) o.d., K-55 grade, range 2, LT&C 

casing. The casing ran freely to a depth 

of 442 m (1,450 ft). Below that point it 

was necessary to fill the casing with 

water to reduce its buoyancy, and to use 

the rig to push the casing to the desired 

depth. The next-to-last joint of casing 

required a down pressure of 57,800 11 

(13,000 lb) and the last joint required a 

down pressure of 8,900 N (2,000 lb). 

Fifteen centralizers were also run in the 

hole, most of them on the bottom 91 m 

(300 ft), to insure a uniform cement 

sheath around the pipe in order to provide a good seal. 

The cementing operation was completed on May 11, 1979. A total of 

9.6 m3 (340 sacks) of Pozzolan cement 

were used, with gilsonite added to 

decrease the cement density and help prevent the lost-circulation zones from taking all of the cement. Good cement 

returns were obtained at the surface, 

indicating that the cementing operation 

was successful. On May 16 the bottom 

hole plug was drilled out, using a string 

of 60-mm (2-318-in) drill pipe and a rock 

bit, in preparation for the horizontal 

drilling. 

Horizontal Drilling 

Horizontal drilling with the DynaDrill was begun on May 17, 1979. It was 

planned initially to drill just enough 

hole t o d r i l l slightly past the vertical 

dewatering hole EM-20 (fig. 17). Drilling was then to be suspended and a 

hydraulic stimulation treatment done on 

EM-20. The horizontal hole was drilled 

to 528 m (1,732 ft) MD on May 23, slightly past EM-20. The dewatering hole was 

stimulated on May 25 with a 70.5-m3 

(21,000-gal) foam treatment containing 

11,800 kg (26,000 lb) of 20140-mesh sand 

propping agent. This procedure was 

designed to provide a path for increased 

flow of water to the vertical dewatering hole EM-20 by providing a direct 

high-permeability connection between the 

horizontal holes and EM-20. 

Cuttings from the pilot hole drilled 

in December 1975 and interpretation of 

the gamma-ray log run at the same time 

indicated that the directional hole had 

entered the top of the Pittsburgh coalbed 

at about 486 m (1,595 ft) MD. This point 

had therefore been chosen for the bottom 

of casing. The initial horizontal drilling indicated that the interpretation had 

been incorrect. It was found necessary 

to drop vertically through approximately 

0.6 n (2 ft) of roof rock to enter the 

main bench of the coalbed. Reevaluation 

of the gamma-ray log in light of the 

additional drilling information indicated 

that the pilot hole probably had been 

drilled through the rider coal above the 

Pittsburgh, into the roof shale directly 

above the Pittsburgh coalbed and then, 

instead of entering the Pittsburgh coal 

the hole either reentered the roof coal 

or terminated in the shale. Because of 

the similarity in hardness and color of 

the shale and coal, the boundary of the 

roof coal and shale was not even noted at 

the time by the driller. Even after completion of all of the drilling and close 

scrutiny of the original gamma-ray log it 

is difficult to make an interpretation of 

the exact sequence of rock types 

drilled. 

The error proved to be a major problem for two reasons. First, the vertical 

dewatering hole and the directional hole 

had been placed so that fractures from 

the stimulation treatment of the coalbed 

done in EM-20 would cross the path of the 

horizontal holes just beyond the bottom 

of casing. Since the horizontal hole was 

probably in shale near the anticipated 

point of intercept with the stimulation 

fracture (fig. 17), direct communication 

may not have been achieved. Figure 17 

indicates that the fracture intercepted 

horizontal hole H1. However, the uncertainty in the position of EM-19 with respect to EM-20 is sufficient that the 

fracture could easily have crossed the 

hole where the hole is in rock. Indeed, 

no sand was ever seen in the cuttings 
from the directional hole. Secondly, 

this meant that the initial portion of 

each horizontal hole was in rock which 

had a tendency to cave or slough, resulting in plugging of the holes. The best 

method of insuring that the casing 

reaches the target coalbed in future 

directional holes would be to continue 

the pilot hole after reaching the horizontal, and to then drill steeply downward until the bottom of the coalbed is 

reached. This portion of the hole would 

confirm the well position and would then 

be abandoned during the reaming and casing operations. 

Horizontal Hole HI 

Continuous drilling of the first 

horizontal leg H1 (fig. 18) was begun on 

May 29, 1979. Clear water was used as 

the drilling fluid to eliminate any risk 

of mud additives plugging the coalbed 

fracture system. However, the use of 

clear water led to three problems. The 

first and most important was that the low 

viscosity of water made removal of drill 

cuttings from the hole more difficult. 

The problem was made more acute by 

the low flow rates required by the 

ILL 

W 

> 

W 

3 

LL SECTION VIEW t- (Vertical exaggeration, X 4) 

31 0 

2 70 280 290 300 310 320 330 340 350 360 

HORIZONTAL DISTANCE FROM SURFACE LOCATION OF EM-19 ALONG N 41" W, rn 

FIGURE 17. - Plan and section views of geometry of EM-19 near the bottom of casing. EM-20 

location also shown. 
creased from 5.5 to 9.0 m.?/h (24- 

40 gal/min) and eventually to as high as 

13.6 m3/h (60 gal/min). This increase in 

flow rate eventually led to problems with 

Dyna-Drill tool life. 

A second problem encountered when 

using clear water was fluid loss. This 

problem essentially could not be solved 

without the risk of damaging the coalbed's natural fracture permeability and 

decreasing future methane gas flow rates. 

Fluid losses as high as 57 m3/d 

(15,000 gal/d) were experienced before H1 

tional control engineer was still learning how to control the drilling assembly, 

and because it was difficult to predict 

the dip of the coalbed, large sections of 

hole H1 were drilled in rock (fig. 18 and 

table 5). One sidetrack was attempted on 

hole H1 because a large section was 

drilled completely in rock between 

685.2 and 801.6 m (2,248-2,630 ft) MD. 

The hole was successfully sidetracked in 

coal at 674.2 m (2,212 ft) MD and was 

drilled to 976.6 m (3,204 ft) MD with 

only two short sections totaling 8.5 m 

(28 ft) in rock. 
TABLE 5. - Horizontal distances drilled 

NOTE.--Total all drilling, 3,311 m (10,882 ft). 

The drilling assembly used to drill 

H1, and later holes H2 and H3, was the 

same one used to drill the pilot hole 

(fig. 7). In horizontal drilling, however, the emphasis is on maintaining hole 

angle against the force of gravity, without building angle. One attempt was made 

to use the 0.0087-rad (30-min) bent housing to maintain angle, but it was found 

inadequate during the occasional periods 

when rapid building of angle was 

required. The 0.013-rad (45-nin) bent 

housing was then tried and became the 

standard assembly for drilling the horizontal holes. The 0.013-rad (45-nin) 

housing could actually build angle at a 

greater rate than usually required. 

Since its additional build capacity could 

not be "turned off," a technique was 

developed by the directional drilling 

engineer to render this capacity relatively harmless when not needed and 

available when required without making 

pipe trips to change housings. This was 

done by rotating the "tool face," the 

plane of the bend, to some angle, typically about 0.79 rad (45") either right 

or left of vertical. This rotation would 

be held either right or left as required 

for about 100 m (330 ft) and then the 

tool face would be turned the other way. 

This resulted in a smooth, sinuous hole 

path, as seen in plan view (fig. 18). 

The additional curvature did not increase 

-- 

Hole 

Hl......... 

H2......... 

H3......... 

H4 ......... H5......... 

-- Total... 

Hole H1 was initially surveyed after 

each 3.3-12 (10- ft) pipe joint was 

drilled. As the directional drilling 

engineer gained experience and information on the coalbed, the interval was 

increased to two joints, except at critical points. Because of the uncertainty 

in control techniques and the lack of 

information on the coalbed structure, 

about 38% of the total of 666 m 

(2,185 ft) of horizontal hole H1 was 

drilled in rock, 

NAp Not applicable. 

Hole in rock, 

including 

sidetracks 

A total of 15 full and 2 partial 

pipe trips were made while drilling 

H1, 10 of which were required to 

retrieve the survey tool after it had 

hung up in the drill pipe and caused the 

wireline to break. This was a serious 

problem while H1 was being drilled, but 

better equipment eventually solved the 

difficulty. Three trips were also made 

because of Dyna-Drill failures, and one 

trip each due to a plugged bit, a change 

of bent housings, a parted BQ rod, and a 

weekend shutdown. 

m 

253.0 

180.7 

73.5 

95.1 

29.9 

632.2 

1 was terminated prematurely 

on July 13, 1979, at 1,024.7 m (3,362 ft) 

MD when it was found to be impossible to 

reenter the hole after a pipe trip. The 

hole had reached a total horizontal 

distance of 538.6 m (1,767 ft) (table 5) 

beyond the end of casing and was drilled 

-- 

Total depth 

from surface 

f t 

830 

593 

241 

312 

98 

2,074 

pipe friction much because it was done in in 26 working days, an average of 20.4 m 

a smooth and gradual manner. The hole (67 ft) per day, Before the leg was 

projection was followed by having the terminated it had become apparent that 

m 

1,024.7 

1,463.4 

1,398.4 

751.3 

701.6 

NAp 

curves repeatedly cross left and right of many improvernents would be required to 

the desired path. obtain acceptable daily drilling rates. 

f t 

.-- 

3,362 

4,802 

4,588 

2,465 

2,302 

NAP 

Horizontal length, 

casing to total 

depth 

--- ' Hole in coal, 

including 

sidetracks 

m 

538.6 

977.5 

912.3 

265.2 

215.5 

2,909.0 

m 

413.0 

1,018.6 

915.0 

157.6 

180.4 

2,684.7 

f t 

1,767 

3,207 

2,993 

870 

707 

g;544 

ft 

1,355 

3,342 

3,002 

517 

592 

8,808 
Horizontal Hole H2 

Leg HZ was begun on July 16, 1979, 

and about one-half of its total length 

was completed before the necessary 

changes in drilling technique could be 

developed and put to use. The first 

action taken was a meeting with DynaDrill engineers to discuss the problems 

of tool life and reliability. Two 

changes were made after this meeting. 

The flow rates through the Dyna-Drill 

were reduced in an attempt to decrease 

stresses on the tools, increase tool 

life, and reduce the number of pipe trips 

required for tool repair. (At measured 

depths of 1,000 m (3,300 ft) a pipe trip 

could take as long as 16 hours.) The 

second change was made to offset the 

effects of lower flow rates on cuttings 

removal, by the addition of Con-Det, a 

concentrated detergent, to the drilling 

fluid. The Con-Det acted to help remove 

cuttings, but presumably did not plug off 

the coalbed fracture system. Evidence 

that this was the case came from several 

of the vertical monitoring holes where, 

after long periods of stability the surface pres&ures measured in the monitor 

holes increased shortly after use of the 

Con-Det was begun. This was probably due 

to an increase in permeability in the 

horizontal holes themselves when the fine 

cuttings were removed. Eventually an 

experimental partial bypass valve 

(fig. 7) just above the Dyna-Drill tool 

was also used which allowed high flow 

rates in the hole, but allowed only flows 

of 5.5 m3/h (24 gal/min) through the 

tool. The rest of the flow bypassed the 

Eyna-Drill by way of the valve. 

The problems associated with drilling in rock (primarily hole caving, but 

also sticking of drill pipe) were eliminated when it was discovered that it was 

easier to back up and sidetrack immediately after leaving the coal (fig. 19B) 

than to try to gradually guide the well 

path back into the coal (fig. 19A). 

Eventually sidetracks could be accomplished in as little as 3 hours with no 

problems in reentering the proper hole. 

The acceptance of more sidetracks 

also made staying in the coalbed less 

critical. This allowed an increase 

in drilling rates and an increase in 

FIGURE 19. - Two methods of fol lowing the coalbed. Method B is recommended. 
surveying intervals from every one or two 

joints of pipe to every two to four 

joints. Since it took about 1 hour for 

an average survey and only 20 to 40 minutes to drill two joints (6.6 n or 20 ft) 

the time saving was significant, an 

increase of about 40% in the drilling 

rate. 

Leg H2 (fig. 18 and table 5) was 

completed on August 31, 1979, at a total 

measured depth of 1,463.4 m (4,802 ft). 

Of the total horizontal distance drilled, 

1,199.3m (3,935 ft), only 15% was in 

rock, a great improvement over the 

results of H1. The maximum horizontal 

distance reached from the bottom of casingwas 977.5m (3,207 ft) which made it 

the longest horizontal hole drilled in 

EM-19. H2 was drilled with a total of 

five sidetracks, which took up 221.8 m 

(728 ft) of the total distance drilled. 

One of these sidetracks was required when 

a broken drive shaft in the Dyna-Drill 

caused a bit to be left in the hole. 

When fishing failed to remove the bit 

this hole had to be abandoned and 

sidetracked. 

A total of 16 pipe trips were made 

in H2, 11 because of Dyna-Drill failures, 

and one each caused by a survey purnpdown 

tool failure, a drill rod parting, a bit 

change, a bent housing change, and the 

completion of the hole. The average 

daily footage was 27.1 m (89 ft) indicating that the improvements in drilling 

methods, although introduced about half 

way through the drilling of H2, had begun 

to have a positive effect. 

Horizontal Hole H3 

All of the successful techniques 

developed while drilling H1 and H2 were 

used in drilling leg H3, except the use 

of the bypass valve which had been sent 

in for repairs when H3 was started. H3 

was begun on September 4, 1979. On 

September 21, 1979, the Dyna-Drill was 

finally pulled out of the hole after 

drilling all of H3 in a single run of 

226 drilling hours. The hole had been 

drilled to a measured depth of 1,398.4 n 

(4,588 ft), a horizontal distance of 

918.3 m (2,993 ft) from the end of casing 

(fig. 18 and table 5). The average distance drilled per working day (14 days) 

was over 64.9 m (213 ft). The hole was 

sidetracked eight times for an average of 

114 m (374 ft) between sidetracks. Only 

about 7.5% of the total length of hole 

drilled was in rock and beyond a measured 

depth of 522 m (1,712 ft) the hole was 

continually in coal, except for short 

"dead ends" in rock which were bypassed 

each time the hole was sidetracked. Leg 

H3 was also terminated prematurely 

because it could not be reentered due to 

apparent sloughing of the shale section 

at the bottom of casing. If the hole 

could have been reentered, there is every 

reason to believe that it could have 

been extended a substantially greater 

distance. 

Horizontal Holes H4 and H5 

After September 21, 1979, several 

unsuccessful attempts were made to reenter the horizontal holes and as part of 

these attempts two additional holes, H4 

and H5, were drilled. H4 essentially 

followed the path of H1 and H5 was 

drilled between H1 and H3. 

Reaming Horizontal Sump 

The final drilling operation performed on the directional hole was the 

reaming of a 45-n (147-ft) long horizontal sump, 216 mm (8-112-in) in diameter from the bottom of casing to a measured depth of 531 m (1,742 ft). The 

exact path of this sump was not surveyed, 

but it is assumed to have followed the 

path of H2, since it entered the coal at 

522 m (1,712 ft) MD, the same depth that 

H2 entered the coal. This underreaming 

took approximately 2 days, most of which 

was spent in running and pulling the 

121-m (4-314-in) diameter tricone bit 

and the 216-nn (8-112-in) diameter casing 

underreamer (fig. 20) used to open the 

hole. The operation was completed on 

October 9, 1979. The sump was drilled 

partly as a gathering area for water and 

partly to help keep a path open through 

the roof shales which had already shown 

themselves to be major problems. 
FIGURE 20. - Casing underreamer. Open diameter, 216-mm (8-1/2-in); closed diameter, 

121-mm (4-3/4-in). 

Com~letion Work and Initial 

Production Rates 

Work was begun on October 9, 1979, 

to equip the vertical dewatering hole, 

EM-20, to dewater the coalbed, and to 

equip it and the directional hole for gas 

production (fig. 21). EM-20 (fig. 22) 

was put on water production using a downhole plunger pump on November 15. Water 

production began at the pump's capacity 

of 20.3 m3/d (128 bbl/d) but declined 

rapidly. The initial gas flows ranged up 

to 34 n3/d (1,200 ft3/d) (fig. 23), but 

no increase in gas production was seen 

as the water production dropped. At the 

same time pressures in the coalbed, read 

from the vertical monitor holes, initially dropped rapidly and then leveled off. 

It was believed that either barrier to 

water flow between EM-20 and the directional hole, EM-19, caused by caving of 

the horizontal holes where they had been 

drilled in roof rock at the bottom of 
FIGURE 21. - EM-19 surface installation. Wellhead and pump control panel at left. 

casing or the plugging of the induced 

fractures from the stimulation treatment 

were directly responsible. During the 

period December 1979 through February 

1980, several attempts were made to 

increase water production by flushing out 

both EM-20 and EM-19 with water in the 

hope of cleaning out material that might 

be blocking the fracture system and the 

holes. Attempts were also made to open 

up the fracture originally created in EM20 by punping in water at pressures well 

above those required to induce the original fracture. The indications are that 

these procedures did not accomplish the 

desired results and nay have caused harm 

by accelerating the caving of shales at 

the botton of casing in EM-19. 

Tests conducted in EM-19 in January 

1980, using compressed air to remove 

water fron the hole, showed that water 

production rates as high as 31 to 48 rn3/d 

(220-300 bbl/d) could be sustained for a 

week or longer. During these tests, gas 

flows of up to 2,500 m3/d (90,000 ft3/d) 

were seen for brief periods after the air 

compressor was shut off, and shortly 

before the increasing pressure of the 

water column in the hole prevented further gas flow. 

In February 1980, water level measurements were made in EM-19 which indicated a botton hole pressure of 1,280 kPa 

(186 ~b/in~~), whileat the same time the 

pressure in EM-20 was atmospheric. Since 
EM-20 pump 

KEY 

~~~~ EM-20 water flow reading 

- 200 

30 - d?wn I day 

500 

g 400 

E EM-19 gas flow read~ng 

j 300 

9 

200 V) 

a 

100 

0 100 200 

TIME, days 

FIGURE 23. - Production data from EM-19 and EM-20. 
FIGURE 24. - Crew running the submersible pump into EM-19. Note centrarizers for motor at right. 
FIGURE 25. - Shale and coal blown out of EM-19, January 1980. Pen cap 57 mm (2.25 in) long. 

Note large cement piece. 
In May 1980, work was begun to further caving of the roof shales and to 

design equipment to redrill the hole from create a permanent path for water and gas 

the bottom of casing in EM-19, through movement from the horizontal holes H1, 

the roof shale and well into the Pitts- H2, and H3 into the casing of the direcburgh coalbed. A plastic liner casing tional hole. 

will be installed in this hole to control 

PROJECT COSTS 

Detailed Cost Analysis 

Table 6 shows the costs for the 

directional hole, EM-19, broken down by 

major expenditure items. The total costs 

column shows the actual total of all of 

the invoices received from the contractor. The project startup column gives 

the costs of maintaining key personnel 

from September 1977 to August 1978, while 

the cooperating coal company searched for 

an alternate drilling site. The original 

site became unavailable at about the same 

time as the drilling contract was signed. 

The fishing costs column gives the costs 

of the February-March 1979 bit-crown 

fishing job during the reaming operation. 

The end-of-project column gives the 

breakdown of the costs at the end of 

the project between November 1979 and 

May 1980 to put the system on production 

and to maintain a capability to perform 

service and remedial work. In the last 

column, the total EM-19 costs, minus the 

nondrilling and major fishing costs have 

been computed. 

The net costs in table 6 give an 

estimate for the cost of the directional 

hole at 1979 prices ($1,169,530.58) 

assuming that no unanticipated expenditures such as those identified had been 

encountered. The cost of the vertical 

dewatering hole, the monitoring holes, 

and the corehole are also not included. 

Nor are costs for drill rig and mud pump 

rental since these were Government owned. 

Also, the costs of site preparation are 

not included because they were paid by 

the Emerald Mines Corp. 
TABLE 6. - Directional hole (EM-19) drilling costs 

(1979 dollars) 

---- -- --.----------------- ---------- --------- ------- -------- ] :a::: I [ E::" I ::%it:; 1 Net COS~ 

------ - ------------- ----- (reaming) ------ ------- DIRECT 

Labor: 

Nonsupervisory................ 

- 

Geolograph.................... 

Directional control equipnent. 

Directional drilling engineer. 

Dyna-Drill....... ............. Bits and subs................. 

Drill pipe.......... .......... Mud........................... 

Mud punps, repair and parts... 

Fishing tools................. 

Plugback cementing............ 

Logging....................... 

Fuel and oil.................. 

Supervisory................... 

Total.. ............ .. ..... Drilling : 

Labor bond.................... 

Total...................... 

Completion: 

Casing........................ 12,604.73 

Cenenting..................... 5,304.81 

Wellhead equipment............ 2,413.42 

Surface equipnent and meter 

-- 146,349.15 

- 342,149.54 

house........................ 6,116.05 

Downhole completion equipment. 8,950.55 

Total...................... 35,389.56 

Labor overhead (1.1514 x total I== 

labor)......................... 

Subtotal direct............ 

---- 22,100.00 

22,100 -00 

Fixed fee (7% of subtotal I 

direct12.. ........... .,., .. ..,, 85,162.29 

Total direct ............... INDIRECT 

-- 6,560.00 

23,147 -60 

Plant costs: 

Pickup and car rental......... 

Trailer rental................ 

Equipment repair and 

naintenance................. 

Water and tanks............... 

Telephone ..................... Sanitation and safety 

equipnent.................... 

Miscellaneous supplies and 

small tools.................. 

Hauling and shipping.......... 

Per diem...................... 

Electrical work............... 

Total...................... 

Fixed fee (7% of total plant 

24,793.53 

52,460.91 

'~xcludes startup, fishing, and end-of -projec t costs. 

2~p to a contract maximum of $119,713.00. 

-- 92,895.62 

244,441.03 

COS~S)~. ..................... Total indirect............. 

Grand total................ --- 

8,937.13 

. 145,840.90 

1,448,954.48 

- --- 196.35 

3,001.35 

53,875.51 

- 362.17 

5,536.00 

92,987.35 

576.17 -- 

8,807.14 

132,561.04 

7,802.44 

128,496.41 

1,169,530.58 
Table 7 shows an estimated cost for 

each of the five major drilling operations performed on EM-19. These costs 

were determined from the contractorls 

monthly invoices, which did not indicate 

the exact purpose of each item purchased. 

This means that each individual invoice 

had to be studied to determine the purpose of the items purchased and allow 

assignment of the cost to a particular 

operation. The care required to do this 

was exercised in the case of labor and 

such large and identifiable expenditures 

as the purchase of bits, water, mud, and 

directional drilling equipnent. However, 

where the purpose of an item was more 

difficult to determine (such as small 

tools and miscellaneous items), the costs 

have been assigned by time period. This 

means that the cost estimates of table 7 

are not exact. However, they should be 

within 10% of the actual costs. The cost 

estimated for the pilot hole drilling has 

been adjusted to remove the costs 

incurred during a period of 5 days when 

the rig engine broke down. However, no 

changes have been made to correct for the 

expenses and lost time caused by lostcirculation problems (appendix A gives 

the hours lost from this cause). Similarly the only costs removed from the 

estimate for the reaming are those for 

the bit crown fishing operation shown in 

the fishing costs colunn of table 6. 

Since the total fixed operating cost of 

the project (including fixed plant costs, 

labor, labor overhead, fixed fees, directional drilling equipnent, and the directional drillerls time) for a single working day was about $3,400 ($2,400 when 

reaming), even minor improvements could 

have a significant affect on the drilling 

cost. The change in the per meter costs 

of horizontal holes H1, H2, and H3 

reflects the improvements made in drilling technique during the project. The 

costs of H3 also reflect an extraordinarily long run of a Dyna-Drill tool. But 

it should be possible to maintain on a 

production basis a per meter horizontal 

drilling cost in the range of $100 to 

$115 ($30-$35/ft). 

TABLE 7. - Costs for EM-19 drilling 

operations 

Project Cost Summary 

Drilling 

operation 

Pilot ole' 

~eamin g2... 

Hl......... 

H2.. ....... H3......... 

The total cost of the Emerald Mine 

directional drilling contract (from 

September 1977 through May 1980) was 

$1,814,863.09 (table 8). The vertical 

dewatering hole cost $136,000.36. This 

includes the cost of drilling, casing, 

logging, jet slotting, hydraulic stimulation, and completion of the well for gas 

and water production. It does not 

include the cost of the pumping unit and 

the sucker rods that were obtained as 

surplus from another Government project. 

Drilling and completing the seven monitoring holes with water level sensing 

equipment cost a total of $217,877.23. 

The corehole drilled at the beginning of 

the project to determine the coal thickness and elevation cost $12,031.02. 

TABLE 8. - Proiect cost totals 

l~ost of 5 days lost tine due to rig engine breakdown not included. 

2~it crown fishing costs not included. 

Estimated 

cost 

$210,000 

330,000 

120,000 

150,000 

70,000 

Corehole................... $12,031.02 

Dewater hole (EM-20). ...... 136,000.36 

Monitor holes (EM-21-27) ... 217,877.23 

Directional hole (EM-19) ... 1,448,954.48 

Total................. 1,814,863.09 

Estimated Costs for a Production 

Distance 

drilled 

Directional Hole 

Cost 

m 

504 

491 

539 

377 

912 

In order to arrive at a reasonable 

cost estimate for drilling directional 

hole similar to EM-19, on a production 

basis, utilizing all of the improved 

techniques developed during the project, 

m 

$417 

672 

223 

154 

77 

ft 

1,652 

1,612 

1,767 

3,207 

2,993 

ft 

$127 

205 

68 

47 

23 
both a time and a cost estimate (in 1979 and the mud pumps are to be rented for 

dollars) have been developed. Table 9 the project. If those items of equipment 

gives a time estimate for a directional were purchased and used to drill other 

hole exactly like EM-19, assuming 1979 vertical and directional wells then their 

costs, no major fishing operations or purchase costs could be amortized over 

unusual lost-circulation problems, and several wells reducing the estimated cost 

assuming that the best equipment and for a single project. Based upon these 

techniques developed while drilling EM-19 estimates, a directional well exactly 

are to be used. Table 10 gives the cost like EM-19 could have been drilled 

estimate for this hole with the addi- and completed for slightly less than 

tional assumption that the drilling rig $1,000,000. 

TABLE 9. - Production hole time estimate1 

Task Days 

Mobilization and equipment set-up.............eeee...e 5 

Pilot ho1e........................................... 25 

 earni in^^ .............................................. 40 

Casing and ~enenting............~~.~~~~....~~.~..~~~.~ 4 

Drilling out plug...... ............................... 2 

Horizontal drilling: 

H1, 486 to 1,025 m (46 m/d)........ ................. 12 

HZ, 498 to 1,464 m (43 m/d).. ....................... 23 

H3, 498 to 1,398 n (43 m/d) ......................... 22 

Underreaming.. ee.e.~ee~ae~~e~~~e~ee~~eee~~~e~~eee~e~e

4 

Well completion.... ................................... 10 

Denobilizati~n.....~~..~..........~~~........~.~~~~.~. 5 

Total working days ............................... 152 

Off days... ........................................... 61 

Grand tota1..................................... 213 ---- 

l~ased upon a 24-hour day, 5 days per week. 

2~ncludes time to run and cement intermediate casing. 
TABLE 10 . . Production hole cost estimate 

(1979 dollars) 

DIRECT 

Labor : 

Nonsupervisoryl ......................................... Supervisory ............................................. Total ................................................ Drilling : 

Geolograph .............................................. Directional control equipment ........................... Directional drilling engineer ........................... Dyna-Drill .............................................. Rig rental .............................................. Drill pipe. bits and subs .............................. Mud ..................................................... Mud pumps. repair and parts ............................. 

f"llY COST~"'S~~~ cost 

Fishing tools ........................................... 5.000.00 

Plugback cementing ...................................... 0 

Logging ................................................. Fuel and oil ............................................ 13.680.00 

Labor bond .............................................. 3.851.00 

Total ................................................ Conple t ion : 

casing3 ................................................. 14.975.00 

cementing4 .............................................. 7.500.00 

Wellhead equipment ...................................... 2.413.42 

Surface equipnent and meter house ....................... 6.116.05 - 

Plant costs: 

Pickup and car rental ................................... Trailer rental .......................................... Equipment repair and maintenance ........................ Water and tanks ......................................... Telephone ............................................... Sanitation and safety equipnent ......................... Miscellaneous supplies and snall tools .................. 

Downhole coaplet ion equipment .......................... Total ................................................ Labor overhead (1.1514 x total labor) ................... Subtotal direct ...................................... Fixed fee (7% of subtotal direct) ....................... Total direct ......................................... INDIRECT 

4~ncludes cost of cenenting intermediate casing . 

NAp 

N Ap 

1.114.73 

NAp 

NAp 

NAp 

Hauling and shipping .................................... Per diem (rig superintendent) ........................... Electrical work ......................................... Total ................................................ Fixed fee (7% of total plant costs) ..................... Total indirect ....................................... Grand total .......................................... 

5~rimarily cost of submersible pump and cable. but not tubing . 

NAp 

NAp 

152 

NAp 

NAp 

NAp 

YAp Not applicable . Based upon a 24-hour. 3-shift day. 5 days per week (one driller and two helpers) . 2~ental of reaming pipe and purchase of 800 n of BQ wireline rod . 3~ncludes 130 m of intermediate casing not used in EM-19 . 

NAp 

9.00 

NAP 

NAp 

NAp 

NAp 

NAp 

8.950.55 

39.955.02 

169.438.64 

853.902.96 

59.773.21 

913.676.17 

NAP 

15 2 

NAp 

NAp 

NAp 

NAp 

NAp 

3.500.00 

1.368.00 

3.191.47 

44.494.83 

3.114.64 

47.609.47 

9619285.64 
CONCLUSIONS AND RECOMMENDATIONS 

A number of conclusions can be drawn 

from the Emerald Mine directional drilling project. It is technically feasible, 

with good directional control personnel, 

to quickly drill a directional pilot hole 

to a target coalbed. Thirty 24-hour days 

were required to drill the Emerald Mine 

pilot hole and approximately 12 days of 

downtime are included in this period. 

Once a target coalbed has been successfully intercepted, it is technically 

feasible to drill long horizontal methane 

drainage holes, and keep the holes in the 

coalbed. As experience was gained in 

directional control, it was possible to 

increase the horizontal drilling rate 

from 20.4 rn (67 ft) per day to 64.9 m 

(213 ft) per day, At the same time, the 

portion of the hole in coal increased 

from 62% to 92%. The longest horizontal 

hole drilled on the project (H2, fig. 1) 

reached a distance of 977.5 m (3,207 ft) 

from the end of casing. Based on the 

drilling experience at the Emerald Mine, 

it is believed that a horizontal hole 

could have been drilled significantly 

beyond the 977.5-m (3,207 ft) distance 

reached on HZ. The only impediment to 

drilling longer distances was the problem 

of caving of the holes drilled in shale 

near the bottom of casing, which prevented reentering the holes. 

It is still impossible to determine 

whether a directional hole is an economical method of draining methane from coalbeds since, as of late 1980, problems 

specific only to EM-19 have prevented the 

well from producing gas at what is 

believed to be its full potential. Once 

the remedial work has been done and gas 

production data has been obtained additional analyses will be made. 

The most important fact learned 

about horizontal and pilot hole drilling 

is that it is vital to confirm that the 

hole really is in the target coalbed. 

The accuracy of current well surveying equipment is at best '0.6 m (2-3 ft) 

vertically at the measured depth of 

EM-19, and many coalbeds are in the range 

of 1 to 3 m (3-10 ft) in thickness. In 

addit ion, experience with survey data 

from several directional holes (the 

Mather and EM-19 holes) indicates that 

the vertical depths indicated by the surveys are usually deeper than actual vertical depths of the holes. This makes 

correlation with vertical holes difficult. Indications of coal tops obtained 

from Dyna-Drill drilling rate changes and 

from cuttings can also be misleading, 

especially when drilling nearly horizontally across a Formation. Thus it 

appears that the only method to be certain that the hole is in the target coalbed is to drill well into it or even 

completely through it. 

--- Horizontal Drilling 

It was found that almost all portions of the horizontal holes drilled in 

rock would cave, making reentry diEficult 

or impossible when the drill pipe was 

removed. The portions of EM-19 drilled 

in roof and floor shales were a constant 

source of problems. In contrast, mall 

diameter (75-100 mm or 3-4 in) horizontal 

holes drilled in coal from within nines, 

have consistently been found to stay open 

for many years, except when drilled in 

stressed zones near mine openings. The 

best method developed in the Emerald 

drilling project to drill horizontal 

holes was to attempt to follow the 

regional dip of the coalbed and drill as 

rapidly as possible. When a hole left 

the coalbed, a sidetrack, either directly 

up or down, as required, was performed as 

soon as it was certain that the hole was 

really in rock (fig. 19). The sidetrack 

was started back far enough to provide 

sufficient distance to avoid immediately 

drilling out of the coalbed again. The 

optimum surveying interval for this horizontal drilling program was found to be 

between 12 and 18 m (40-60 ft). This 

program was used in drilling the last 

600 m (2,000 ft) of HZ and throughout the 

drilling of H3. 

It was found that in horizontal 

drilling, some type of additives to the 
drilling fluid are required for removal 

of cuttings and higher flow rates than 

can reasonably be run through the DynaDrill are required for cleaning the hole. 

It is recommended that a bypass valve 

capable of delivering 5.7 to 9.1 m3/h 

(25-30 gal/min) to the Dyna-Drill at differential pressures of 3,400 to 4,800 kPa 

(500-700 ~b/in~~) and bypassing an additional 14 m3/h (61 gal/min) he used to 

improve cuttings removal. 

Finally, it was learned during the 

horizontal drilling, that the BQ wireline 

rod used was not strong enough for this 

type of drilling. The boxes of the pipe 

began to open and the pins stretched 

until even a relatively small pull could 

separate the pipe at a tool joint. Fortunately, the highest tensile stresses 

are near the surface and separations usually took place above 180 m (600 ft) MD. 

It was relatively easy to screw back into 

the separated joint of pipe, pull it out 

of the hole, and remove it. However, by 

the end of the project approximately onehalf of the BQ pipe had been rejected as 

no longer suitable for further drilling. 

A better pipe for this work would perhaps 

be a 60-mm (2-318 in) 0.d. internal and 

external flush-joint casing or a tubing 

similar to BQ rod with the same wall 

thickness and internally flush-joint, but 

with a slight highly-tapered external 

upset to strengthen the connections. 

Reaming 

Both BCQ drill rod (56-m or 

2-3116-in 0.d.) and approximately 1 m 

(3 ft) long stingers were used to guide 

the reaming bits along the pilot hole 

path. It was found that the use of a 

stinger is the simpler, easier, cheaper, 

and safer of these two methods of 

following the pilot hole. However, precautions should be taken to insure that 

the pilot hole will stay open during 

reaming. These precautions should 

include the use of muds to prevent fluid 

loss to water-sensitive shales which 

could cause caving of the pilot hole. 

In order to reduce the problems 

of lost circulation, it might also be 

prudent to plan for the use of an intermediate casing string set below the local 

water table (since many directional 

drilling sites are likely to be on hilltops to obtain the required cover for 

drilling the circular arc). This could 

mean either splitting up the pilot hole 

drilling operation by stopping at the 

first casing point, and then reaming and 

setting the initial casing before finishing the pilot hole or simply reaming the 

hole in a larger size to the intermediate 

casing point. 

Bits 

It is recommended that diamond bits 

be used for all of the drilling operations. In particular the 76-m (3 in) 

diameter diamond deep cone bit SN-8S54000 

(table 3) was found to be very effective 

for horizontal drilling and allowed rapid 

side tracking. In general, the diamond 

bits were more efficient because of their 

long life and lower overall cost, due to 

their high salvage value (tables 3-4). 

The Strata-Pax bit designs used in this 

project are not recommended either for 

reaming or Dyna-Drill use unless significant improvements are made. Testing of 

tricone bits or hole openers for reaming 

work would also be worthwhile since even 

the diamond reaming bits were very inefficient and expensive. 
APPENDIX A.--EM-19, DETAILED TIME BREAKDOWN OF DRILLING OPERATIONS 

Drilling Operations. Time in Hours 

-.-. 

Operations 

. ...... Normal : 

Drilling or reaming ............ Surveying ...................... Rig maintenance ................ Circulating hole or lost circulation treatment .............. Plugback ....................... Pipe trip ...................... Startup & shut down ............ Mix mud & haul water ........... Wait on cement ................. 

7 .. 

Pilot 

hole 

262.5 

86 

3 

47 

0 

50.75 

6.25 

27.5 

13.75 

Stimulation treatment waiting 

time .......................... Waiting . 

........................ 33 

Off days and holidays .......... 544 336 

Total ....................... 1.137.25 1.073.25 

Downtime : 

Fishing ........................ Mud pumps ...................... Survey line and pump-down tool . Survey instrument .............. Dyna-Drill ..................... Pipe and bit failure ........... Rig ............................ 115.5 

Grand total ................. l~ishing operations primarily caused by a bit failure . Percent of Operating Time 

Downtime : . 

As a percentage of all time ......... Excluding off time .................. Drilling : 

As a percentage of all time ......... Excluding off time .................. Excluding off time and downtime.. ... Surveying : 

As a percentage of all time ......... Excluding off time .................. Excluding off time and downtime ..... 

I Pilot hole 

20 . 2 

26.9 

27.2 

36.2 

49.6 

8.9 

11.9 

16.2 

Reaming H1 Total 

22.9 

33.7 

20.6 

30.3 

45.6 

18.1 

11.9 

17.9 
APPENDIX B.--PROJECT CHRONOLOGY 

Directional Drilling for Degasif ication of the Pittsburgh Coalbed, 

Greene County, Pa., DOE Contract NO. ET-77-C-01-8891, 

Originally Bureau of Mines Contract 50377050 

Project Initiation and Site Preparation 

January 1976 Bureau of Mines began search for new drilling site after termination 

of Mather directional drilling project. 

Mar. 16, 1977 Drilling and directional control requests for proposals (RFP's) 

released for bid. 

Sept. 6,1977 CooperativeagreementsignedwithEmeraldMineCorp. 

Sept. 27, 1977 Drilling contract signed with Harold Fa Scott, Contractor. Original 

site at Emerald Mine not obtained because of problem with gas 

rights. 

Oct. 1, 1977 Contract transferred to DOE with project management remaining 

with Bureau of Mines. 

Oct. 27, 1977 Modification of contract signed to delay notice to proceed for 

approximately 90 days due to the Emerald Mines difficulty in finding a new site. 

December 1977- Coal strike precluded start of drilling operations because of reMarch 1978 quirement to use UMWA labor. 

Jan. 25, 1978 All responses to directional control RFP declared unacceptable. 

Feb. 21, 1975 Proposed modification to contract with Harold F. Scott, Contractor, 

to drill core hole, dewater hole, and subcontract directional control work, submitted to DOE Washington Office staff engineer. 

Apr. 7, 1978 Proposed modification to contract with Harold F. Scott, Contractor, 

to drill seven vertical monitoring holes subnitted to DOE Wasington 

Office staff engineer. 

May 1978 Emerald Mines Corp. secured acceptable drilling site. 

June 1978 Emerald Mine Corp. began preparation of drilling site. 

July 10, 1978 Notice to proceed on original drilling specifications received by 

Harold F. Scott, Contractor. Actual drilling operations could not 

proceed pending approval of contract modifications subnitted to the 

DOE, Feb. 21 and Apr. 7, 1978. 

Aug. 15, 1978 Contractor began mobilization of equipment to drilling site. 

Aug. 22, 1978 Contract with Harold F. Scott, Contractor, modified to include 

drilling a core hole, dewater hole, and subcontract directional 

control services. Cost: $385,498.37. (Time required for approval 

of contract modification, 6 months.) 
Core Hole Drilling 

Sept. 7, 1978 Contractor began drilling core hole at anticipated location of 

intercept of the Pittsburgh coalbed by the directional hole. 

Sept. 21, 1978 Core hole conpleted to a depth of 231 m (759 ft). 

Dewatering Hole Drilling 

Sept. 26, 1978 Contractor began drilling dewater hole with Government-owned drill 

rig near anticipated intercept of the Pittsburgh coalhed. 

Sept. 28, 1978 Contract with Harold Fa Scott, Contractor, modified to include the 

drilling of seven monitoring holes, cost: $443,196.35. (Time 

required for approval of contract modification, 5-112 months.) 

Oct. 11, 1978 Emerald Mines Corp. began site preparation for vertical monitoring 

holes. 

Oct. 18, 1978 Drilling of first vertical monitoring hole began. Dewater hole conpleted to depth of 274 m (900 ft). Casing (178-mm (7-in) 0.d.) run 

and cemented. 

Directional Hole Pilot Hole 

NOV. 1, 1978 Government-owned rig moved to and set up on directional drilling 

site. 

NOV. 2, 1978 Drilling operations on directional hole begun. 

NOV. 21, 1978 Casing jet-slotted adjacent to Pittsburgh coalbed in dewater hole. 

Dec. 19, 1978 Pilot hole (76-nn (3-in diameter)) to Pittsburgh coalbed completed 

to a total measured depth of 503 rn (1,649 ft) (305 m true vertical 

depth). 

Dec. 23, 1978- Project shut down for Christmas holiday. 

Jan. 2, 1979 

Reaminn Operation 

Jan. 8, 1979 Began overreaming directional hole from 76 to 222 mm (3 to 

8-314 in). 

Jan. 9, 1979 Directional hole reamed to 58 m (191 ft) MD. Severe lostcirculation problems. 

Jan. 15, 1979 Began reaming directional hole to 251-mm (9-718-in) diameter from 

surface to 34 m (110 ft) for installation of 244-mm (9-518-in) 

intermediate casing to control lost circulation. 

Jan. 23, 1979 Intermediate casing string parted while running to bottom, leaving 

9 m (30 ft) stuck in hole. 

Jan. 24, 1979 Began recovery operations for stuck casing. 

Jan. 26, 1979 Drilling and casing of seven vertical monitoring holes completed. 
Jan. 30, 1979 

Feb. 1, 1979 

Feb. 9, 1979 

Feb. 13, 1979 

Feb. 20, 1979 

Feb. 21, 1979 

Feb. 23, 1979 

Mar. 13, 1979 

Mar. 30, 1979 

Apr. 4, 1979 

Apr. 17, 1979 

Apr. 25, 1979 

May 4, 1979 

May 9, 1979 

May 10, 1979 

May 11, 1979 

May 14, 1979 

May 18, 1979 

May 24, 1979 

Retrieved 9 m (30 ft) of stuck 244-nn (9-518-in) casing. Ran 34 m 

(112 ft) of new 244-mm (9-518-in) casing in directional hole. 

Pulled worn Strata-Pax bit at 83 m (273 ft) and switched to diamond 

bit. 

"Backed off" BCQ wireline rod while pouring lost-circulation-control 

material in the hole. Began fishing operations to retrieve BCQ 

rod. 

Fished 39.6 m (130 ft) of BCQ rod from directional hole. Obtained 

core of Pittsburgh coalbed from vertical monitoring hole EM-21. 

Obtained core of Pittsburgh coalbed from vertical monitoring hole 

EM-22. 

Changed to flat-faced Strata-Pax bit at depth of 186 m (612 ft). 

Bit-crown separated from shank at 189 m (620 ft). Began fishing 

operations. 

Ran nil1 to grind up bit-crown. Mill cut 25.4-nm (1-in) pipe at 

about 36.6 m (120 ft). Began fishing operations for 25.4-mm (1-in) 

pipe and BCQ rod. 

Ran downhole TV camera. Removed main string of 25.4-mm (1-in) pipe 

and all of the BCQ wireline rod. 

Bit-crown speared and retrieved. 

Resumed reaming operations with third Strata-Pax bit, using stinger 

to guide it along the 76-mm (3-in) pilot hole. 

Strata-Pax bit removed at 257 m (842 ft) due to wear. Second diamond bit run. 

Obtained core of Pittsburgh coalbed from vertical monitoring hole 

EM-24. 

Obtained core of Pittsburgh coalbed from vertical monitoring hole 

EM-25. 

Reaming of directional hole completed at 491 m (1,612 ft). 

Ran 486 m (1,595 ft) of 140-mm (5-112-in) casing in directional 

hole. Obtained core of Pittsburgh coalbed from vertical monitoring 

hole EM-23. 

Casing cemented in directional hole. 

Casing plug drilled out. 

Drilled 27 m (90 ft) of 76-m (3-in) horizontal hole in preparation 

for hydraulic stimulation of EM-20. 

EM-20 hydraulically stimulated using 79 .5n3 (21,000 gal) foam 

treatment. 
Horizontal Hole Drilling 

May 28, 1979 

June 6-8, 1979 

June 14, 1979 

June 20, 1979 

June 26, 1979 

June 29, 1979 

June 30, 1979- 

July 8, 1979 

July 11, 1979 

July 13, 1979 

July 19, 1979 

July 20, 1979 

July 24, 1979 

July 25-26, 1979 

July 30, 1979 

Aug. 2, 1979 

Aug. 9, 1979 

Aug. 14, 1979 

Aug. 15, 1979 

Aug. 16, 1979 

Began drilling horizontal hole H1. 

Shut down while replacing rig clutch. H1 at 716.6 m (2,351 ft) 

MD . 

Drilled to 801.9 n (2,631 ft) MD. Pulled back to 674.2 m 

(2,212 ft) MD to sidetrack. 

Drilled to 808.3 m (2,652 ft) MD. 

Proposed modification of contract with Harold F. Scott, Contractor to recover funds expended during unanticipated fishing 

operations and lost circulation treatments submitted to DOE 

Washington Office staff engineer. 

Shut down for Independence Day. 

H1 reaches maximum depth of 1,024.7 m (3,362 ft) Mn. After pulling tools to change Dyna-Drill, could not get back into H1. 

Begin H2 at 491.3 m (1,612 ft) MD. 

H2 drilled to 701.6 m (2,302 it) MD. Pulled Dyna-Drill and could 

not get back to the bottom of H2. 

Began sidetrack of H2 at 604.1 m (1,982 ft) MD. 

H2 at 721.2 m (2,366 ft) MD. Dyna-Drill failed and tools pulled. 

Bit and rotating sub left in the hole. 

Fishing for bit. Bit left in the hole at 642.8 m (2,109 ft) MD 

in H2-2. 

Begin sidetrack H2-3 at 591.9 m (1,942 ft) MD. 

H2 passes 701 m (2,300 ft) Mn. 

Began cleaning the hole with Con-Det and Torque-Trim. 

H2 drilled to 1,030.8 m (3,382 ft) MD. Pulled tools when DynaDrill would not start. 

Could not get tools past 512.7 m (1,682 ft) MD. 

Washed drill string back into H2. 
Aug. 31, 1979 Completed hole H2 at 1,463.6 n (4,802 ft) MD. A total of 977.5 m 

(3,207 ft) of horizontal hole. 

Sept. 4, 1979 Begin sidetracking H3 at 497.4 m (1,632 ft) MD. 

Sept. 12, 1979 H3 at 927.2 m (3,042 ft) MD. 

Sept. 18, 1979 Contract with Harold F. Scott, Contractor, modified to recover 

funds expended during unanticipated fishing operations and lostcirculation treatments. Modification value: $244,764.26. (Time 

required for approval of contract modification, 2-314 months.) 

Sept. 21, 1979 H3 at total depth of 1,398.4 m (4,588 ft) MD. 

Sept. 26, 1979 H4 started at 488.3 m (1,602 ft) MD. 

Oct. 1, 1979 H4 terminated at 750.4 m (2,462 ft) MD. H5 started at 488.3 m 

(1,602 ft) MD. 

Oct. 5, 1979 H5 terminated at 701.6 m (2,302 ft) MD. 

Underreaming 

Oct. 8-9, 1979 EM-19 opened from 76 to 216 mn (3 to 8-112 in) between 486.2 and 

531 m (1,595-1,742 ft) MD. Hole entered coal at 522 m (1,712 ft) 

MD. 

We1 1 Completion Work 

Oct. 10, 1979 Proposed modification to contract with Harold F. Scott, Contractor, for a no-cost time extension to May 26, 1980, submitted to 

DOE Methane from Coalbeds project manager, Morgantown, W. Va. 

Oct. 15-20, 1979 Cleaned out and bailed water from EM-20. 

Oct. 22-26, 1979 Bailed and swabbed EM-20. 

Oct. 26, 1979 Contract with Harold F. Scott, Contractor, modified for a nocost time extension to May 26, 1980. (Time required for approval 

of contract modification, 16 days.) 

Nov. 5, 1979 Ran tubing and rods in EM-20. 

Nov. 6-7, 1979 Pumped EM-20 with spudding rig. Installed EM-19 wellhead. 

Nov. 9, 1979 Set punping unit on EM-20. 

Nov. 15, 1979 Mine hooked up power lines to EM-20. Begin pumping water at 

20.4 n3/d (128 bbl/d). 

Well Testing and Production 

Dec. 4-7, 1979 Attempted to circulate water in EM-19 to clean up well and increase water production at EM-20. 
Dec. 17-19, 1979 

Dec. 20-21, 1979 

Dec. 27, 1979 

Dec. 28, 1979 

Jan. 2, 1980 

Jan. 3, 1980 

Jan. 4, 1980 

Jan. 7-8, 1980 

Jan. 9, 1980 

Jan 10, 1980 

Jan. 11, 1980 

Jan. 14, 1980 

Jan. 15, 1980 

Jan. 16, 1980 

Jan. 17, 1980 

Pumped water into EM-20 at up to 8,860 kPa (1,285 ~b/in~~) and 

0.15 to 0.3 n3/min (1-2 bhljnin) in attempt to fracture the coal 

and move cuttings to EM-19. Circulate water at EM-19 to remove 

cuttings. 

Using compressed-air l.ift to dewater EM-19. EM-20's sucker rod 

pump also pumping. 

Working on EM-19 wellhead equipment. 

Set up flare stack for EM-19. 

Completed EM-19 flare stack. Ran BQ rod to 335 m (1,100 ft) in 

EM-19 to air lift water from the hole. Began air lift at 

1245 hours. Shut down at 1530 hours. 

Blowing water from EM-19 between 0800 and 1600 hours. Ran BQ rod 

to 515 m (1,690 ft) MD (in the open hole). Putting up the flare 

stack on EM-20. 

Blowing water fron EM-19 between 0800 and 1600 hours. Completed 

installing flare stack on EM-20. 

Blowing water from EM-19 between 0800 and 1600 hours. Pulled pipe 

back to 484.6 m (1,590 ft). 

Blowing water from EM-19 (0800 to 1600 hours). Installed float 

water-level sensor in EM-27. 

Blowing water from EM-19 (0800 to 1600 hours). Total production, 

approximately 40 m3 (250 bbl). Float devices hooked up on EM-21, 

25, and 26. 

Blowing water from EM-19 (0800-1600 hours). Floats hooked up on 

EM-22, 23, and 24. 

Blowing water from EM-19 (0800 to 1600 hours). Total production 

58 m3 (365 bbl). Pulled pump and rods fron EM-20. Pumped 

approximately 36 m3 (225 bbl) of water into EM-20 at 6,500 to 

6,890 kPa (950-1,000 ~b/in~~) surface pressure between 1145 and 

1338 hours. 

Blowing water fron EM-19 (0800 to 1600 hours). Total production 

46.6 m3 (293 bbl). Pumped approximately 71.5 m3 (450 bbl) of 

water into EM-20 at 6,200 to 7,240 kPa (900-1,050 lb~in~~) surface pressure, between 0935 and 1500 hours. 

Blowing water from EM-19 (0800 to 1600 hours). Ran pipe to 

515.1 m (1,690 ft) MD. Pumped approximately 79 m3 (500 bbl) of 

water into EM-20 between 0900 and 1500 hours. 

Blowing water from EM-19 (0800 to 1600 hours). Total production 

62 m3 (392 bbl). Pulled BQ rod back to 457.2 m (1,500 ft) MD. 

Ran punp and rods hack into EM-20, and put it back on water 

production. 
Jan. 18, 1980 

Jan. 21, 1980 

Jan. 22, 1980 

Jan. 23, 1980 

Jan. 24, 1980 

Jan. 25, 1980 

Jan. 28, 1980 

Feb. 4, 1980 

Feb. 5, 1980 

Feb. 6, 1980 

Feb. 7, 1980 

Feb. 8, 1980 

Feb. 11, 1980 

Feb. 12, 1980 

Feb. 13, 1980 

Feb. 15, 1980 

Blowing water from EM-19 (0800 to 1600 hours). Total production 

51 m3 (319 bbl). EM-20 gas production 59 n3/d (2,080 ft3/d), 

water 16.4 n3/d (103 bbl/d). Well not yet pumped down. 

Blowing water from EM-19 (0800 to 1600 hours). Total 33 m3 

(207 bbl). EM-20 gas flow 218 m3/d (7,720 ft3/d), water 7.3 m3/d 

(46 bbl/d). 

Start blowing EM-19 around the clock at 0001. Total for 24 hours, 

78 m3 (491 bbl). EM-20 gas production 153 m3/d (5,400 ft3/d), 

water 2.1 m3/d ( 13 bbl/d). 

Blowing water from EM-19 (24 hours). Total production 51 m3 

(321 bbl). 

Blowing water from EM-19 (24 hours). Total production, 39 m3 

(247 bbl). EM-20 gas flow 251 m3/d (8,870 ft3/d), water 1 m3/d 

(6 bbl/d). 

Blowing EM-19 until 1100 hours. Total water production, 19n3 

(119 bbl). Pulled BQ rod out of the hole at 1110 hours. EM-20 

gas flow 323 m3/d (11,400 ft3/d), water 1 m3/d (6 bbl/d). 

EM-20 production, gas 137 m3/d (4,850 ft3/d), water 5 m3/d 

(31.6 bbl/d). 

Ran BQ rod in EM-19. 

Blowing water from EM-19, 1220 to 1600 hours. EM-20 gas flow 

66 m3/d (2,320 ft3/d), water 4.7 m3/d (29.4 bbl/d). 

Blowing EM-19, 0845 to 2400 hours. Total water production 53 m3 

(336 bbl). EM-20 gas flow 131 m3/d (4,650 ft3/d), water 

3.1 m3/d (19.5 bbl/d). 

Blowing EM-19 (24 hours). Total water production 52 m3 (330 bbl). 

EM-20 punp, rods, and tubing pulled at 1120 hours. 

Blowing EM-19 until 1530 hours. Pumped water into EM-20, 1034 to 

1142 hours and 1259 to 1415 hours at 1.6 to 2.4 n3/h (10-15 bbl/ 

min). Maxinun surface pressure 9,860 kPa (1,430 1b/inzg), average pressure 8,600 kPa (1,250 1b/inzg). Total volume pumped 

217 m3 (1,363 bbl). 

Put pump back in EM-20. Pump on continuously through 

May 31, 1980. 

EM-20 gas flow 64 m3/d (2,270 ft3/d), water 20.4 m3/d 

( 128.5 bbl/d) . 

Emerald Mine begins punping water from No. 2 return shaft near 

EM-25. Depth to Pittsburgh coal 189 m (620 ft). 

Air shaft water level down 11 m (35 feet) from surface. 
Feb. 19, 1980 

Feb. 21, 1980 

Feb. 24-29, 1980 

Feb. 25, 1980 

Feb. 26, 1980 

Feb. 27, 1980 

Feb. 28, 1980 

Feb. 29, 1980 

Mar. 3, 1980 

Mar. 4, 1980 

Mar. 13, 1980 

Mar. 14, 1980 

Mar. 15, 1980 

Mar. 17, 1980 

Mar. 18, 1980 

Mar. 19, 1980 

Mar. 20, 1980 

EM-20 gas flow 104 n3/d (3,670 ft3/d), water 14.9 n3/d 

(93.5 bbl/d). Shaft water level 61 m (200 ft). 

Increase stroke rate on EM-20 punp from 14 to 15-112 strokes ger mi-nute. Water production not affected. EM-20 gas flow 141 m /d 

(4,980 ft3/d), water 14.9 n3/d (93.5 bbl/d). 

EM-25 water level begins to drop due to shaft dewatering. 

Shaft water level 105 m (345 ft) at 2330 hours. EM-20 gas flow 

114 m3/d (4,030 ft3/d), water 9.1 m3/d (57 bbl/d). 

Reduce EM-20 stroke rate back to 14 strokes per minute. Shaft 

water level 114 m (374 ft) below surface. 

Shaft water level 121 m (398 ft) at 1530 hours. EM-20 gas flow 

37 m3/d (1,310 ft3/d), water 9.3 n3/d (58.8 bbl/d). 

Shaft water level 145 m (475 ft) at 2000 tlours. EM-20 gas flow 

78 m3/d (2,760 ft3/d), water 8.8 n3/d (55.6 bbl/d). 

Shaft water level 142 m (465 f t). EM-20 gas flow 110 m3/d 

(3,890 ft3/d), water 7.9 m3/d (50 bbl/d). 

Bailing muck frorn air shaft, water level 152 m (500 ft). 

Shaft water level 168 m (550 ft). EM-20 gas flow 118 n3/d 

(4,160 ft3/d), water 7.8 m3/d (49 bbl/d). 

Ordered submersible pump for EM-19. EM-20 gas flow 132 m3/d 

(4,650 ft3/d), water 6.4 n3/d (40.3 bbl/d). 

Air shaft dewatered to the Pittsburgh coalbed, at 189 m (620 ft). 

Water level in EM-19, 130 n (430 ft) above the Pittsburgh coalbed, or about 1,280 kPa (186 1b/in2g). 

Air shaft cut into by mining from 1 West return section. 

Swabbing rig cloved to EM-24. Begin swabbing at 1055 hours with 

initial swabbing depth 51.5 m (168.9 ft). Removed 2.4 m3 

(640 gal) from hole by 1600 hours, 1.2 m3 (327 gal) of which was 

in the casing initially. EM-20 gas flow 141 m3/d (4,980 ft3/d), 

water 6.1 m3/d (38.5 bbl/d). 

Initial water level in EM-24, 59.4 m (195 ft). Swabbed 1.9 m3 

(500 gal). EM-20 gas flow 133 m3/d (4, 710 ft3/d), water 

6.2 n3/d (38.8 bbl/d). 

Initial water level in EM-24, 152 m (500 ft). Swabbed 0.5 m3 

(120 gal) and shut down after 1200 hours so that the pressure reductions caused by the air shaft could be determined. 

Filled EM-24 and put the water level sensor back on. EM-20 gas 

flow 141 m3/d (4,980 ft3/d), water 6.3 m3/d (39.6 bbl/d). EM-19 

gas flow zero. 
Mar. 21, 1980 

Mar. 24, 1980 

Mar. 26, 1980 

Mar. 27, 1980 

Apr. 1, 1980 

Apr. 8, 1980 

Apr. 15, 1980 

Apr. 23, 1980 

Apr. 28, 1980 

Apr. 29, 1980 

May 5, 1980 

May 7, 1980 

May 8, 1980 

May 9, 1980 

May 12, 1980 

May 14, 1980 

EM-20 gas flow 147 m3/d (5,200 ft3/d) water 5.6 m3/d 3 (35.5 bbl/d). EM-19 gas flow 25 m3/d (872 ft Id). 

EM-20 gas flow 309 m3/d (10,900 ft3/d), water 6.5 n3/d (41 bbl/d). 

EM-19 gas flow 79 m3/d (2,800 ft3/d). 

EM-20 gas flow 277 m3/d (9,800 ft3/d), water 6.3 m3/d 

(39.7 bbl/d). EM-19 gas flow 66 n3/d (2,320 ft3). 

EM-20 gas flow 272 m3/d (9,600 ft3/d), water 6.0 m3/d (38 bbl/d). 

EM-19 gas flow 63 m3/d (2,210 ft3/d). 

EM-20 gas flow 283 m3/d (10,000 ft3/d), water 5.9 n3/d 

(37.4 bbl/d). EM-19 gas flow 61 m3/d (2,160 ft3/d). Ditch dug 

to run power line to EM-19 wellhead for the submersible pump. 

EM-20 gas flow 294 m3/d (10,370 ft3/d), water 5.3m3/d 

(33.2 bbl/d). EM-19 gas flow 73 m3/d (2,570 ft3/d). 

EM-20 gas flow 304 m3/d (10,730ft3/d), water 5.0 m3/d 

(31.6 bbl/d). EM-19 gas flow 76 n3/d (2,670 ft3/d). 

Submersible pump, cable, and control box delivered to EM-19 drilling site. EM-20 gas flow 314 m3/d (11,080 ft3/d), water 4.9 n3/d 

(30.7 bbl/d). EM-19 gas flow 79 m3/d (2,800 ft3/d). 

Submersible pump run in directional hole. 

Submersible pump pulled from hole. Wires cut by centralizer. 

EM-20 gas flow 342m3/d (12,080 ft3/d), water 4.5m3/d 

(28.2 bbl/d). EM-19 gas flow not measured. 

Submersible pump run again. Splice leaked and shorted out pump 

after 1 hour of operation. 

Respliced submersible pump cable. EM-20 gas flow 384 m3/d 

(13,580 ft3/d), water 4.2 m3/d (26.7 bbl/d). EM-19 gas flow 

83 m3/d (2,940 ft3/d). 

Pump run in EM-19 and check valve broke at 36 m (120 ft). Pump 

pulled from the hole using the cable. 

Prepared to run pump in EM-19 but found that the motor seals had 

failed when check valve broke and put tension on the cable. 

Motor sent to REDA Colunbus repair facility to be resealed. A new 

motor also purchased. EM-20 gas flow 388 m3/d (13,720 ft3/d), 

water flow 4.3 m3/d (27 bbl/d). EM-19 gas flow 72 m3/d 

(2,550 ft3/d). 

Submersible pump run in EM-19. Initial water flow 2.6 m3/h 

(11.5 gal/min). EM-20 gas flow 392 m3/d (13,860 ft3/d), water 

flow 3.9 m3/d (24.5 bbl/d). EM-19 gas flow 69 m3/d 

(2,430 ft3/d). 
May 15-16, 1980 Pump run during daylight hours only for testing purposes. During 

this period it was found that gas entering the pump was causing 

it to shut off without pumping the hole dry. At the end of the 

16th the pump was put on full time operation. 

May 19, 1980 EM-20 gas flow 469 m3/d (16,580 ft3/d), water 3.4m3/d 

(21.4 bbl/d). EM-19 gas flow rates not measured. 

May 20, 1980 EM-20 gas flow 452 m3/d (15,980 ft3/d), water 3.5 m3/d 

(21.7 bbl/d). EM-19 gas flow 141 m3/d (4,980 ft3/d), water flow 

intermittent but less than 1.6 m3/d (10 bbl/d). 

May 23, 1980 Last working day of contract. All equipment keys, etc., turned 

over to Government. 

May 30, 1980 EM-20 gas flow 452 m3/d (15,980 ft3/d), water 3.6 m3/d 

(22.8 bbl/d). EM-19 gas flow 157 m3/d (5,540 ft3/d), water flow 

1 .0 m3/d (6 bbl/d). 

IIU.S. GOVERNMENT PRINTING OFFICE. 1982 - 505 - 002/20