AUTOMATED MUDLOGGING SYSTEMSmudlogger.com/resources/AMS 11-16-01 RMAG Donovan.pdf · AUTOMATED...

AUTOMATED MUDLOGGING SYSTEMS 780 EAST PHILLIPS DRIVE SOUTH

LITTLETON, CO 80122 [email protected] E-mail www.mudlogger.com Website

(303) 794-7470 Office (303) 794-4838 Fax

Friday, November 30, 2001 This material was presented at the Rocky Mountain Association of Geologist meeting November 16, 2001. The topic was COAL BED METHANE GAS CONTENT DETERMINED BY MUDLOGGING METHODS , copyrighted 2001 by Donovan Brothers Incorporated. SLIDE A, PAGE 4. No explanation needed. SLIDE B, PAGE 5. Organization of talk. SLIDE C, PAGE 6. No explanation needed. SLIDE D, E, F, PAGE 7, 8, 9. The Clay #1 in the San Juan Basin was completed by Dugan Production Corp.. Three feet of coal produced over 1.2 BCF of gas. This illustrates the high gas storage capacity of coals. Also note this was a water free completion, which dispels the commonly held belief that all coal wells produce water. Finally one should not discount any coal due to being to thin, not being the right rank, not being the right formation, not being at the right depth, or not being in the right Basin. Be open to all the possibilities of this newly found resource. SLIDE G, H, I, PAGE 10, 11, 12. These slides show the results on the Western side of the Powder River Basin. The scatter in slide G, page 7 may be due to other factors such as permeability and reservoir water drive. Not withstanding a correlation exists and demonstrates this is a good tool for determining gas content. Also note the gas content calculated is 2 to 7 time greater than the “accepted” gas content values. Slide H, page 8 indicates good wells make less water, at least in the first 6 months. Slide I, page 9 indicates some wells with high water production also have gas. This may be problematic due to high lifting costs. SLIDE J, PAGE 13. No explanation needed. SLIDE K, PAGE 14. Stress assumption 3 SLIDE L, PAGE 15. Cuttings are small and desorb like whole cores. One dimension, the cutting height can be determined and therefore the worst-case scenario can be determined. The worst-case scenario is the slowest release of gas from the cuttings. The slowest release occurs when the cutting height is the smallest dimension relative to the other cutting dimensions. It is important to note that by changing controllable drilling parameters the cuttings can be made smaller thus allowing for gas to rapidly escape.

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Studies of cuttings indicate they are smaller than calculated possibly due to disaggregation while traveling to the surface. SLIDE M, PAGE 16. Note how small cuttings are SLIDE N, PAGE 17. The theoretical basis for mudlogging gas content determination is base on desorption data. Desorption data is based on the flow regimes from coal into a conduit like a well or fracture. Slide N, page 14 show the four flow regimes. Whole core desorption uses formation linear flow, regime 3 to determine lost gas. This may understate “lost gas” because regimes 1 and 2 are not accounted. SLIDE O, PAGE 18. This slide demonstrates the potential magnitude of the error. This data is plotted on square root of time which is typical for lost gas determination. Note flow regimes 1 and 2 give off gas at early times. Lost gas may be understated in conventional whole core desorption data. SLIDE P, PAGE 19. This is an example of whole core desorption data plotted on a linear time scale. Note two interesting portions of the curve early and late. Note most gas exits the core rapidly at the start of desorption. Also note that less and less per period of time desorbs at late times. This is problematic for conventional core desorption because early time data is not available and is corrected by “lost gas” calculations. In the late time period less and less gas is expelled which is good for mudlogging determinations because it is assumed that cuttings are so small they release gas rapidly. Also note the late time phenomena is well known because it has been documented by numerous core desorption studies. SLIDE Q, PAGE 20. This is how core desorption data is related to cutting and mudlogging gas content determinations. The amount of gas desorbed over time and at certain times is known. The diameter of the core is known and the height of the cutting is known. If it is assumed that the cutting height is a diameter then the amount of gas released at a certain time after drilling coal can be determined by dimensional analysis. Also not again the variability in “lost gas” between accepted methods, which ranges from 91 to 372 SCF in this example. SLIDE R, PAGE 21. If the desorption profile for a 4 inch core is used for a 0.1 inch cutting the time required for a certain percentage of gas release can be determine. It takes about 16 hours (960 minutes) to release 80% of the gas in a 4 inch core. A cutting in this example is 0.1 inch or one fortieth of the diameter of the whole core(0.10/4.00). One fortieth of 960 minutes is 24 minutes. Therefore it takes 24 minutes to release 80% of th gas from a 0.1 inch diameter cutting. If the core were 0.05 inches in diameter it would take 12 minutes to release 80% of the gas in the coal cutting. The process is accelerated by turbulence and disaggregation as the cutting coming up the hole and through the gas trap. To release over 50% of the gas it takes considerably less time. The time to release the gas is well within the typical circulation times.


SLIDE S, T, PAGE 22, 23, 24, 25. This is an example of the influence of free gas in coal pores and fractures. If the matrix density of the coal is can be determined in a laboratory and the bulk density of the coal can be measured from the density log then the free gas porosity can be determined. The calculations indicated that high gas content has more influence on reserves than free gas at shallow depths. Coal does not typically have the free gas porosities needed for large reserves. Also if free gas porosity was a common phenomenon then initial water production should be low because gas would in the high permeability pores and fractures. SLIDE U, V, W, X, Y, PAGE 26, 27, 28, 29, 30. This is the air drilling example. Note the gas reading on Slide V, page 24 is the definition of a “unit”. Very low gas readings yield good gas content values in air drilling. The chart on Slide Y, page 27 confirms the above assertion. SLIDE Z, AA, AB, AC, PAGE 31, 32, 33, 34. This is the mud drilling example. Note to use this technique measured amounts of calcium carbide must be used. IF CALCIUM CARBIDE DATA IS NOT OBTAINED WHILE DRILLING THE WELL THEN CALCULATING GAS CONTENT FROM MUDLOGGING DATA IS VERY TENUOUS. Note that generally better shows for the same coal gas content are found when drilling with mud. If you have any questions or comments contact us by calling (303) 794-7470 or by e-mail at [email protected]. This material is copyrighted. Thank you for allowing us to present this data. Sincerely, Bill Donovan


mailto:[email protected]

COAL BED METHANE GAS CONTENTDETERMINED BY MUDLOGGING METHODS

BYBILL DONOVAN

AUTOMATED MUDLOGGING SYSTEMS

780 E. PHILLIPS DR. SLITTLETON, CO 80122

(303) 794-7470 VOICE(303) 794-4838 FAX

[email protected] E-MAILWWW.mudlogger.com WEBSITE

WE DON'T PASS GAS


OUTLINE

1) INTRODUCTION

2) ACKNOWLEDGEMENTS

3) RESULTS

4) OBJECTIVE AND PURPOSE

5) ASSUMPTIONS

6) AIR DRILLING EXAMPLE

7) MUD DRILLING EXAMPLE

8) SUMMARY


I WOULD LIKE TO ACKNOWLEDGEAND THANK

THE FOLLOWING PEOPLE

SCOTT ZIMMERMAN, JM HUBER CORP.BRIAN HUGHES

JM HUBER's STAFF IN SHERIDAN AND DENVERTOM DUGAN, DUGAN PRODUCTION CORP.

DR. DOUG HILCHIEMARK ERICKSON, PANNONIAN OIL AND GAS CORP.

ROGER HIVELY, GEOLOGISTSTEVE CHAPMAN, GEOLOGIST

MIKE ALLRED AND JACK MCDERMOTT, GEOLOGISTS

JM HUBER CORP.GAS CONTENT VS GAS PRODUCTION

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JM HUBER CORP.GAS PRODUCTION VS W/G RATIO

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180 DAY GAS PRODUCTION (MCF)

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JM HUBER CORP.GAS CONTENT VS WATER/GAS RATIO

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OBJECTIVE AND PURPOSEOBJECTIVE

MEASURE THE GAS CONTENT OF DRILLED COALS AND REPORTAS STANDARD CUBIC FEET OF GAS PER TON OF COAL

PURPOSE

1) EVALUATE ONE OF THREE MAJOR FACTORS REQUIRED FOR A SUCCESSFUL CBM PROJECT (GAS, PERMEABILITY AND WATER)2) PRESENT MUDLOGGING GAS DATA IN A FORMAT TYPICAL TO THE CBM INDUSTRY (GAS CONTENT IN SCF/CUBIC FEET)3) HELP PREDICT FUTURE WELL PERFORMANCE4) NORMALIZE AND RANK COAL ZONES IN THE SAME WELL5) NORMALIZE AND RANK COAL ZONES IN DIFFERENT WELLS THAT WERE DRILLED BY DIFFERENT METHODS6) COMPARE RESULTS FROM DIFFERENT METHODS USED TO DETERMINE GAS CONTENT7) EVALUATE WORKOVER CANDIDATES8) INEXPENSIVE DATA IF MUDLOGGING IS ALL READY USED9) QUALITY CONTROL CHECK ON MUDLOGGING PERFORMANCE10) HELP TOPSETTING BY ACCURATELY DETERMINING DRILL RATE AND BOTTOMS UP TIME11) HELP TOPSETTING BY HAVING A THIRD FACTOR CONFIRMING THE COAL (DRILLING RATE, SAMPLE AND GAS DATA)12) SEMI QUANTITATIVE COAL EVALUATION: TYPE 1 COAL, SHOW AND AFTER FLOW INDICATES GAS PRESENT, PERMEABILITY AND RESERVOIR PRESSURE NEAR HYDROSTATIC PRESSURE TYPE 2 COAL, SHOW AND NO AFTER FLOW INDICATES GAS PRESENT BUT LOW PERMEABILITY OR LOW RESERVOIR PRESSURE OR BOTH TYPE 3 COAL NO SHOW INDICATES LIMITED CBM POTENTIAL13) MONITOR AND KEEP A RECORD OF DRILLING OPERATIONS14) PART OF A WELL SAFETY PROGRAM


ASSUMPTIONS1) DRILLED COAL VOLUME AND DENSITY CAN BE DETERMINED

A) DRILLING RATE MUST BE ACCURATELY MEASURED B) BIT DIAMETER MUST BE KNOWN C) DENSITY CAN BE MEASURED FROM CUTTINGS, DENSITY LOG, CORE DATA OR MINE DATA

2) NO FORMATION FLUIDS (GAS, OIL OR WATER) OR DRILLING FLUID FLOW BETWEEN WELLBORE AND FORMATION A) GAS IS NOT FLUSHED IN FRONT OF THE BIT OR LATERALLY WHILE DRILLED BECAUSE SORPTION IS NOT A PRESSURE MECHANISM B) DRILLING IS TYPICALLY FAST ENOUGH TO PREVENT FLUSHING C) ASSUMES WELL IS NOT LOSING CIRCULATION OR KICKING

3) GAS ESCAPES CUTTINGS PRIOR TO MEASUREMENT

A) ASSUMES HEIGHT OF CUTTING CAN BE DETERMINED B) ASSUMES CUTTINGS ARE LIKE VERY SMALL CORES AND DESORB WITH THE SAME DRIVE MECHANISMS

4) THE GAS TRAP LIBERATES AND DETECTORS MEASURE THE PERCENTAGE AND VOLUME OF GAS EXITING WELLBORE

A) GAS TRAPS CAN BE "CALIBRATED" WITH CARBIDE LAGS B) PUMP VOLUMES ARE STABLE AND KNOWN TO DETERMINE "SWEEP RATES"

5) DRILLING FLUID DOESN'T INTERACT WITH HYDROCARBON GASES

A) SOME POLYMERS DAMAGE COALS AND HOLD BOTH METHANE AND ACETYLENE IN THE DRILLING FLUID B) GAS IS TRANSPORTED WITHOUT BEING DISPERSED VERTICALLY AS IT TRAVELS UP THE ANNULUS

4 X CH

CH = 12 X CH

2 X CH

CH = 1

1/2 X CHMIDDLE

CASE

ANALOGYDRILLING IS ANALOGOUS TO AA MILLING MACHINE THE CUTTER,FEED RATE AND ROTARY SPEEDDETERMINES THE THICKNESS OF THESHAVING PRODUCED

FORMULACH = 12.0/(PR X ROT X CUT) CH = CUTTING HEIGHT (inches) PR = PENETRATION RATE (minute/foot) ROT = BIT ROTATION (revolutions/minute) CUT = CONES OR CUTTERS (cutters per revolutions)

EXAMPLEPR = 0.5 minutes/footROT = 160 revolutions/minuteCUT = 3 cutters per revolutionsCH = 12.0/(0.5 X 160 X 3) = 0.05 inches

DISCUSSION

1/4 CH

CH = 1

1/2 CH

BESTCASE

WORST CASE USED FOR GAS CONTENT CALCULATIONSIF CUTTINGS SMALLER LIBERATION IS QUICKERCUTTINGS FURTHER ARE ABRADED, CRUSHED ANDDISSOLVED AS THEY ARE CIRCULATED OUT OF THE HOLE

WORSTCASE

CUTTING HEIGHT DISCUSSIONPURPOSEDETERMINE CUTTING HEIGHT ANDSIZE FOR:1) CONTROLLING CUTTING SIZE BY ADJUSTINGRPM'S, CUTTER AND WOB2) VALIDATING THE MUDLOGGING GASCONTENT ASSUMPTION THATGAS IS LIBERATED FROM COAL RAPIDLYWHEN CRUSHED BY A DRILL BIT3) CUTTING SIZE IS AN IMPORTANTFACTOR IN CUTTING TRANSPORT4) VISUAL SAMPLE EXAMINATIONIS ENHANCED WHEN CUTTINGS ANDCAVINGS CAN BE SEPARATED BY SIZE

UPHOLE

VISUAL REPRESENTATIONof a WHOLE CORE and

DRILL CUTTINGS DIAMETERS

0.10 INCH DIAMETERDRILL CUTTING

0.05 INCH DIAMETERDRILL CUTTING

4.00 INCH DIAMETERWHOLE CORE

CUTTING SIZE CAN BE CONTROLLED TO MAKE SMALLERCUTTINGS BY:1) DECREASING THE PENETRATION RATE (PR) BY REDUCING THE WEIGHT ON BIT (WOB)2) INCREASING THE BIT ROTATION (ROT) BY INCREASING THE ROTARY TABLE SPEED, USING A MUD MOTOR OR BOTH3) INCREASING THE NUMBER OF CUTTERS (CUT) BY USING PDC OR HAMMER TYPE BITS

LOST GAS PROBLEMRED FRACTURE LINEAR REGIME, PURPLE BI LINEAR REGIME AND BLUE FORMATION

LINEAR REGIME (NOTE AMOUNT OF GAS LIBERATED IN VERY EARLY TIMES)

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F/TO

N)

Series1Series2Series3

WSD AUTOMATED MUDLOGGING SYSTEMS11/29/01 780 E. PHILLIPS DR. S.8:31 PM LITTLETON, CO 80122

(303) 794-7470 OFFICE, (303) 794-4838 FAX, [email protected] EMAIL

Assume only methane gas in porosityAssume Z factor is 1Assume hydrostatic gradient is 0.433 psi/footAssume geothermal gradient of 1 degree F/100 feetAssume mean surface temperature of 70 degrees FAdsorbed gas is gas in coalFree gas is gas in cleats, fractures or any pore spaceEnter shaded data

COAL DEPTH: 600 FEETRESERVOIR PRESSURE % OF HYDROSTATIC: 100% OF 0.433 PSI/FOOT OF DEPTH

RESERVOIR TEMPERATURE % OF GEOTHERMAL: 100% OF 1 DEGREE F/100 FEET OF DEPTHCOAL GRAIN DENSITY: 1.31 GMS/CC OF COAL ONLYCOAL GAS CONTENT: 150 SCF/TON ADSORBED GAS

COAL THICKNESS: 20 FEETCOAL DRAINAGE AREA: 40 ACRES

COAL RESERVOIR PRESSURE: 275 PSIA 18.67347 ATMCOAL RESERVOIR TEMPERATURE: 76 DEGREES FAHRENHEIT 24.44444 C

METHANE DENSITY AT RESERVOIR CONDITIONS: 0.0122 GMS/CC

TONS OF TOTAL ADSORBED FREE GAS ADSORBED FREE GASCOAL COAL BULK COAL/ COAL GAS SCF OF GAS/ SCF OF GAS/ COAL GAS COAL GASPOROSITY DENSITY BULK RES CF CONTENT BULK RES CF BULK RES CF CONTENT CONTENT(%) (GMS/CC) (TONS/RES CF) (SCF/TON) (SCF/RES CF) (SCF/RES CF) (% GAS/RES CF) (% GAS/RES CF)

0% 1.31 0.0409 150 6.1 0.0 100% 0%1% 1.30 0.0405 155 6.1 0.2 97% 3%2% 1.28 0.0401 159 6.0 0.4 94% 6%3% 1.27 0.0397 164 6.0 0.6 91% 9%4% 1.26 0.0393 169 5.9 0.7 89% 11%5% 1.25 0.0389 174 5.8 0.9 86% 14%6% 1.23 0.0385 179 5.8 1.1 84% 16%7% 1.22 0.0381 184 5.7 1.3 81% 19%8% 1.21 0.0376 190 5.6 1.5 79% 21%9% 1.19 0.0372 195 5.6 1.7 77% 23%

10% 1.18 0.0368 201 5.5 1.9 75% 25%11% 1.17 0.0364 206 5.5 2.1 73% 27%12% 1.15 0.0360 212 5.4 2.2 71% 29%13% 1.14 0.0356 218 5.3 2.4 69% 31%14% 1.13 0.0352 224 5.3 2.6 67% 33%15% 1.12 0.0348 230 5.2 2.8 65% 35%16% 1.10 0.0344 237 5.2 3.0 63% 37%17% 1.09 0.0340 243 5.1 3.2 62% 38%18% 1.08 0.0336 250 5.0 3.4 60% 40%19% 1.06 0.0332 257 5.0 3.5 58% 42%20% 1.05 0.0328 264 4.9 3.7 57% 43%

COAL GAS CONTENT.xls








TOTAL ADSORBED FREE GAS ADSORBED FREE GAS ADSORBED FREE GASCOAL COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS TOTALPOROSITY CONTENT CONTENT CONTENT CONTENT CONTENT GAS IN PLACE GAS IN PLACE GAS IN PLACE(%) (SCF/TON) (SCF/TON) (SCF/TON) (% SCF/TON) (% SCF/TON) (MMCF) (MMCF) (MMCF)

0% 150 150 0 100% 0% 214 0 2141% 155 150 5 97% 3% 212 7 2182% 159 150 9 94% 6% 210 13 2233% 164 150 14 91% 9% 207 20 2274% 169 150 19 89% 11% 205 26 2315% 174 150 24 86% 14% 203 33 2366% 179 150 29 84% 16% 201 39 2407% 184 150 34 81% 19% 199 46 2448% 190 150 40 79% 21% 197 52 2499% 195 150 45 77% 23% 195 59 253

10% 201 150 51 75% 25% 193 65 25811% 206 150 56 73% 27% 190 72 26212% 212 150 62 71% 29% 188 78 26613% 218 150 68 69% 31% 186 85 27114% 224 150 74 67% 33% 184 91 27515% 230 150 80 65% 35% 182 98 28016% 237 150 87 63% 37% 180 104 28417% 243 150 93 62% 38% 178 111 28818% 250 150 100 60% 40% 176 117 29319% 257 150 107 58% 42% 174 124 29720% 264 150 114 57% 43% 171 130 302

G (scf) = 1359.7 * A (acres) * T (ft) * DEN (gm/cc) * GC (scf/ton)G (scf) = 43,560 * A (acres) * T (ft) * POR (frac) * (1-Sw) * Bg (scf/res scf)




Assume only methane gas in porosityAssume Z factor is 1Assume hydrostatic gradient is 0.433 psi/footAssume geothermal gradient of 1 degree F/100 feetAssume mean surface temperature of 70 degrees FAdsorbed gas is gas in coalFree gas is gas in cleats, fractures or any pore spaceEnter shaded data






TONS OF TOTAL ADSORBED FREE GAS ADSORBED FREE GASCOAL COAL BULK COAL/ COAL GAS SCF OF GAS/ SCF OF GAS/ COAL GAS COAL GASPOROSITY DENSITY BULK RES CF CONTENT BULK RES CF BULK RES CF CONTENT CONTENT(%) (GMS/CC) (TONS/RES CF) (SCF/TON) (SCF/RES CF) (SCF/RES CF) (% GAS/RES CF) (% GAS/RES CF)

0% 1.31 0.0409 30 1.2 0.0 100% 0%1% 1.30 0.0405 35 1.2 0.2 87% 13%2% 1.28 0.0401 39 1.2 0.4 76% 24%3% 1.27 0.0397 44 1.2 0.6 68% 32%4% 1.26 0.0393 49 1.2 0.7 61% 39%5% 1.25 0.0389 54 1.2 0.9 56% 44%6% 1.23 0.0385 59 1.2 1.1 51% 49%7% 1.22 0.0381 64 1.1 1.3 47% 53%8% 1.21 0.0376 70 1.1 1.5 43% 57%9% 1.19 0.0372 75 1.1 1.7 40% 60%

10% 1.18 0.0368 81 1.1 1.9 37% 63%11% 1.17 0.0364 86 1.1 2.1 35% 65%12% 1.15 0.0360 92 1.1 2.2 33% 67%13% 1.14 0.0356 98 1.1 2.4 31% 69%14% 1.13 0.0352 104 1.1 2.6 29% 71%15% 1.12 0.0348 110 1.0 2.8 27% 73%16% 1.10 0.0344 117 1.0 3.0 26% 74%17% 1.09 0.0340 123 1.0 3.2 24% 76%18% 1.08 0.0336 130 1.0 3.4 23% 77%19% 1.06 0.0332 137 1.0 3.5 22% 78%20% 1.05 0.0328 144 1.0 3.7 21% 79%









TOTAL ADSORBED FREE GAS ADSORBED FREE GAS ADSORBED FREE GASCOAL COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS COAL GAS TOTALPOROSITY CONTENT CONTENT CONTENT CONTENT CONTENT GAS IN PLACE GAS IN PLACE GAS IN PLACE(%) (SCF/TON) (SCF/TON) (SCF/TON) (% SCF/TON) (% SCF/TON) (MMCF) (MMCF) (MMCF)

0% 30 30 0 100% 0% 43 0 431% 35 30 5 87% 13% 42 7 492% 39 30 9 76% 24% 42 13 553% 44 30 14 68% 32% 41 20 614% 49 30 19 61% 39% 41 26 675% 54 30 24 56% 44% 41 33 736% 59 30 29 51% 49% 40 39 797% 64 30 34 47% 53% 40 46 858% 70 30 40 43% 57% 39 52 919% 75 30 45 40% 60% 39 59 98

10% 81 30 51 37% 63% 39 65 10411% 86 30 56 35% 65% 38 72 11012% 92 30 62 33% 67% 38 78 11613% 98 30 68 31% 69% 37 85 12214% 104 30 74 29% 71% 37 91 12815% 110 30 80 27% 73% 36 98 13416% 117 30 87 26% 74% 36 104 14017% 123 30 93 24% 76% 36 111 14618% 130 30 100 23% 77% 35 117 15219% 137 30 107 22% 78% 35 124 15820% 144 30 114 21% 79% 34 130 164

G (scf) = 1359.7 * A (acres) * T (ft) * DEN (gm/cc) * GC (scf/ton)G (scf) = 43,560 * A (acres) * T (ft) * POR (frac) * (1-Sw) * Bg (scf/res scf)


AIR DRILLING EXAMPLE

AIR FROM AIR COMPRESSORAIR IN AT 1,440 SCFM

AIR AND METHANE GASMIXTURE

AIR OUT AT 1,440 SCFMMETHANE OUT AT ? SCFM

HOLE DIAMETERIS 8.5 INCHES

PENETRATION RATEIS 0.5 MINUTES/ FOOT

COAL DENSITYIS 1.4 GRAMS/CUBIC CENTIMETERS

ASSUMPTIONS

1) DRILLED COAL VOLUME AND DENSITY CAN BE DETERMINED2) NO FORMATION FLUIDS (GAS, OIL OR WATER) OR DRILLING FLUID FLOW BETWEEN WELLBORE AND FORMATION3) GAS ESCAPES CUTTINGS PRIOR TO MEASUREMENT4) THE GAS TRAP LIBERATES AND DECTECTORS MEASURE THE PERCENTAGE AND VOLUME OF GAS EXITING WELLBORE5) DRILLING FLUID DOESN'T INTERACT WITH HYDROCARBON GASES

OBJECTIVE

MEASURE THE GAS CONTENT OF DRILLED COALSAND REPORT AS STANDARD CUBIC FEET OF GAS PERTON OF COAL

AIR DRILLING EXAMPLEPAGE 1 OF 4

GAS DETECTOR MEASURESPERCENT OF METHANE IN AIR

(GAS 50 UNITS, 0.5%, 5,000 PPM OR 0.005 V/V)

DATA

1) HOLE DIAMETER (inches) (DIA = 8.5 in)2) PENETRATION RATE (minutes/ft) (PR = 0.5 min/ft)3) COAL DENSITY (grams/cubic centimeter) (DEN = 1.4 gms/cc)4) AIR COMPRESSOR INJECTION RATE (standard cubic feet per minute) (IR = 1,440 scf/min)5) GAS READING (units) (GR = 50 units)

FORMULANUMERATOR

DENOMINATORGAS CONTENT =

GAS (scf)

WEIGHT (tons)GAS CONTENT =

PROCEEDURECALCUALTE NUMERATOR

GAS (scf/min)

WEIGHT (tons/min)=

GAS VOLUME (scf) = 7.23

GAS VOLUME (scf) =(( 50 / 10,000 )

( 1 - ( 50 / 10,000 )1,440 )X

GAS VOLUME (scf) =INJECTION RATE (scf))X((GAS READING (units) / 10,000)

(1 - (GAS READING (units) / 10,000))

CANCEL min, CONVERT units TO V/V AND SOLVE FOR GAS VOLUME (scf)

GAS VOLUME (scf/min)GAS READING (units/min) =

100 UNITS = 1% METHANE IN AIR OR 10,000 PPM OR 1 MOLE % OR 0.01 METHANE VOLUME/TOTAL VOLUME(METHANE AND AIR)


GAS VOLUME (scf/min)+INJECTION RATE (scf/min)

DATA

1) HOLE DIAMETER (inches) (DIA = 8.5 in)2) PENETRATION RATE (minutes/ft) (PR = 0.5 min/ft)3) COAL DENSITY (grams/cubic centimeter) (DEN = 1.4 gms/cc)4) AIR COMPRESSOR INJECTION RATE (standard cubic feet per minute) (IR = 1,440 scf/min)5) GAS READING (units) (GR = 50 units)

FORMULANUMERATOR


GAS (scf)


PROCEEDURECALCUALTE DENOMINATOR

GAS (scf/min)

WEIGHT (tons/min)=

CALCULATE VOLUME DRILLED IN A MINUTE, CANCEL min

VOLUME OF COAL (cubic feet/minute) =

VOLUME OF COAL (cubic feet) = 0.5

= 0.78813

WEIGHT (tons)GAS VOLUME (scf)

GAS CONTENT (scf/tons) = =7.23 = 210

CONVERT VOLUME TO WEIGHT USING DENSITY

WEIGHT (tons) = 0.03121 X VOLUME OF COAL (cubic feet) X DENSITY (gms/cc)

WEIGHT (tons) = 0.03121 X 0.78813 X 1.4 = 0.0344

0.0344


0.00174 X PI X (DIAMETER (inches) ^ 2)

PENETRATION RATE (minutes/foot)

0.00174 X 3.14 X (8.5 ^ 2)

CORRECTIONS AND ADJUSTMENT1) USE CALIPER HOLE SIZE INSTEAD OF BIT DIAMETER (ASSUMPTION 1)2) USE COAL DENSITY FROM DENSITY LOGS, CORE ANALYSIS OR PUBLISHED MINE DATA, RATHER THAN DENSITY MEASURED FROM DRILL CUTTINGS (ASSUMPTION 1)3) SUBTRACT THE BACKGROUND GAS READING FROM THE GAS GAS READINGS MEASURED WHILE DRILLING THE COAL (ASSUMPTION 2)4) ADJUST GAS VOLUME FOR LARGE CUTTING HEIGHT (ASSUMPTION 3)

OPERATIONAL CONSIDERATIONS1) USE HIGH ROTARY TABLE SPEEDS, LOW WOB AND CONSTANT COMPRESSOR SPEED (RPM) (CONSTANT AIR OUTPUT)2) CONSIDER DRILLING A LARGE DIAMETER HOLE TO INCREASE GAS AND CUTTING VOLUME3) SWITCH TO MUD WHEN WATER FLOWS CAUSE HEADING FLOW4) DO NOT DRILL AFTER CONNECTIONS UNTIL THE HOLE IS UNLOADED, CIRCULATION IS ESTABLISHED AND AFTER CONNECTION GAS IS RECORDED ON THE MUD LOGGING UNIT

ADVANTAGES1) HIGH PERMEABILITY COALS FLOW2) WATER PRODUCTION WHILE DRILLING CAN BE MONITORED3) TOP SETS ARE FASTER DUE TO FAST CIRCULATION RATES4) COAL EASILY DISTINGUISHED FROM CARBONACEOUS SHALES5) OPERATIONALLY EASIER THAN MUD DRILLED HOLES TO MUDLOG

DISADVANTAGES1) COMPRESSOR EXPENSE ADDS TO DRILLING COSTS2) SURFACE CASING REQUIRED3) WATER DISPOSAL COST MAY BE HIGH4) WATER FLOWS MAY REQUIRE SWITCHING TO MUD5) IF WATER FLOWING HOLE MAY BECOME WASHED OUT6) ESTABLISHING CIRCULATION WITH MUD AFTER DRILLING TO FACILITATE LOGGING, RUNNING CASING AND CEMENTING MAY BE DIFFICULT7) DIFFICULT TO MUD LOG AFTER FIRST FLOWING COAL ENCOUNTERED8) LOW GAS READINGS IN GOOD COALS ARE MISINTERPRETED IF GAS READINGS IN MUD DRILLED HOLES ARE THE BENCHMARK9) NO EASY METHOD TO VERIFY INSTRUMENTATION IS FUNCTIONING IN NO OR VERY LOW GAS READINGS FORMATIONS


11/29/20017:20 AM

WSD

THIS TABLE IS USED TO DETERMINE GAS CONTENT (SCF/TON) IN AIR OR AIR/MIST DRILLED HOLESUSE ONLY FOR ACTUAL COMPRESSOR AIR RATE, BIT DIAMETER AND COAL DENSITY BELOWGAS UNITS ARE DEFINED AS 100 UNITS = 1% METHANE IN AIR

NOMIMAL COMPRESSOR RATING: 1800 SCF/MDERATION FACTOR: 20% PERCENT

ACTUAL COMPRESSOR AIR RATE: 1440 SCF/MBIT DIAMETER: 8.5 INCHES BIT AREA: 0.3941 FEET^2

COAL DENSITY: 1.4 GRAMS/CC COAL DENSITY: 0.0437 TONS/FEET^3

GASSHOW DRILL RATE (MINUTES/FOOT)(UNITS) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

10 8 17 25 33 42 50 59 67 75 84 92 100 109 117 12620 17 34 50 67 84 101 117 134 151 168 184 201 218 235 25130 25 50 75 101 126 151 176 201 226 252 277 302 327 352 37740 34 67 101 134 168 201 235 269 302 336 369 403 437 470 50450 42 84 126 168 210 252 294 336 378 420 462 504 546 588 63060 50 101 151 202 252 303 353 404 454 505 555 606 656 707 75770 59 118 177 236 295 354 413 472 531 589 648 707 766 825 88480 67 135 202 270 337 405 472 539 607 674 742 809 877 944 1,01290 76 152 228 304 380 456 532 608 683 759 835 911 987 1,063 1,139

100 84 169 253 338 422 507 591 676 760 845 929 1,014 1,098 1,183 1,267110 93 186 279 372 465 558 651 744 837 930 1,023 1,116 1,209 1,302 1,395120 102 203 305 406 508 609 711 813 914 1,016 1,117 1,219 1,320 1,422 1,523130 110 220 330 441 551 661 771 881 991 1,101 1,212 1,322 1,432 1,542 1,652140 119 237 356 475 594 712 831 950 1,069 1,187 1,306 1,425 1,544 1,662 1,781150 127 255 382 509 637 764 891 1,019 1,146 1,273 1,401 1,528 1,655 1,783 1,910160 136 272 408 544 680 816 952 1,088 1,224 1,360 1,496 1,632 1,768 1,904 2,040170 145 289 434 578 723 868 1,012 1,157 1,302 1,446 1,591 1,735 1,880 2,025 2,169180 153 307 460 613 766 920 1,073 1,226 1,380 1,533 1,686 1,839 1,993 2,146 2,299190 162 324 486 648 810 972 1,134 1,296 1,458 1,620 1,782 1,944 2,105 2,267 2,429200 171 341 512 683 853 1,024 1,195 1,365 1,536 1,707 1,877 2,048 2,219 2,389 2,560210 179 359 538 717 897 1,076 1,256 1,435 1,614 1,794 1,973 2,152 2,332 2,511 2,691220 188 376 564 752 941 1,129 1,317 1,505 1,693 1,881 2,069 2,257 2,445 2,633 2,822230 197 394 591 787 984 1,181 1,378 1,575 1,772 1,969 2,165 2,362 2,559 2,756 2,953240 206 411 617 823 1,028 1,234 1,439 1,645 1,851 2,056 2,262 2,468 2,673 2,879 3,084250 214 429 643 858 1,072 1,286 1,501 1,715 1,930 2,144 2,359 2,573 2,787 3,002 3,216

IF GAS CONTENT IS UNREASONABLY HIGH. MULTIPLY DRILLED (SCF/MIN) BY 1.44 TO DETERMINE GAS FLOW RATE IN MCF/DAY


MUD DRILLING EXAMPLEMUD DRILLING EXAMPLE

PAGE 1 OF 4

GAS DETECTOR MEASURESPERCENT OF METHANE IN AIR

(GAS 570 UNITS, 5.7%, 57,000 PPMOR 0.0570 V/V)

HOLE DIAMETERIS 8.5 INCHES

PENETRATION RATEIS 0.5 MINUTES/ FOOT

COAL DENSITYIS 1.4 GRAMS/CUBIC CENTIMETERS

CARBIDE LAG DATA1/2 CUP YIELDS 200 UNITSBASED ON CARBIDE LAGSIN CONNECTIONS BEFORE

AND AFTER COAL DRILLED

GAS TRAP

DRILLING MUD (WATER) PUMPEDDOWN AT 350 GALLONS PER MINUTES

ASSUMPTIONS

1) DRILLED COAL VOLUME AND DENSITY CAN BE DETERMINED2) NO FORMATION FLUIDS (GAS, OIL OR WATER) OR DRILLING MUD FLOW BETWEEN WELLBORE AND FORMATION3) GAS ESCAPES CUTTINGS PRIOR TO MEASUREMENT4) THE GAS TRAP LIBERATES AND DECTECTORS MEASURE THE PERCENTAGE AND VOLUME OF GAS EXITING WELLBORE5) DRILLING FLUID DOESN'T INTERACT WITH HYDROCARBON GASES

OBJECTIVE

MEASURE THE GAS CONTENT OF DRILLED COALSAND REPORT AS STANDARD CUBIC FEET OF GAS PERTON OF COAL

DATA

1) HOLE DIAMETER (inches) (DIA = 8.5 in)2) PENETRATION RATE (minutes/ft) (PR = 0.5 min/ft)3) COAL DENSITY (grams/cubic centimeter) (DEN = 1.4 gms/cc)4) CARBIDE LAG 0.5 cups YIELDS 200 unit RESPONSE 5) GAS READING (units) (GR = 570 units)

FORMULANUMERATOR


GAS (scf)


GAS (scf/min)

WEIGHT (tons/min)=

PROCEDURECALCULATE NUMERATOR

100 UNITS = 1% METHANE IN AIR OR 10,000 PPM OR 1 MOLE % OR 0.01 METHANE VOLUME/TOTAL VOLUME(METHANE AND AIR)

=units CH4scf CH4 1.269 scf C2H2

X200 units CH4

X1% CH4

100 units CH41% C2H2200 units CH4= 0.01268CF =

PRIOR TO DRILLING DETERMINE: 1) CALIBRATE THE MUD LOGGING UNITUSING METHANE (CH4) AND AIR MIXTURES, 2) DETERMINE THE RESPONSEOF MUD LOGGING UNIT TO ACETYLENE (C2H2), 3) DETERMINE THEAMOUNT OF ACETYLENE (C2H2) GENERATED BY 0.5 CUPS OF CALCIUMCARBIDE (CaC2) AND 4) DETERMINE THE CONVERSION FACTOR (CF)IN STANDARD CUBIC FEET OF METHANE PER UNIT OF GAS DETECTED1) 1.0% CH4 = 100 units2) 1.0% C2H2 = 200 units3) 0.5 CUPS CALCIUM CARBIDE (CaC2) = 1.268 scf OF C2H24) CALCULATE CONVERSION FACTOR (scf/unit)

AFTER COAL IS DRILLED CALCULATE THE AMOUNT OF GAS RELEASEDGAS VOLUME (scf) = GAS READING (units) X CF (scf/unit) = 570 X 0.01268 GAS VOLUME (scf) = 7.23

MUD DRILLING EXAMPLEPAGE 2 OF 4

DATA

1) HOLE DIAMETER (inches) (DIA = 8.5 in)2) PENETRATION RATE (minutes/ft) (PR = 0.5 min/ft)3) COAL DENSITY (grams/cubic centimeter) (DEN = 1.4 gms/cc)4) CARBIDE LAG 0.5 cups YIELDS 200 unit RESPONSE5) GAS READING (units) (GR = 570 units)

FORMULANUMERATOR


GAS (scf)


PROCEEDURECALCUALTE DENOMINATOR

GAS (scf/min)

WEIGHT (tons/min)=

CALCULATE VOLUME DRILLED IN A MINUTE, CANCEL min

VOLUME OF COAL (cubic feet/minute) =

VOLUME OF COAL (cubic feet) =

WEIGHT (tons)GAS VOLUME (scf)

GAS CONTENT (scf/tons) = =7.23 = 210

CONVERT VOLUME TO WEIGHT USING DENSITY

WEIGHT (tons) = 0.03121 X VOLUME OF COAL (cubic feet) X DENSITY (gms/cc)

WEIGHT (tons) = 0.03121 X 0.78813 X 1.4 = 0.0344

0.0344

MUD DRILLING EXAMPLEPAGE 3 OF 4

0.00174 X PI X (DIAMETER (inches) ^ 2)

PENETRATION RATE (minutes/foot)

0.5

0.00174 X 3.14 X (8.5 ^ 2)= 0.78813

OPERATIONAL CONSIDERATIONS1) USE HIGH ROTARY TABLE SPEEDS, LOW WOB AND CONSTANT MUD PUMP OUTPUT (SPM). DO NOT DRILL WITH KNOWN PROBLEMS2) USE WATER AS DRILLING FLUID AVOID POLYMERS AND HIGH VISCOSITY MUDS3) DO NOT DRILL WHILE MIXING MUD4) DO NOT DRILL WITH PARTIAL RETURNS, LOST CIRCULATION OR HIGH BACKGROUND GAS5) CIRCULATE BOTTOMS UP TO DETERMINE IF HIGH BACKGROUND GAS IS FROM FORMATION, GAS IN MUD OR ZERO SHIFT

MUD DRILLING EXAMPLEPAGE 4 OF 4CORRECTIONS AND ADJUSTMENT

1) USE CALIPER HOLE SIZE INSTEAD OF BIT DIAMETER (ASSUMPTION 1)2) USE COAL DENSITY FROM DENSITY LOGS, CORE ANALYSIS OR PUBLISHED MINE DATA, RATHER THAN DENSITY MEASURED FROM DRILL CUTTINGS (ASSUMPTION 1)3) SUBTRACT THE BACKGROUND GAS READING FROM THE GAS GAS READINGS MEASURED WHILE DRILLING THE COAL (ASSUMPTION 2)4) ADJUST GAS VOLUME FOR LARGE CUTTING HEIGHT (ASSUMPTION 3)5) NORMALIZE FOR MUD PUMP CIRCULATION RATE (ASSUMPTION 4)

ADVANTAGES1) LOW COST2) EQUIPMENT AND OPERATION FAMILIAR TO DRILLING CONTRACTORS3) CARBIDE LAGS VERIFY SYSTEM AND MUD LOGGING EQUIPMENT

DISADVANTAGES1) SLOWER DRILLING RATES2) LOST CIRCULATION MAY OCCUR3) WATER COSTS MAY BE HIGH4) MUD PUMPS MAY NOT BE SIZED FOR CBM DRILLING5) MUD PUMP OUTPUT MAY VARY DUE TO PLUGGED SUCTION LINES, WASHED OUT SEAT AND LINERS6) RAW GAS NUMBERS MAY BE MISLEADING7) NO INFORMATION ABOUT PERMEABILITY OR WATER IS GATHERED8) TOP SETS ARE SLOWER9) MORE CAVINGS AND WATER INTERACTS WITH CUTTINGS10) OPEN HOLE LOGGING TOOLS OFTEN DON'T GET TO BOTTOM11) OPERATIONALLY MORE DIFFICULT FOR MUD LOGGING

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