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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Discovery and Development of the Lower Wilcox
Southwest Speaks Field, Lavaca County, Texas
Imagine Resources, LLC
The United Oil and Minerals #1 Pilgreen discovery in January
1996 opened up a significant Lower
Wilcox play throughout Lavaca and Colorado
counties, Texas. The play concept involved
finding undrilled Lower Wilcox structures
beneath Upper Wilcox dip-trending structural
axes. At the Southwest Speaks Prospect a large
shallow Upper Wilcox high-side fault
trap
had been drilled by three unsuccessful wells,
all of which had tested gas from different
Lower Wilcox sands. Adjacent downthrown
Lower Wilcox production was noncommercial,
and the primary target sands had never
produced anywhere in Lavaca or Colorado counties.
Production from Lower Wilcox sands at Southwest Speaks will
exceed 230 bcfg from 10 different sands. The main pays are in the
Roeder (a misnomer), Rainbow and Magnolia sands. The single
best well (Eaves #1) has produced 16 bcfg from the Rainbow,
which is the best zone with over 84 bcfg produced (10/2006). The
Rainbow Sand includes two upthrown fault
closures, the largest
of which covers 1490 acres and has over 515 feet of column.
The original prospect was developed on 2D data. Five wells were
drilled before 3D seismic over the field was completed in 1997.
The 3D showed the structural high was in an unexpected area.
The data was part vibroseis and part dynamite and acquired
at different times. Fault
shadows caused time sag and relative
amplitude problems.
All wells required fracture treatment and some had second fracs, which prolonged their life. Lower Wilcox gas has varying amounts of H2S and CO2 requiring treatment for sales. Generally speaking, the highest wells are the best producers, having the best porosity and permeability, but there are off-structure “sweet spots” in the Rainbow and Simpson sands.
Regional geology prior to 1995 showed a lack of production
along the Lower Wilcox Fault
Trend between
Dry Hollow Field and Provident City Field in
Lavaca County. At Southwest Speaks the best
production came from Lower Wilcox sands
that had not produced in the county.
Explorationists should always be looking for
new reservoirs and not be led only to those
prospects with nearby look-alikes in the same
target sands.
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