首页|Evaluation of rock-bit interaction test under simulated ultra-deep well conditions based on similarity principle
Evaluation of rock-bit interaction test under simulated ultra-deep well conditions based on similarity principle
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NSTL
Elsevier
As the need for reaching fuel reserves at greater depths increases, scientists have been exploring and developing the technology required to efficiently drill rock at highly pressured environments over the past 30 years. However, there are still gaps in the understanding of the physical phenomena involved. One of the basic problems has to deal with is the rock-bit interaction during the rock breaking process. In order to evaluate the drilling efficiency and bit wear in ultra-deep formation, parameters of ultra-deep drilling simulator were calculated based on the similarity principle, followed by the design and manufacture of ultra-deep rock-bit interaction simulator. Considering the influence of formation differential stress change on bit footage, the effects of weight on bit (WOB) and rotary speed on torque, bit wear and rate of penetration (ROP) were studied firstly under the conditions of in-situ stress of 240 MPa and temperature of 200 degrees C. The results of similar simulation test show that under the conditions of in-situ stress of 240 MPa and temperature of 200 degrees C, WOB at 8.0-8.5 kN and rotary speed at 180-240 rad are the optimal drilling parameters. Correspondingly, the on-site WOB at 128-136 kN and rotary speed at 45-60 rad are the optimal mechanical parameters on the drilling site, which can lead to high cutting efficiency and low wear rate of the bit. The horizontal differential stress has a significant impact on the ROP. With the increase of the stress difference in the horizontal direction, the footage efficiency decreases obviously, and the decrease degree is about 87.5%. The test results will help optimize rock breaking tools and drilling parameters to improve rock breaking efficiency.
NSTL
Elsevier
