An experiment testing In-situ combustion with oxygen as an enhanced oil recovery process was run at the Holt Sand Unit in Montague County, Texas, from 1981 to 1983. This report integrates the interpretation of geological and geophysical data collected by the Exploration and Production Research Department of ARCO Oil and Gas Company during the experiment. The report Illustrates monitoring of the burn in time using 3-D seismic data and describes the factors in the detailed geology of the reservoir which controlled the propagation of the burn.
The most important feature of a reservoir involved in a flooding type recovery program is formation permeability. The Holt Sandstone was found to contain a complex array of vertical and horizontal barriers and enhancements to permeability. The reservoir complexity required that a proper description of permeability include not only measured permeabilities from core samples, but also a detailed study of the depositionai history and post-deposltional alteration. The original permeability of the Holt, which was controlled by depositionai processes, has been overprinted by natural flushing, secondary cementation, and fracturing. A geologic model of reservoir-scale permeability is shown to be useful in interpreting the details of the combustion process.