Application of reservoir characterization and advanced technology to improve recovery and economics to a low quality shallow shelf carbonate reservoir. Quarterly report, October 1, 1996--December 31, 1996 Page: 3 of 7
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Recent installation of a CO2 pipeline near the field allowed the phased development
of a miscible CO2 injection project at the South Welch Unit.
The reservoir quality at the West Welch Unit is poorer than other San Andres
reservoirs due to its relative position to sea level during deposition. Because of the
proximity of a CO2 source and the CO2 operating experience that would be available
from the South Welch Unit, West Welch Unit is an ideal location for demonstrating
methods for enhancing economics of IOR projects in lower quality SSC reservoirs.
This Class 2 project concentrates on the efficient design of a miscible CO2 project
based on detailed reservoir characterization from advanced petrophysics, 3-D seismic
interpretations and cross wellbore tomography interpretations.
During the quarter, simulation performance forecasts were made using the base
geologic model. The surface seismic and wellbore data were combined to develop an
improved geologic model for the simulator. Efforts to integrate the wellbore seismic
results into the reservoir characterization continue. Problems with the wellbore
seismic processing were traced to the processing software which is being corrected.
3-D SEISMIC INTEGRATION
The second stage of the geologic modeling required the integration of the 3-D
seismic data and the well data to capture the interwell porosity variations portrayed
by the seismic interpretations.
A methodology was developed to convert seismic attributes to log properties
of porosity and thickness x porosity (pore volume) within the San Andres reservoir
beneath the DOE demonstration area. This technique is discussed in detail in the
proceedings of a platform carbonate workshop' The vertical resolution of the 3-D
seismic within the San Andres reservoir was approximately 30 ft, which allowed the
two major depositional parasequences within the main pay - M1 to M3 and M3 to M5
to be identified (Fig. 1). Hence, it was possible to develop a seismic-derived map of
porosity and thickness x porosity for both intervals that represents the two
dimensional (x-y) distribution of the values averaged over the vertical interval. The
basic reservoir model represents the M1 - M3 interval with three layers and the M3 -
M5 interval with four layers. Therefore, the 3-D seismic vertical resolution is
inadequate to describe the model layering.
A methodology was developed to subdivide the seismic intervals to match the
model layering. At each wellbore control point, the model layers' percentage of the
total thickness and thickness x porosity was determined for both the M1 - M3 and M3
- M5 intervals. Percentage maps were constructed from this information which were
then integrated with the seismic maps to produce thickness and thickness x porosity
maps for each of the seven model layers between the M1 and M5 markers. ThisPage 2
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Application of reservoir characterization and advanced technology to improve recovery and economics to a low quality shallow shelf carbonate reservoir. Quarterly report, October 1, 1996--December 31, 1996, report, October 1, 1997; United States. (https://digital.library.unt.edu/ark:/67531/metadc695325/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.