Coal Bed Methane Development (Tom Myers)

7/27/2019 Coal Bed Methane Development (Tom Myers)

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Coal Bed Methane

DevelopmentTom Myers, PhD

Hydrologic Consultant

Western Mining Action NetworkSept. 29-Oct. 1, 2005


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What is coal bed methane?

Standard natural gas:CH4Methane forms along

with coalIt is held in the cleatswith the coal

Substantial water

pressure needed tokeep methane in thecoal: 400 to 1000 ft ?


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Process of Developing CBM

Relieve pressure to

release methane by

removing water

Domestic wellscompleted in seams

produce methane due to

drawdown caused by

nearby pumping

6-7 times more natural

gas than in traditional

natural gas fields


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Set of wells in southeast MT


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What Happens to Developed

Water?

Most developed water is:

Discharged to surface water

Discharged to containment pond

Land applied for evaporation


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Discharge to Impoundment in Wyoming: Disposal

by evaporation, percolation or sometimes diverted

to LAD


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What are hydrologic impacts?

Groundwater depletion

Water table drawdown

Decreased flow to springs and streams

Groundwater Contamination

- Methane in the groundwater

- Seepage of disposed CBM water

Surface Water

- Water quality: Excess Sodium or Salt- Wasted water

- Changing channel shape


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How much water produced?

Gallons per minute/ WELL


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How much water?

In Montana

25000 wells in Powder River basin

Up to 9,000,000 acre-feet

No water right!

In Wyoming

Up to 50000 wells in PRB


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Effects of Withdrawing That Much Water

2003 Drawdown in Wyoming PRB

North to Left


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Lets look at more details

Hydrology of coal: effects of depletion

Quality of water being discharged: effects

on rivers/stream/plants.

Alternatives to wasting the water


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Montana Powder

River Basin

Many coal seams

down to 1800 feet

Coal seams

relatively small

proportion of total

thickness

Dietz up to 100 feet

thick


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Coal Seams as a Source

Coal seams a major source of water in the

PRB of Montana.

Thin conductive seams with low porosity

lead to a rapid expansion in the effects of

drawdown.


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Effects of CBM Pumping

Rapid

Drawdown.

Effect onadjacent

aquifer?

Well WRE-51 and 51A, 09S 40E S29

3200

3250

3300

3350

3400

3450

3500

3550

Aug-76 Aug-80 Aug-84 Aug-88 Aug-92 Aug-96 Aug-00 Aug-04

MSL(ft)

W R-51 W R-51A

Overburden


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Effects of Coal Mining

09S 40E S13

3280

3300

3320

3340

3360

3380

3400

3420

3440

3460

Dec-73 Dec-78 Nov-83 Nov-88 Nov-93 Nov-98 Nov-03

MSL(ft)

WRE-09, Screen 213-238 WRE-10, Screen 163-178 WRE-11, Screen 92-122


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Unaffected hydrology


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CBM effects on hydrology


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Coal Seams Next to Tongue River


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Effects of Discharge to Surface Water

Water Quality

Surface Water QualityEffects on Irrigation/Stockwater Usage

Changing Riparian Ecosystems to more

salt tolerant system


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Water

Chemistry

Horseshoe Canyon

Formation (Alberta,

Canada)Powder River Basin,

WY Piceance Basin,CO San Juan BasinCO, NM, AZ, UT Black Warrior Basin,ALMax

(mg/L)

min

(mg/L)

max

(mg/L)

Min

(mg/L)

Max

(mg/L)

Min

(mg/L)

Max

(mg/L)

min

(mg/L)

max

(mg/L)

min

(mg/L)

Na 861.0 112.0 800.0 110.00 2673. 1976. 5939. 3674. 3100. 570.0

Ca 128.00 2.70 69.00 5.90 1839.00 13.20 118.70 6.50 100.00 2.50

Mg 23.50 0.20 46.00 1.60 7.77 0.00 39.00 2.88 34.00 1.10

As 0.0022


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Recommend: Most Sustainable

Practice

Reinjection into aquifers depleted byCBM production.

Injection or percolation into depleted

aquifers with water treatment as requiredprotecting and/or enhancing waterquality.

Replace other uses where quality allows.Surface discharges with water treatment as requiredresulting in improved stream flows with adequatemitigations against negative impacts.


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Hydrology effects with Reinjection


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Coal Bed Methane Development (Tom Myers)