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8/3/2019 Paul Denney 11-15-2008 Presentation
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Possible Pathways of Vertical
Conductivity at thePetroglyph Little Creek
Coalbed Methane Project
Walsenburg, Colorado
Paul Denney, Consulting Geologist, Nov 2008
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Purpose of Study: Is VerticalConductivity Possible?
What is causing surface gas seeps, water welldepletion, chemical and methane contamination in
areas not observed before 2005?
Faults and permeable dikes may create verticalconduits explaining the problems listed above
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Gas fields require an overlying seal (usually thickshale) to prevent gas from raising vertically.
Geologic faults have broken the seals at the top of boththe Vermejo and Raton formations.
Evidence exists that prove the Unfug & Walsen dikesare not barriers to fluid flow.
Complex stratigraphy limits the use of pump tests todefine fluid flow.
Summary of Geologic Evidence
3
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Project Historydrilling began 1998water pumping began 1999to date 36,000 ac-ft water produced60 million cu-ft gas produced after largevolume pumps installed 2005
fugitive gas seeps and water wellcontamination noted 2005
4
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Preliminary Structure Map: Top Trinidad Sandstone
5
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Problems Encountered
Water Well Depletion-Excessive Water Production
Petroglyph is producing 5000X as much waterper million cu-ft gas as typical well in SpanishPeaks field
Is excess water coming from shallow aquifer?1. Petroglyph pump tests vs2. Peter Barkmann, Oct 2004, Vertical Hydraulic
Conductivity, Denver Basin; pump tests unreliable in
complex stratigraphy would not provide estimates
of vertical conductivity
6
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Problems Encountered
Fugitive Gas
Poison Canyon gas and chemical contaminations are
now known to be derived from Vermejo-Raton coal
7
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1
2Evidence cited in WSP-1805 provesconductivity exists across dikes
8
Statement by Norwest Quest Engineering toCOGCC Sept 25, 2008
Statement subject
to question
READ
READ
Geology and Hydrology
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The Reasoning Trap:
1Why is it important to recognize if thePoison Canyon is an unreliable aquifer?
2Why is it important to understand if dikesobstruct or facilitate subsurface fluidmovements?
If the statements on slide 8 are accepted at
face value, there is no reason to further
investigate dikes or the Poison Canyon aquiferas conduits of vertical fluid movement.
9
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Alluvium: unconsolidated sand, gravel andclay filling in todays stream valleys.
80% of the 495 permitted wells existing atthe end of 1965 were less then 100 deep.
Such shallow wells were probably inalluvium
10
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Alluvial aquifer
Raton-Vermejo
outcrop
11
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Page 35
Page 79
This slide a
composite of text
and diagram from:
McLaughlin, 1966
WSP 1805
As reported by Norwest-Quest
(Petroglyph sub-contractor): this
publication discussed the limitations ofthe Poison Canyon Formation as a water
source including the fact that yields from
the aquifer were small and the use of the
aquifer for water supply would be subject
to perennial water shortages (USGS,1966).
My findings: 1) After 4 readings I could
not find this statement or a similar one in
Paper 1805. The statement may (?) come
from a 1961 publication by same author.
1
East
Read
Dike
west
Alluvial aquifer
12
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Mapped on the surface May have undetected extensions in
subsurface Dikes extend deep into subsurface Must recognize the probability of
dikes as possible conduits
13
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2
See Water Supply Paper 1805, pg 83
14
DIKES
McLaughlin states: Both dikes and sills were intruded at high temperature
and altered the rocks through which molten material passed. Sandstone washardened and permeability reduced. Shale was also hardened, jointed and
permeability greatly enhanced. As a result, shale that usually has littlepermeability may be highly permeable adjacent to dikes and sills. Further;
altered zones of shale near dikes and sills can be conduits through which
water can move readily.
Norwest Quest Engineering, on behalf of Petroglyph submitted the following statement to
COGCC on Sept. 25, 2008
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Statement from McLaughlin, 1966 Water Supply Paper 1805, pages 36 & 37
Statement from Norwest-Quest Engineering, Sept 25, 2008 2
Little Creek
1930 1940 1949
15
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Pictou dike
Walsen dike
Unfug dike
The only methane seep found byApogee Surveys in 2001
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Well Logs: electrical & radioactiverecordings of interior walls of wellbores
Well Logs used to identify rock types Well logs used to correlate between wells Elevation of rock layers calculated and
structure (including faults) mapped
Surface observations can extrapolated intothe subsurface PPD Nov 08
17
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Raton Fm.
Vermejo Fm.
Wells logs are electrical and radioactivity recordings ofrocks penetrated by wells. They provide determination of
rock types and fluids in the wells.
18
Color key: yellow= sand; orange= siltstone usually,sometimes sand or conglomerate; green and gray= shale
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Petroglyph 35-11B Petroglyph 36-02 Basal Raton Conglomerate
Vermejo Fm.
Trinidad Ss
Petroglyph reports that Trinidad ss
and Vermejo have common
hydraulic conductivity. Thereforethis shale cannot be sealingNotice how this shale filled channel changes position
Sand channel changes position
Correlation
Between Wells
6500 feet apart
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Identify faults by comparing logs A fault is located by identifying intervals of
missing rocks
Faults move and offset rocks of differentage.
When permeable zones of differentformations are positioned together,conduits across stratigraphic zones arecreated and barriers are by-passed
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21
Trinidad
Sandstone
Detail
Structure
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Petroglyph 2W Petroglyph 3W Petroglyph 36-02
PPD Nov 08
Because of fault (missing
section), red zone now in
contact with yellow zone.
Hydraulic connection
established
22
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85 faulted
out; fault
cuts topRaton
Thick sandchannel changes
between wells.
Medium thicksand channel
changesposition in all 3
wells
PPD Nov 08
Barrett water well(offset 150N) total
depth 817
23
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Geologists must think in four dimensions. Sand bodies appearing in cross-sections as lenticular,
actually are channels extending back into the display
1. Channels run many miles, cross-cut other sand bodies2. Channels climb in the rock section
Gas migrates upwards along faults/fractures and laterally through cross-
cutting sand bodies.
Gas migrates through fractured dikesPPD Nov 08 24
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abandoned
meander: channelfilled with sand, later
buried by silt & mud
point bar: sanddeposits
new channel: mud buried by sandchannel
swamp area
Overbank depositsmuds, silts mixed
with minor sand
225As shown here a channel may run for many miles, yet width of channel
may only be mile across.
B
A
Walsenburg & Cuchara River; 65 million years ago,
perhaps 50 miles from the sea
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Cuchara River 65mya
Middle Raton Sandstone
paleoenvironment
Cuchara channel
Lathrop St PkIndex Map
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Coal in direct contact with down-cut
channel. Possible conduit for gas to move
vertically and along strike of channel
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28Little Creek CBM Project Water Production 1millionBW=129ac-ft
21.4MMBW
19.7
14.0
5.56.1
1.9
2.2
6.4
6.24.4
6.7 7.7
8.2
7.6 9.7
9.3
9.2
8.4
7.8
6.8
22.5
3.7
1.9
6.7
6.3
Dikes
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Six sidewall cores were
taken in igneous sill overan interval of 169.
Analysis showed reservoirquality rock saturated with
hydrocarbons. Formation
Imaging Log revealed 412open fractures over the
310 igneous interval.
Fractures have apertures0.8-2.0 millimeters.
Fractures may be due tocontraction during cooling
or later movement.
Beardmore
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Traditional seismic data provides informationon rock structure
Passive Seismic records microseismicity, ormovements within the earth. These occurnaturally or when in-situ stresses are disturbed
by fluid production.
1.
PS is recorded with geophones placed underground,2. PS can detect nearby faults, fluid anomalies and if
recorded over a period of time, fluid movement.
PPD Nov 08 31
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Traditional Reflection Seismic Data still used in
Oil & Gas Exploration.
Vertical scale shown here represents 4500
Horizontal scale = approximately 1 mile
Reflection events are generated at contrasting
rock strata contacts. Subsurface geologic
structure obvious.
This type data is a snapshot in time. Normally,little can be said about the fluids within these
rocks.
Fault
PPD Nov 08 32
Erosional unconformity
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Passive Seismic
Data
Trinidad, Colorado
2001
Seismic used todefine location and
attitude of
previouslyunknown fault
6000-20,000 belowthe surface..
Movement on this
fault occurred atdiscrete elevation
levels over the
monitoring period(5 weeks).
USGS OF-02-073 33
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Map view
Passive seismic cross-section views
1994 1999 2001 2002
34
Expanding gas
envelope
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Practical Use of
Passive Seismic
MonitoringAthabasca Tar
Sands,Alberta, Canada
Steam injected intolower portion of
well can be seento move towardright center of
display. Time lapse3 months. Change
in reflectivity is
caused bychanges in rock
density due toheating.
Base Survey Monitor survey +3 months
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Microseismic, Inc monitoring technique
Injection point
36
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Summary:
The problems; what affects water level in domestic wells?What causes the water contamination (methane and
chemical)?
The answer; pathways by which fluids move through thesubsurface
We have seen three types of conduits that may allow
contamination of the Poison Canyon aquifer by waters and
methane from the coaly formations. These are;
1. Previously undetected faults in the Petroglyph wells2. Leaky dikes in the immediate Little Creek area3. Sand channels cross-cutting other aquifers;What can be done to mitigate the problems?
1. Petroglyph is monitoring nearby water wells2. More emphasis on geologic study to identify additional faults
and possible downward-cutting sand channels
3. Passive Seismic monitoring 37
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Recommendation
Passive Seismic Monitoringis used to solveproblems like those facing Petroglyph Energy:
1) Is methane gas raising toward the surface
along faults or dikes;2) Are CBM wells lowering the water levels in
domestic wells;
3) Is Raton & Vermejo water mixing into the
Poison Canyon aquifer;
4) Are frac fluids escaping into the surroundingsediments?
Passive Seismic is a tool that shouldnt be
ignored and certainly it is to everyones benefit
to find answers to the above questions.
End of Program
PPD Nov 08
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END
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Late Cretaceous-Tertiary-
67-65 myaVermejo-Raton paleogeography
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Late CretaceousPaleoenvironmental
Map of North
American
Raton Basin
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Earliest Paleocene 65 mya Raton Formation paleogeography,Painting by Donna Braginetz, DMNS
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