An accurate characterization of natural fractures is an important part of reservoir exploitation in the gas-bearing Devonian shales of the Appalachian Basin. These reservoirs commonly have very low matrix permeabilities (10-9 to 10-7 md), and a well developed natural fracture system must be present to provide sufficient deliverability for economic production. A detailed fracture description is crucial to proper reservoir modeling and simulation.
Fractures have been identified and described in 440 feet of oriented whole core from two research wells in eastern Pike County, Kentucky. FMS, CAST, and Borehole Camera data have also been acquired, and the core data was used as a basis for the interpretation of these tools. Each tool has its own unique advantages and disadvantages, and guidelines have been established for the optimum use and interpretation of each.
The complex nature of the fracture systems in these reservoirs often pose special problems in fracture identification using these borehole imaging tools. The ability to properly characterize fractures in this reservoir is strongly influenced by the apparently very fine fracture apertures and limited fracture vertical extent.
Whole core represents the best source of data for a detailed, accurate fractured reservoir interpretation. The FMS and CAST are good fracture detection tools, but should be tied to whole core data. The borehole camera, though less quantitative than other tools, represents a reliable source of fracture data, and is inexpensive to acquire and interpret.