NS23A-1637
STATIC AND DYNAMIC RESERVOIR CHARACTERIZATION USING
HIGH RESOLUTION P-WAVE SEISMIC VELOCITY DATA IN DELHI FIELD, LA
Authors’ Emails:
sidra1982@gmail.com
tdavis@mines.edu
Sidra (Shahid) Hussain and Dr. Thomas Davis
Reservoir Characterization Project, Geophysics Department, Colorado School of Mines
Abstract
2. Static Characterization
Static and dynamic reservoir characterization was done on high resolution P-wave
seismic data in Delhi Field, LA to study the complex stratigraphy of the Holt-Bryant
sands and to delineate the CO2 flow path. The interpretation was done on bandwidthextended seismic data. Acoustic impedance inversion done on monitor and base
surveys helped in delineating CO2 flowpaths and the channel geometry in the
reservoir.
To monitor the flow of CO2 within Paluxy and Tuscaloosa sandstone formations, dynamic characterization was done using merged
2008-10 survey as the base survey and RCP (June 2010) survey as the monitor survey. The surveys were cross-equalized to
increase the repeatability. Model-based acoustic impedance (AI) inversion was performed on both the surveys to quantify the
changes in acoustic impedance with the addition of CO2 and water in the field. Fluid substitution modeling was done on well data
to model the expected changes in AI with CO2 and water.
Overlap
RCP
June 2010
Mar
2010
Acknowledgements
3.1 Cross-Equalization
2008
1. Introduction to Delhi Field
Permanent
Patch
(Jan 2010)
Survey Re-gridding
1 mile
Location of the seismic surveys in the field. The merged survey of 2008 and March
2010 was used as the base survey for 3D interpretation and the RCP survey from
June 2010 was used as the monitor survey for time-lapse interpretation in this study.
(Sun Oil Co. and Denbury Resources Inc.)
Static Time Shift
Time-Variant Time
Shift
Bandwidth extension was applied by Geotrace on the 3D seismic datasets using the
method of continuous wavelet transform to recover the lower and the higher
frequencies in the seismic bandwidth that were lost from earth’s reflectivity during
transmission. The method increased the dominant frequency in the data and
decreased the tuning effect.
After
Bandwidth
Extension
T= 20ms
T= 12ms
F=1/T=83.3 Hz
F=1/T=50Hz
Areal extent is 6200 acres
15 miles long
Delhi OOIP 357 MMBbls
RCP Study Area 7 sq miles
The steps taken to cross-equalize the base and the monitor surveys
2
2
0
Before Cross-equalization
After Cross-equalization
Positive Seismic Amplitude
NRMS maps and their respective histograms within the reservoir zone. The repeatability has improved with cross-equalization.
However, some zones of low repeatability around the wells are observed where one expects to see changes with production and
injection. The middle of the reservoir shows high repeatability. This could mean that the middle of the reservoir is being bypassed.
3.2 Model-based Acoustic
Impedance Inversion
Statistical constant phase wavelets extracted from the merged (2008-2010) survey
within 800-1100 ms, Inline=1019 and Xline=1001-1379
0
Positive Seismic Amplitude
3.3 Fluid Substitution Modeling
0
AI % change
-5
GR log
-10
5% CO2
-15
10% CO2
-20
-25
1400
Post-BE data
traces
overlain on
pre-BE data
After BE
Before BE
QC for Phase-shift: For most peaks and troughs, there is no phase shift.
Hierarchy of a model-based acoustic impedance
inversion (Modified from Young, 2006).
Location of Delhi Field in relation to the surrounding structural features
(Modified after Mancini, et al. 2008a).
MCF/D
BPD
100,000
BPD
QC for Time Shift: The time
difference falls within the range of -1
and +1 (see histogram) which is
normal for a trace by trace
computational continuous wavelet
transform process.
20,000
WATER
INJ
100,000Prior
1970
Production data not
available
Prior
1970
Primary
Production
RF ~14%
Secondary
Production
RF ~ 40%
Production
data not
available
Primary
Productio
n RF
~14%
OIL
PROD
Secondary
Production
RF ~ 40%
50
0 45
65
60
55
WATE
WATER
R INJ
PROD
OIL
Time in years
PROD
55
60
65
0
N
Injector Wells
Producer Wells
1 mile
2005
2400
Percentage change in acoustic
impedance with the addition of
CO2 under different pressure
conditions.
10% CO2
1600
1800
2000
Pressure (psi)
2200
2400
Percentage change in acoustic
impedance with the increase in
effective pressure for CO2
replacing brine.
4. Results
35
1 mile
GAS
PROD
1800
2000
2200
Pressure (psi)
5% CO2
N
GAS WATER
PROD PROD
Production history data of Delhi Field before the tertiary recovery started
0
(Modified from
Time in years
2005
45 Denbury Resources Inc.).
50
QC of well-to-seismic ties: Synthetic
seismograms (red) created using the
wavelets shown below the ties; The
correlation coefficient of pre-BE data is
94% while that of the post-BE data is
73% which is reasonable for a high
frequency data.
1600
8
7
6
5
4
3
2
1
0
1400
2.2 Structural Interpretation
MCF/
D20,00
0
AI% change with effective pressure for CO2
replacing brine
AI % change at different effective pressures
for CO2 replacing brine
2.1.1 QC of Bandwidth Extension
A generalized stratigraphic section of the Cretaceous formations in Delhi Field
(Denbury Resources Inc.).
Cross-Normalization
2.1 Bandwidth Extension
Before
Bandwidth
Extension
Location of Delhi Field (Evolution Petroleum Corporation).
Spectral Shaping
AI % change
I would like to thank Dr. Tom Davis and my thesis committee for helping me
with this research, Denbury Resources Inc. for sponsoring the research and
providing us with the data, Geotrace for doing the bandwidth extension and
Colorado School of Mines, Geophysics Department’s Reservoir
Characterization Project (RCP) for funding my research.
•
•
•
•
3. Dynamic Characterization
-25
Injector Wells
Producer Wells
Amplitude map of Paluxy from the
Amplitude map of the top of TUSC 7 from
the merged BE survey showing bright sandstonemerged BE survey showing SW-NE
trending meandering channel-like
bodies in red.
features in hot colors.
-4
An arbitrary dip line showing amplitude
difference through four of the wells in the
phase-1 injection pattern. The effect of CO2
can be seen around the injectors.
AI % difference map with a 2 ms window centered at
with the production data from June 2010 overlain; the
black dashed line is the oil-water contact; notice the
negative impedance change below the OWC. The
lighter yellow color shows area where Paluxy is not
being swept completely.
AI % difference map at TUSC 7 top; the white
triangles are TUSC 7 injectors and the white
circles are TUSC 7 producers; the black
polygons show the flow paths of CO2
illuminating channel-like features in the
sandstone.