A Study of Factors Influencing the Drillability of Shales: Single-Cutter Experiments With STRATAPAX^(T) Drill Blanks

Single-cutter experiments using STRATAPAX drill blanks have been conducted to evaluate the effects of shale properties, drilling fluid pressures, and cutter configurations on the drillability of shales. Shale properties were determined by triaxial compression tests and adsorption isotherm testing. The cutting action of various cutter shapes was first studied using plasticine clay and lead models at atmospheric conditions and then using shale samples subjected to drilling fluid pressure. Shale samples were translated horizontally past the cutter which was restricted so it could move only in the vertical direction. Rock position, tool displacement and three components of force on the cutters were recorded simultaneously. Results of these tests are expected to provide data needed to aid in the design of bits containing STRATAPAX drill blanks for more effective drilling in shales.