Using Crosswell Seismic Tomography to Provide Better Reservoir
Resolution
in the
Wolfcamp Formation in Lea County, New Mexico
WELCH, CYNTHIA L., ROBERT L. MARTIN, and GREG D. HINTERLONG1, ChevronTexaco
Exploration & Production Company, 15 Smith Road, Midland, Texas 79705.
1Present address: Pure Resources, A Unocal Company, Midland, Texas
In the Vacuum Field located in Lea County, New Mexico, the Wolfcamp
Formation consists of alternating and intermingled layers of limestone, dolomite, and
shale. Located on the southeastern edge of the Northwest Shelf, the Wolfcamp was deposited
in a shallow shelf environment while experiencing considerable fluctuations in sea level.
The Wolfcamp appears to be laterally discontinuous based on log and 3D seismic data,
however individual reservoir-quality compartments are difficult to resolve with these
methods. Depositional models of carbonates in shelf environments indicate that units of
potential pay may not be laterally continuous; however they may be traceable if better
resolution
can be obtained regarding the depositional character of these units. In
addition, identifying shale units would greatly aid in determining the best path for
future horizontal wells in the Wolfcamp.
Crosswell Seismic Tomography was used to provide better reservoir
resolution
, which would lead to determining reservoir continuity, compartmentalization,
and characterization. After data collection, processing, and interpretation, a horizontal
well was drilled based on these results. The horizontal well targeted reservoir-quality
intervals that had not been identified in either log or 3D seismic analysis. The
horizontal well resulted in tests up to 121 BOPD, which was an increase of 91 BOPD from
original
vertical
well results. In addition to providing horizontal drilling locations in
the Wolfcamp, the crosswell seismic data has provided information essential to reservoir
characterization and our understanding of Wolfcamp deposition in this area. Based on the
crosswell seismic data, the Wolfcamp Formation does appear to be discontinuous with
several isolated reservoir-quality compartments present. Many of these reservoir-quality
compartments were not originally distinguished by either log or 3D seismic data. In
addition, this high
resolution
data has allowed us to compare the crosswell seismic
results with outcrop studies performed by the BEG near Van Horn, TX. Clinoforms have been
identified in the crosswell seismic data that appear highly similar to those seen in
outcrop near Van Horn, TX. Future application of this data exists in the merging of
crosswell seismic, 3D seismic, log data, and core data into one three dimensional model
that will provide us with a more complete understanding of the Wolfcamp Formation in the
Vacuum Field.