Utilization of Gyroscopic Compass with Borehole Television Camera in Devonian Shale Wells, Appalachian Basin
The color Borehole Television Camera has, in the three short years since its introduction in the Appalachian basin, become an extremely valuable tool in evaluating wells in Devonian shale. This has been due to the camera's ability to detect fracturing and small hydrocarbon entries that are below the resolution threshold of conventional geophysical logging.
This potential of the camera has been greatly enhanced by the addition of a gyroscopic compass to the basic tool. This compass gives the added value of orientation to observed phenomena in both open and cased holes.
In the open hole, the camera can be used to determine the orientation of fracturing. This feature is extremely important because fracture orientation can vary with depth, which may be the reason that some previously observed fractures make gas, whereas others within the same well bore do not. The productive fracture orientation can also be tied back to regional lineation studies.
Within the open hole, the gyroscope can also be used to orient sidewall coring operations so that cores can, in addition to regular analyses, be evaluated for directional properties, such as permeability and direction of the source beds.
Induced fractures, created by open-hole stress testing, can also be observed and their orientation determined.
Prior to the introduction of the gyroscope, oriented cased hole observations were impossible because of the inability of a regular compass to operate in a cased hole environment. With the addition of the gyro, perforation orientation has been possible. This has become important due to the observation that, in at least one area of the Appalachian basin, hydrocarbon production appears to be related to perforation orientation.
AAPG Search and Discovery Article #91031©1988 AAPG Eastern Section, Charleston, West Virginia, 13-16 September 1988.