Hydrogeology of an Alpine Valley, southeastern Hydrogeology of an Alpine Valley, southeastern British Columbia British Columbia –– Implications for Coalbed Implications for Coalbed

Methane Exploration and Development Methane Exploration and Development

SHANE M. HARRISON , M.Sc., P. Geol., P. Geo.SH Consulting Services

APPROACH / OUTLINEAPPROACH / OUTLINE

PART I PART I –– OverviewOverview

nn Location / Physical SettingLocation / Physical Settingnn Stratigraphy / HydrostratigraphyStratigraphy / Hydrostratigraphynn Data CollectionData Collection

•• PressurePressure•• ““TransmissivityTransmissivity””

(permeability)(permeability)•• Water ChemistryWater Chemistry

nn Sampling Locations / Sampling Locations / Instrumentation Instrumentation

PART II PART II –– GROUNDWATER FLOWGROUNDWATER FLOW

nn Flow SystemFlow System–– Physical ConstraintsPhysical Constraints–– Hydrochemical ConstraintsHydrochemical Constraints

nn Numerical ModelingNumerical Modeling

PART III PART III –– Exploration / Production Exploration / Production ConsiderationsConsiderations

nn Production Production –– e.g. Well Spacing e.g. Well Spacing nn Gas Content / Gas originGas Content / Gas origin

APPROACH / OUTLINEAPPROACH / OUTLINE

PART I PART I –– OverviewOverview

nn Location / Physical SettingLocation / Physical Settingnn Stratigraphy / HydrostratigraphyStratigraphy / Hydrostratigraphynn Data CollectionData Collection

•• PressurePressure•• ““TransmissivityTransmissivity””

(permeability)(permeability)•• Water ChemistryWater Chemistry

nn Sampling Locations / Sampling Locations / Instrumentation Instrumentation

PART II PART II –– GROUNDWATER FLOWGROUNDWATER FLOW

nn Flow SystemFlow System–– Physical ConstraintsPhysical Constraints–– Hydrochemical ConstraintsHydrochemical Constraints

nn Numerical ModelingNumerical Modeling

PART III PART III –– Exploration / Production Exploration / Production ConsiderationsConsiderations

nn Production Production –– e.g. Well Spacing e.g. Well Spacing nn Gas Content / Gas originGas Content / Gas origin

GENERAL LOCATION MAPGENERAL LOCATION MAP

STUDYSTUDYLOCATIONLOCATION

COAL FIELDS COAL FIELDS LOCATION MAP LOCATION MAP

(general)(general)

Alberta Alberta ––British Columbia borderBritish Columbia border

PHYSICAL SETTINGPHYSICAL SETTING

nn ALPINE VALLEY, FRONT RANGES, ROCKY ALPINE VALLEY, FRONT RANGES, ROCKY MOUNTAINSMOUNTAINS

–– ELEVATIONSELEVATIONS•• LOWLAND (VALLEY) LOWLAND (VALLEY) -- 1550 1550 -- 1600 m1600 m•• UPLAND UPLAND -- 2200 2200 -- 2800 m2800 m

nn RUGGED TERRAIN WITH FEW DATARUGGED TERRAIN WITH FEW DATA

2200 - 2800 m asl1550 m asl

1600 m asl

Rocky Mountains Elk Valley

Approx. 6 km

Approx. 3-4 km

N

bridge

PHYSICAL / CHEMICAL PHYSICAL / CHEMICAL HYDROGEOLOGY HYDROGEOLOGY

nn STRATIGRAPHY DEFINES MAJOR STRATIGRAPHY DEFINES MAJOR HYDROSTRATIGRAPHIC UNITS:HYDROSTRATIGRAPHIC UNITS:

–– CARBONIFEROUSCARBONIFEROUS•• LIMESTONE;SOME DOLMITE AND SANDSTONELIMESTONE;SOME DOLMITE AND SANDSTONE

–– TRIASSICTRIASSIC•• SANDSTONE AND SHALESANDSTONE AND SHALE

–– JURASSICJURASSIC•• SHALE AND SANDSTONE/SILTSTONESHALE AND SANDSTONE/SILTSTONE

–– JURASSIC/CRETACEOUSJURASSIC/CRETACEOUS•• SANDSTONE , SILTSTONE, SHALES, COAL (Mist SANDSTONE , SILTSTONE, SHALES, COAL (Mist

Mountain Formation)Mountain Formation)•• Coals are subCoals are sub--bituminousbituminous

GEOLOGICALMAP

• Syncline

• Bourgeau Thrust

• Lewis Thrust

Bourgeau Thrust

Lewis Thrust

CROSS-SECTION

Syncline:

• Plunges north at shallow angle• Open to slightly overturned• Axial plane strikes at ≈160º; dips westerly

Groundwater Surface Water SamplingSamples collected of surface and formation water (groundwater) for chemical analyses from:• Seeps, streams, open wells, ponds, monitoring wells / piezometers

Hydraulic DataHydraulic conductivity and water level data from:• Open wells, monitoring wells / piezometers

Hydrological Data

• Gauging stations, streams, seeps, ponds

DATA COLLECTION

Site 1

Site 2

Elk RiverValley

open wells

streams

ponds

seeps

CBM test

guaging st.

Sample / Monitoring Locations(Plan View)

SAMPLINGSAMPLINGINSTRUMENTATION SITES 1 and 2INSTRUMENTATION SITES 1 and 2

(CROSS(CROSS--SECTION SITE 1)SECTION SITE 1)

VE = .65x

APPROACH / OUTLINEAPPROACH / OUTLINE

PART I PART I –– OverviewOverview

nn Location / Physical SettingLocation / Physical Settingnn Stratigraphy / HydrostratigraphyStratigraphy / Hydrostratigraphynn Data CollectionData Collection

•• PressurePressure•• ““TransmissivityTransmissivity””

(permeability)(permeability)•• Water ChemistryWater Chemistry

nn Sampling Locations / Sampling Locations / Instrumentation Instrumentation

PART II PART II –– GROUNDWATER FLOWGROUNDWATER FLOW

nn Flow SystemFlow System–– Physical ConstraintsPhysical Constraints–– Hydrochemical ConstraintsHydrochemical Constraints

nn Numerical ModelingNumerical Modeling

PART III PART III –– Exploration / Production Exploration / Production ConsiderationsConsiderations

nn Production Production –– e.g. Well Spacing e.g. Well Spacing nn Gas Content / Gas originGas Content / Gas origin

CONCEPTUAL MODEL OF FLOW CONCEPTUAL MODEL OF FLOW PHYSICAL HYDROGEOLOGYPHYSICAL HYDROGEOLOGY

M. King Hubbert (1940)

Classic Model Of Upland To Lowland Flow

Joseph Toth (1963)

Regional Flow Systems

UPLAND UPLAND –– LOWLAND FLOWLOWLAND FLOW

“ALTITUDE EFFECT”δ18O and δ2H (data from Yonge et al., 1989)

δ2H = -75.67 – 0.015 (elev.) – 0.08 (dist.)δ18O = -10.25 – 0.002 (elev.) – 0.009 (dist.)

““lighter or depletedlighter or depleted”” δδ 1818O / O / 22HH

Isotopic fractionationIsotopic fractionation

““heavyheavy”” isotopesisotopes

““enrichedenriched”” δδ 1818O / O / 22HH

HYDROCHEMISTRYHYDROCHEMISTRYCONSTRAINTS ON FLOWCONSTRAINTS ON FLOW

nn APPROXIMATELY 50 SAMPLES COLLECTED APPROXIMATELY 50 SAMPLES COLLECTED FROM:FROM:

–– MONITORING WELLSMONITORING WELLS•• COMPLETED FROM ABOUT 50 TO 200 m DEPTHCOMPLETED FROM ABOUT 50 TO 200 m DEPTH

–– OPEN WELLS (UP TO 600 m DEPTH)OPEN WELLS (UP TO 600 m DEPTH)–– SEEPSSEEPS–– PONDSPONDS–– STREAMSSTREAMS–– ELK RIVERELK RIVER

“ALTITUDE EFFECT” δ18O and δ2H

GROUNDWATER GROUPS GROUNDWATER GROUPS -- STUDY AREASTUDY AREA

TDS

SYNTHESISSYNTHESIS

nn GROUP A GROUNDWATER (GROUP A GROUNDWATER (““freshfresh””))•• HIGH TRITIUM; ENRICHED HIGH TRITIUM; ENRICHED δδ1818O/O/δδ22HH•• LOW TDSLOW TDS

–– LOW HCOLOW HCO33--

nn GROUP B GROUNDWATER (GROUP B GROUNDWATER (““evolvedevolved””))•• LOW OR NO TRITIUM; DEPLETED LOW OR NO TRITIUM; DEPLETED δδ1818O/O/δδ22HH•• HIGH TDSHIGH TDS

–– HIGH HCOHIGH HCO33-- ENRICHED IN ENRICHED IN δδ1313CC

nn INTERMEDIATEINTERMEDIATE–– TRANSITIONAL / MIXED COMPONENTTRANSITIONAL / MIXED COMPONENT

HYDROCHEMICAL CONSTRAINTS ON FLOWDepleted δ18O and δ2H

FLOW SYSTEM FLOW SYSTEM MATHEMATICAL REPRESENTATIONMATHEMATICAL REPRESENTATION

nn 33--D FINITE ELEMENT D FINITE ELEMENT –– Watflow 3Watflow 3--D (Molson et al.)D (Molson et al.)

nn BOUNDARY CONDITIONSBOUNDARY CONDITIONS•• Water table is fixed (specified head)Water table is fixed (specified head)•• Lewis and Bourgeau thrusts assumed Lewis and Bourgeau thrusts assumed

impermeable (no flow)impermeable (no flow)

nn SOLVE FOR STEADYSOLVE FOR STEADY--STATE FLOW:STATE FLOW:

0)()()( =++dzdhKz

dzd

dydhKy

dyd

dxdhKx

dxd

NUMERICAL SIMULATION

Hydraulic Parameters:

• equiv. porous media• K values • porosity values• anisotropy ratios

Model Domain:Heterogeneous and anisotropic conductivity field with 420,000 elements (3-D domain)

Boundary Conditions:

• specified head• “no flow”

RESULTS - NUMERICAL SIMULATION

SO WHAT IS THE SO WHAT IS THE APPLICATION!!!!APPLICATION!!!!

APPROACH / OUTLINEAPPROACH / OUTLINE

PART I PART I –– OverviewOverview

nn Location / Physical SettingLocation / Physical Settingnn Stratigraphy / HydrostratigraphyStratigraphy / Hydrostratigraphynn Data CollectionData Collection

–– PressurePressure–– ““TransmissivityTransmissivity”” (permeability)(permeability)–– Water ChemistryWater Chemistry

nn Sampling Locations / Sampling Locations / Instrumentation Instrumentation

PART II PART II –– GROUNDWATER FLOWGROUNDWATER FLOW

nn Flow SystemFlow System–– Physical ConstraintsPhysical Constraints–– Hydrochemical ConstraintsHydrochemical Constraints

nn Numerical ModelingNumerical Modeling

PART III PART III –– Exploration / Production Exploration / Production ConsiderationsConsiderations

nn Production Production –– e.g. Well Spacing e.g. Well Spacing nn Gas Content / Gas originGas Content / Gas origin

CBM PRODUCTION

nn DECREASE DECREASE RESERVOIR RESERVOIR PRESSURE (for an PRESSURE (for an underunder--saturated initial saturated initial condition)condition)

–– METHANE DESORBS METHANE DESORBS FROM THE COAL FROM THE COAL STRUCTURESTRUCTURE

–– WATER AND GAS FLOW WATER AND GAS FLOW TOWARD THE TOWARD THE PRODUCTION WELLPRODUCTION WELL

waterflow

water & dissolvedmethane

gas & waterflow

water and gas flowingwater flowing

DISTANCE FROM THE BOREHOLE

drawdownoriginal potentiometric surface

discharge

STAGE 1 STAGE 2

STAGE 3

PRESSURE

CBM PRODUCTIONCBM PRODUCTION

CBM / WATER PRODUCTIONCBM / WATER PRODUCTION

DEWATERING STABLEPRODUCTION

DECLININGPRODUCTION

METHANE

PROD.

TIME

WATER

3-D FLOWMODELING

CBM DEVELOPMENT

CBM DEVELOPMENTCBM DEVELOPMENTDepressurizationDepressurization

•How many wells?•Spacing?•How much water?

““BULKBULK--ROCKROCK”” RESPONSE TO RESPONSE TO DEPRESSURIZATIONDEPRESSURIZATION

““Real WorldReal World””

nn Borrow methods from the Water Well Borrow methods from the Water Well IndustryIndustry

Pumping Test: (65 mPumping Test: (65 m33/day for 15 days) /day for 15 days) –– drawdown is proportional to drawdown is proportional to ““QQ”” (pumping (pumping

rate)rate)–– drawdown is inversely proportional to drawdown is inversely proportional to

hydraulic conductivity (hydraulic conductivity (““KK”” or or ““TT””))

DRAWDOWNDRAWDOWN22,000 minutes (15 days) Q = 65 m22,000 minutes (15 days) Q = 65 m33/day/day

VE = .65x

DRAWDOWN SCHEMATICDRAWDOWN SCHEMATIC

Steep and narrow drawdown cone

1. steep and narrow→ low perm

2. volume of rock impacted by pressure-pulse is small

CBM EXPLORATION

Zone(s) of most significant overZone(s) of most significant over--pressuring?pressuring?

CBM EXPLORATION (con’t)

EFFECTS ON FLOW SYSTEM EFFECTS ON FLOW SYSTEM e.g. Water Table Fluxe.g. Water Table Flux

Other Data:

• Isotopic data• Stream flow• Monitoring well

Gas Origin???Gas Origin???

EXPLORATION: Biogenic ProcessesEXPLORATION: Biogenic Processes

EXPLORATION: Geochemical Markers EXPLORATION: Geochemical Markers

nn δδ1313C C –– DIC becomes enriched (+35 DIC becomes enriched (+35 ‰‰) ) nn DIC concentration (mg/L) increasesDIC concentration (mg/L) increasesnn Methane concentration (mg/L) increases Methane concentration (mg/L) increases

diagram shows as DIC diagram shows as DIC ↑↑ δδ1313CCDICDIC ↑↑ and CHand CH44 ↑↑

TYPICAL OF METHANOGENIC ENVIRONMENTS!!

DIC, METHANE, δ13CDICGROUP B

GROUP A

EFFECT ON MAJOR ION EFFECT ON MAJOR ION GROUNDWATER CHEMISTRYGROUNDWATER CHEMISTRY

Carbon dioxide is generated through methanogenesis dissociates into the groundwater resulting in high DIC concentrations (1250 + mg/L)

SUMMARY AND CONCLUSIONSSUMMARY AND CONCLUSIONS

nn Setting Setting Alpine valley southeastern British ColumbiaAlpine valley southeastern British Columbia

Relief: 1550 Relief: 1550 –– 2800 m2800 m

Structurally relatively complexStructurally relatively complex

nn DataDataCollected from wells, seeps, streams, pondsCollected from wells, seeps, streams, ponds

Detailed hydraulic, geochemistry and flow Detailed hydraulic, geochemistry and flow

SUMMARY AND CONCLUSIONSSUMMARY AND CONCLUSIONSconcon’’tt

nn Gas OriginGas OriginPredominantly biogenic (COPredominantly biogenic (CO22 reduction)reduction)Generated by active groundwater flowGenerated by active groundwater flow

nn Flow and Flow ModelingFlow and Flow ModelingConstrain flow chemically and physicallyConstrain flow chemically and physically

Represent flow mathematicallyRepresent flow mathematically

Simulations useful for early stage evaluations of Simulations useful for early stage evaluations of development / exploration scenarios (must development / exploration scenarios (must understand limitations of models)understand limitations of models)

THANK YOU!THANK YOU!