Multicomponent
Seismic
Interpretation
and its Relation to Production Response in the
Leonardian Drinkard Formation of Vacuum Field, Lea County, New Mexico
RAINES, MICHAEL A., Kinder Morgan CO2 Co., L.P., Midland, Texas and TOM L. DAVIS, Colorado School of Mines, Golden Colorado
Vacuum Field sits along the margin of the Northwest Shelf of the
Permian Basin in central Lea County, New Mexico. Between 1995 and 1999, a portion of this
area was the study site for 3D/3C (multi-component) and 4D (time lapse) seismic
investigations concentrated on the San Andres Formation, and led by the Colorado School of
Mines’ Reservoir Characterization Project industry consortium (RCP). While RCP was
investigating the broader geological setting of the study area, certain
seismic
anomalies
became apparent in the Drinkard and Abo formations, especially in the shear-wave dataset.
Static reservoir characterization, using both shear and compressional
data
, was then
applied to Drinkard and Abo Formations. These investigations established an empirical
relationship between
seismic
response and production
data
. Further, the
seismic
and
production information can be explained by considering reservoir porosity development and
fracture distribution.
Abo deposition set the stage for future geometric relations with a sharply defined reef-enhanced shelf edge. During Drinkard deposition, relative sea level rise was slow enough to allow for shelf edge stabilization along the underlying reef trend. Laterally shifting, highly localized, and interfingering facies tracts (including patch reefs, which are now productive at Vacuum Field) were developed at this time. Today, enhanced matrix porosity associated with the patch reefs and fracture distribution (both open and healed) affect production characteristics in the field.
Production response was somewhat unclear until the data
was broken
into two categories: Instantaneous and Long Term. Initial Potential (IP) represented the
immediate deliverability of each well, and Average Production over the first six months
represented the long term storage space available to each well. Both datasets mapped
distinct (but different) patterns. Based on a loosely controlled geologic model
constructed from the limited core
data
available, long term production apparently
corresponds to patch reef areas, and higher IP areas correspond to regions of open or
partially open fracture sets.
Two seismic
datasets exhibited patterns very similar to the
production maps. Anisotropy analysis (a comparison of fast and slow shear wave
birefringence velocities) matched the IP distribution. A map of the ratio of compressional
velocity (VP) to fast shear wave velocity (VS1) gave a response similar to the average
production
data
map. The implication, then, was that VP/VS1 ratio mapping also revealed
higher porosity areas, and anisotropy analysis also highlighted regions of open fractures.
Multi-component static characterization can be a powerful tool, once
calibrated to the geology of a specific field. If this type of data
were available early
in the life of a field, an optimized recovery scheme could be developed, and a specific
development drilling plan could be implemented, saving hundreds of thousands of dollars
while optimizing field production.