The traditional Eagle Ford Play extends northeast before encountering significant erosional thinning over the San Marcos Arch. On the eastern flank of the San Marcos Arch the Eagle Ford (defined in this paper as the interval from the Base of the Austin Chalk to the Top of the Buda Limestone) undergoes a facies change to the more clastic system of the Woodbine (Harris Delta). A discouraging exploration effort, east of the San Marcos Arch in the 2008 by a well-known exploration company, left the play untouched while the Traditional Eagle Ford Play exploded. However, significant shows in the Eagle Ford interval, east of the San Marcos Arch, ultimately led to a highly economic discovery of the Eagle Ford Shale in this newly emerging resource play spearheaded by Halcon Resources. Typical shale play parameter cut-offs were not effective in the discovery and delineation of the trend. However, the geologic and engineering components that define the economic limits of the play are typical:

  1. clay and calcite content and their effect on mechanical properties and recovery factor;

  2. source rock maturity and its effect on hydrocarbon type, reservoir energy, organic porosity and recovery factor;

  3. reservoir thickness and mechanical barriers as they are impacted by erosion; and

  4. bounding formations and the impacts of depletion. A significant database of core, wireline, mudlog, drilling, completion, microseismic and production data combined with an iterative integration of the data has led to a highly successful exploitation program. Significant efforts have been made to link drilling and completion efforts to the geologic and engineering model of the play and then iteratively compare production results back to the models. Key to this effort is to map recovery factor based on geologic and engineering information for input into recoverable hydrocarbon maps that can then be directly compared to lateral length adjusted EUR estimates from production. These maps, once calibrated, can then be used to show the economic extent of the play.

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