Modeling PDC cutter rock interaction

Optimizing the drilling performance in high pressure high temperature (HPHT) operations is crucial to successful, economic mineral extraction, and is one of the major goals behind the Department of Energy\u27s (DOE) Deep Trek program and the primary goal of the Ultra-Deep Drilling Simulator (UDS) laboratory currently being designed and constructed at National Energy Technology Laboratory (DOE-NETL).;To best leverage the valuable unique data from experiments in the UDS, a three-dimensional FLAC model of a single cutter interacting with the rock specimen (as tested in the UDS) has been developed. This cutter-rock model was developed using parameters so that various aspects of the model could be easily changed in subsequent runs.;This study will present the development of the cutter-rock model and the results of the initial numerical tests investigating the effect of various geologic and drilling parameters such as: rock strength, pore pressure, stress fields and cutting depth. Also, the results of the comparison/calibration of the model with single cutter laboratory tests will be presented.;Three basic initial models were run. First, two different rock types (a sandstone and a shale) with three different cutting depths are modeled to investigate the effect of rock strength and cutting depth on cutter loads. Second, The effect of various confining stress levels on the single cutter tests are analyzed by applying three different hydrostatic confinements (0 MPa, 25 MPa, and 50 MPa) to the core. Third, to incorporate the effects of fluid (both drilling mud and internal fluid) on the drilling process, pore pressure is included in the cutter/rock model. Results of these models showed that initial cutter/rock model is working properly.;The calibration of the 3D numerical model with the laboratory single cutter tests was primarily accomplished by matching the average vertical and horizontal loads on the cutter between the model and the laboratory tests. A FLAC 3D model was developed to back analyze the linear cutter test data published by Glowka (1989). The model eventually calculated the cutter loads pretty close to the test results. It is found that the different failure modes in the cutter/rock model, shear (crushing) and tensile (chipping), are highly dependent on the depth of cut and the tensile strength of the rock and greatly affect the cutting loads

New Abutment Angle Concept for Underground Coal Mining

In the Analysis of Retreat Mining Pillar Stability (ARMPS), Analysis of Longwall Pillar Stability (ALPS) and LaModel programs, the magnitude of the abutment loading adjacent to a gob area is calculated using an abutment angle concept, and the extent of the abutment loading is determined as solely a function of depth from an empirically derived equation. However, the latest in-situ stress measurements of abutment loading performed in the United States and Australia have shown that there can be significant deviations in the measured abutment magnitude and extent as compared to the predicted values from the empirical formulas used in ARMPS, ALPS and LaModel.;In this dissertation, stress measurements from U.S. and Australian mines were back analyzed by using analytical and numerical methods to investigate the measured abutment extent and loading. Ultimately, it was determined that the original empirical abutment extent formula in conjunction with the original ALPS square-decay stress distribution function was supported by the case histories reviewed in this dissertation. Also, for depths less than 900 ft, the average 21° abutment angle was supported by the case histories; however, at depths greater than 900 ft, the abutment angle was found to be significantly less than 21° and should be calculated with a new proposed equation