Looking for gas in
all the tight places
Tom Davis
Reservoir Characterization Project
Colorado School of Mines
Rulison Field
Location of Rulison Field
Rangley
Meeker
Mesaverde
Outcrop
Grand Valley
Rulison
Parachute
Grand
Junction
Modified from Johnson (1989)
Rifle
Glenwood Springs
Mamm
Creek
Mesaverde Tight Gas Sands
Piceance Basin Center Gas
Williams Fork Formation Schematic:
Basin Centered, Lenticular Gas Sand Accumulation
DeBeque
Wasatch
Gas Transition
Zone
(Currently not
Completed)
Grand Valley
Parachute
Rulison
Transition Zone
Gas Saturated
WILLIAMS
FORK
FORMATION
West
East
(Courtesy Williams)
CAMEO
MEMBER
Gas Bearing
Sequence
(1700’ - 2400’)
4-5 Fracs
20-30 Sands
Rulison Reservoir Properties
Av. drilling depth to top of Rollins
8500 ft
Av. thickness of gas saturated section 1700-2400ft
Pore pressure gradient
0.44-0.66 psi/ft
Log porosity
6-14 %
Frac gradient
0.6-0.9 psi/ft
Matrix permeability
0.1-2.0 microd
Effective permeability
10-50 microd
Reserves
135 BCF
Average EUR/well
1.65 BCF
Well spacing
10 acres
EUR vs. Net Pay
Poor Correlation of Net Pay to EUR
Courtesy of:
Fracture Significance
Production Decline Curve with Fracture Signature
105
•Fractures in a well tend to produce
first.
•Followed by reservoir matrix production.
Slope 1
MCF
Slope 2
104
Reservoir Matrix Dominated Production
Fracture Dominated Production
Jackson, 2007
103
1
2
3
Years
4
5
6
Natural fracture
detection technology can
impact development of
tight gas reservoirs more
than any other single
technology
Ostby, 2003
Economics
• Dual Perm, 2.1 Bcf/Well,
$1.10/Mcf profit at 5$/Mcf
• Single Perm, 1.4 Bcf/Well,
$ .05/Mcf profit at 5$/Mcf
Vello Kuuskraa, ARI, 2006
Drilling Program
3D
Survey
Outline
Drilling Program
2005 – ‘06 Wells
2006 – ‘07 Wells
Estimated Ultimate Recovery
0.00-0.50
0.50-1.00
1.00-1.50
1.50-2.00
2.00-2.50
> 2.50
EUR in BCF/well
Courtesy Williams
Production Co
Seismic Acquisition Grid
  Source Location
  Receiver Location
R94W
VSP Location
T
6
S
1 Mile
Seismic Acquisition Parameters
Type survey
Subsurface bin size
Number of receiver pts
Number of source pts
Receiver grid
4-D, 9-C (time-lapse)
55’ X 55’
1500
770
110’ inline, 330’ line space
Source grid
Instrumentation
Receiver array
Source array (P-wave)
110’ inline, 660’ line space
I/O VectorSeis® System IV
1, 3-C VectorSeis® SVSM
Vertical vibrator
Source array (S-wave)
Shear wave vibrator -Two
orthogonal horizontal
orientations
Seismic volumes in PP time
PP volume
S11 volume
PS1 volume
MSVRD
UMV
Cameo
Coal_D
Guliyev, 2006
Difference (03-96)
MVRD
UMV
Shale
Cameo
Davis et al, 2003
‘03 – ‘06 P-P Difference
Xequal
gate
225ms
16
RMS Ampl. of Diff. ’03-’06
11
Gas Migration- Rulison
Reservoir
Fracture zone
Cameo Coal
overpressure
Davis, 2004
Fast vs. Slow Shear Waves
• Fast – S1
– rotated to be
parallel to faults &
fractures
• Slow – S2
– rotated to be
perpendicular to
faults & fractures
(Martin & Davis, 1987)
Resistive fractures for 3 study wells
Matesic, 2007
Time-variant Time Shifting
Original Data
S1
Shifted Data
S2
S1: Original
S2: Shifted
Transform Software’s TerraMorphTM
Volume Registration and Warper
Impedance Anisotropy
A
A
Anisotropy Log Well Intersection
UMV
B
Cameo
LaBarre 2007
B
Converted Wave Splitting
Araman 2009
Subsurface Feature Identification
S
Two-way Time (ms)
N
25
RMS Amplitude Map at Reservoir Interval
(Depth: 6000-6200 ft)
500 ft
Mazumdar 2009
Where to drill next?
Upper Mid-Reservoir
EUR in BCF/well
1.00-1.50
1.50-2.00
2.00-2.50
> 2.50
From LaBarre, 2007
Integrated Interpretation: Time-lapse results
Slow VP/VS relative (%) difference 2003-2006 @6200 ft
15%
0%
Meza, 2008
-15%
EUR and Faults
Well EUR (BCF): 0.00-0.50
Well EUR (BCF): 0.50-1.00
Well EUR (BCF): 1.00-1.50
Well EUR (BCF): 1.50-2.00
Well EUR (BCF): 2.00-2.50
Well EUR (BCF): 2.50-10.00
Faults From LaBarre,
2006; EUR from
Williams, 2003
Diagenetic Influences on Seismic Attributes
Vp/Vs and Clay Content
1.9
1.85
1.8
Vp/Vs
1.75
1.7
1.65
1.6
1.55
1.5
0
0.5
1
1.5
2
2.5
3
3.5
Increasing
Clay
Volume
Clay content
4
Stroker 2008
4.5
5
Vp/Vs1 Volume Section
Vp/Vs
2.23
1.58
Guliyev, 20066) /Vs log overlay
VP/VS Ratio – Bottom UMV Shale
VP/VS Ratio
- 2.0
- 1.9
- 1.8
- 1.7
- 1.6
- 1.5
From Araman 2009
- 1.4
Expected Ultimate Recovery
Economics
Drill the best wells first: 5$/mcf x 1
bcf incremental EUR = 5 million
dollars/well
Reduce fracing cost fracing into
depleted zones: 200,000$/frac
stage, saving 2 frac stages/well =
400,000$/well
30% incremental recovery:
(recompletions) =.6 bcf x 5$/ MCF =
3 million dollars/well
Conclusions
• The best fairway for
production at Rulison Field
is associated with tectonic
fracturing
• Fractured sandstone
geobodies can be detected
with shear wave seismic
data
Conclusions
• Time – lapse shear wave
seismic data can detect
pressure depleted zones
• Dynamic reservoir
characterization can
increase recovery in tight
gas reservoirs
Take Away Message
IT PAYS TO LOOK IN TIGHT PLACES!
With the right tools.
Acknowledgements
Adnoc, Anadarko, BG –Group, BP, CGGVeritas,
Chaparral, Chesapeake, Sinopec,
ConocoPhillips, Dawson, Denbury, Devon, ENI,
ExxonMobil, Fairfield, Fugro, Fusion,
Geokinetics, Hi-Point, IHS, ION, iReservoir,
Kuwait Oil Company, Landmark, Noble, OXY,
OYO Geospace, Paradigm, Paragon, Petrobras,
Polish Res. Inst., RepsolYPF, Reservoir
Imaging, RWE, Schlumberger, SMT, Shell,
Talisman, Total, Triangle, Transform, Tundra,
Whiting, Williams & Vecta Oil and Gas