Paul Denney 11-15-2008 Presentation

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

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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

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Preliminary Structure Map: Top Trinidad Sandstone

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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

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Problems Encountered

Fugitive Gas

Poison Canyon gas and chemical contaminations are

now known to be derived from Vermejo-Raton coal

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1

2Evidence cited in WSP-1805 provesconductivity exists across dikes

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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.

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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

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Alluvial aquifer

Raton-Vermejo

outcrop

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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

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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

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2

See Water Supply Paper 1805, pg 83

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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

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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

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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.

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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

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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

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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

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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

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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

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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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Documents

Paul Denney 11-15-2008 Presentation