Evaluation and Simulation Study of Rock Drillability Grades in the Tazhong-Tabei Block

In response to the unclear rock properties of the formations in the Tazhong-Tabei block of the Tarim Basin and the difficulties in selecting drill bits, indoor rock drillability tests were conducted under high temperature and high-pressure conditions. The tests analyzed the changes in the drillability grade values of roller cone bits and PDC bits under the coupling effects of confining pressure and temperature. The research indicates that the drillability grade values of the rocks in this formation range between 4 and 6. Additionally, the drillability grade values of PDC bits are lower than those of roller cone bits. As confining pressure increases, the drillability grade values of the rocks also increase significantly when the confining pressure exceeds 30 MPa. Conversely, as the temperature rises, the drillability grade values of the rocks decrease substantially when the temperature exceeds 140 °C. A drillability analysis model for roller cone bits and PDC bits was established using finite element simulation software. The simulated drillability grade values of the rocks showed a discrepancy of less than 10% compared to the indoor test data, proving the accuracy and reliability of the indoor test data. Based on the rock drillability test results, the use of PDC bits is recommended for this formation. The optimized PDC bits successfully drilled through the target formation. These research findings are of guiding significance for accurately understanding the physical and mechanical properties of the formation rocks in the Tazhong-Tabei block and for the optimal selection of drill bits for this area.