ABSTRACT
A specialized borehole television system has been developed to aid in the development of gas production from eastern Devonian gas shales and other tight formations. The borehole television has advanced capabilities that are useful for visually diagnosing geological and reservoir factors associated with gas production. These features include high resolution color video, compass for orientation determination, control of borehole debris to maintain an unobstructed view, and simultaneous forward and upright side view. The side view is provided by positioning a mirror in front of the camera lens. Upright orientation of the side view image is maintained by rotating the camera and mirror assembly as a unit within the camera housing. The forward view provides rapid reconnaissance and the side view is used for detailed inspection of features in the borehole. A compass placed beneath the side view mirror is used to determine the orientation of the viewed image.
Field applications in the Appalachian basin demonstrated the usefulness of the color borehole television system. Geologists visually examined the depths of the gas wells to identify the factors affecting gas production. Of particular utility was the ability to definitively identify areas of gas and oil entry. Gas condensate was observed to bubble and vaporize as it entered the boreholes. The locations of side wall core samples were verified and the orientation of these samples was determined. Geological strata, crude oil stains, condensate and crude oil in the bottom of the well, cavities, porous zones, fractures, and casing were inspected. The camera was also used to locate a stuck logging probe lodged between the casing and a washout behind the casing The system has been installed in a borehole television logging truck for use in Gas Research Institute Devonian shale research programs and other commercial applications in the Appalachian Basin.
