Lateral Continuity of Eagle Ford Group Strata in Lozier Canyon and Antonio Creek Terrell County, Texas
Gardner, Rand; Wehner, Matthew; Pope, Micheal C.
The complete section of the Cenomanian-Turonian Eagle Ford Group is well-exposed in Lozier Canyon and Antonio Creek in Terrell County, Texas. Lozier Canyon contains superbly exposed complete Eagle Ford Group outcrops in near cliff exposures, whereas two miles to the east, Antonio Creek contains bedding plane exposures of virtually every resistant bed of the Eagle Ford Group. Together these two outcrops provide an unprecedented opportunity to study the sedimentology and horizontal continuity of individual beds of the Eagle Ford Group. This area is a natural laboratory to further understanding unconventional mudstone reservoirs here and may provide analogs for other unconventional mudstone reservoirs elsewhere. Using-high resolution GigaPan TM photomosaics, detailed measured sections, petrography, and paleocurrent data, we are documenting the horizontal variability of individual beds within the Eagle Ford Group on the scale of a horizontal well. The Eagle Ford Group of west Texas was previously divided into five facies based on lithologic, biostratigraphic, and geochemical data. Facies A consists of approximately 20 feet of rippled and cross-bedded foraminiferal packstone-grainstone interbedded with organic-rich laminated carbonate mudstone. Facies B contains approximately 70 feet of organic-rich laminated carbonate mudstone with pinch and swell foraminiferal packstone-grainstone beds and abundant bentonite beds. Facies C contains approximately 40 feet of weakly carbonate cemented mudstone and foraminiferal packstone-grainstone beds. Facies D contains approximately 20 feet of nodular skeletal wackestone-packstone interbedded with carbonate mudstone. Facies E contains approximately 20 feet of skeletal wackestone-packstone interbedded with carbonate mudstone. In Antonio Creek, lateral variation on the scale of a horizontal well is observable in Facies A and B. Facies A contains a zone of contorted beds that changes in thickness and degree of sediment deformation along the outcrop. Facies B contains foraminiferal ripple laminated packstone-grainstone beds that transition from tabular bedded to wavy bedding before pinching out completely or transitioning to lensoidal bedding. The equivalent strata of facies A is the primary reservoir target for Eagle Ford Group wells in the subsurface of south Texas and understanding how these facies change laterally has obvious implications for predicting subsurface reservoir character in producing areas.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013