Experimental investigation and CFD simulation of multiphase flow behavior in air reverse circulation drilling

In reverse circulation (RC) down-the-hole hammer (DTH) drilling, hole cleaning has a great impact on reducing accidents and improving efficiency. There is a technical difficulty in RC drilling to select the minimum air influx while keeping cuttings discharged smoothly according to different water invasion conditions. A novel experimental device was used to study the physics of multiphase flow associated with the cleaning process. Air influx required for cuttings transport was measured under different conditions in Rate of Penetration (ROP), cuttings diameter, and water yield, and influence among three factors were revealed. Furthermore, the computational fluid dynamic (CFD) method simulated and analyzed multiphase flow behavior. The results show that factors of ROP, cuttings diameter, and water yield obviously impact minimum air influx during the cuttings transport process. The accuracy and credibility of CFD method have been confirmed on account of reasonable agreement with experimental data (a relative error of less than 14% is achieved). The CFD simulation of multiphase transport reveals that cuttings velocity and pressure drop could be influenced by ROP, cuttings diameter, and water yield. Therefore, these factors should be carefully characterized during air RC drilling and hole cleaning to maximize the efficiency of cuttings transport.& COPY; 2023 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.

Automated summary

Hole cleaning is crucial for reducing accidents and improving efficiency in reverse circulation (RC) down-the-hole hammer (DTH) drilling. A novel experimental device was used to study the physics of multiphase flow associated with the cleaning process, and the computational fluid dynamic (CFD) method simulated and analyzed multiphase flow behavior. The results reveal that factors such as Rate of Penetration (ROP), cuttings diameter, and water yield significantly impact the minimum air influx required for cuttings transport.