Experimental and CFD analyses of cuttings transport in horizontal annuli and a study on isotropic rocks for strength correlations

The research activities performed in this study focused on the cuttings transport process in horizontal annuli that represents the horizontal drilling phenomenon. Both experimental and numerical approaches have been adopted to investigate the efficient hole cleaning process. Numerous flow conditions were examined in laboratory conditions and the subsequent visualization was performed with the help of a high-speed camera. The effects of drilling parameters such as drill pipe’s rotational speed (RPM), eccentricity and flow rate were scrutinized throughout the experimental and computational fluid dynamics (CFD) analyses. The common findings indicate enhanced hole cleaning ability at increased RPM and eccentricity. On the other hand, an increasing trend for pressure drop across the annulus section is identified with the enhanced drill pipe’s rotation (RPM), eccentricity and flow rate. The last part of this study examined tensile and shear fracture examination to find out different strengths of isotropic rock samples and establish strength correlations among them. This study will contribute to an ongoing investigation to predict cuttings size distribution from rock formation properties and drilling parameters. Unconfined compressive strength and indirect tensile strength (UCS-ITS) and unconfined compressive strength and point load strength index (UCS-PLSI) correlations were developed. Additionally, the ultrasonic pulse wave measurement was performed to establish the unconfined compressive strength and primary wave velocity (UCS-VP) relationships for sandstone and medium strength rock like material (RLM). Ultimately, all fitted relationships were analyzed through a comparative study with published correlations. This study on isotropic rocks is a part of an investigation to predict cuttings size distribution and future research will take the lead from this current thesis