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The AAPG/Datapages Combined Publications Database

Houston Geological Society Bulletin

Abstract


Houston Geological Society Bulletin, Volume 50, No. 5, January 2008. Page17 - 17

Abstract: Discovery and Development of the Lower Wilcox Southwest Speaks Field, Lavaca County, Texas

Frank G. Cornish and Robert W. Parker
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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