This work reports a test of empirical equations for the relationship of mechanical specific energy (MSE) and rate of penetration (ROP) with key drilling parameters including both weight on bit (WOB) and rotation rate of the drill bit per minute (RPM). The test of the above empirical equations was performed using a new set of experimental data from drilling Carthage Mable with a TerraTek drilling simulator. The data covers the variation in the values of WOB, RPM, hydraulic power, type of oilbased drilling fluids, and type of drill bit. Combinations of WOB and RPM values are determined within the experimental range that yields the highest ROP while using the lowest MSE. While showing the potential benefit of drilling parameter optimization, the results are encouraging when compared to what was achieved in drilling experiments with operating parameters that were not optimized.


Industry is significantly interested in improved drilling efficiency and reducing cost. This is particularly true when the exploration for oil and gas moves to greater depths and harsher environments. With support from U.S. Department of Energy, TerraTek (now part of Schlumberger) conducted a research project to investigate the effect of drilling parameters on drilling efficiency [1~3]. The research was conducted with the use of a TerraTek deepwell drilling simulator and a Wellbore Simulator. Variables examined included drill bit types, drilling fluid types on selected drilling parameters, weight on bit (WOB), and rotation rate of the bit (RPM).

The drilling optimization study was continued at the National Energy Technology Laboratory (NETL) with focus on the effect of both WOB and RPM, since these two parameters are frequently adjusted while drilling. A set of empirical relationships was developed based on the experimental data from drilling Crab Orchard Sandstone [4,5]. A model appeared to indicate that such an optimized condition did exist, giving rise to a higher rate of penetration (ROP) with less use of mechanical specific energy (MSE) where MSE is the energy spent on removing a unit volume of rock mass while drilling. This work further tested the above mode for drilling Carthage Mable, which is another type of rock that is frequently encountered while drilling though hard formations. Polycrystalline Diamond Compact (PDC) bit and oil based mud are used for the test as a representative of deep drilling conditions

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