| While foam is gaining increasing applications in both drilling and cementing, understanding of how cuttings are transported during foam drilling is very limited. There has been no study on either foam drilling hydraulics or cuttings transport using foam with pipe rotation, though rotary drilling is the most widely used drilling technique. This study was undertaken to identify the effect of pipe rotation on cuttings concentration, pressure losses and velocity profile during foam drilling in a horizontal well under simulated downhole conditions. Both experimental and theoretical studies were performed.; A flow-through rotational viscometer, Foam Generator Viscometer (FGV), was used to investigate the rheology of aqueous and polymeric foams under pressures from 25 to 400 psi. The Dynamic Testing Facility (DTF) was used to study the effect of pipe rotation on foam flow with pipe rotary speeds ranging from 0 to 400 RPM. Cuttings transport experiments with pipe rotation were conducted on the Advanced Cuttings Transport Facility (ACTF), a full-size flow loop with a 73-ft long, 5.76" by 3.5" eccentric annular test section. Pipe rotary speeds were varied from 0 to 120 RPM, foam qualities from 60% to 90%, foam velocities from 2 to 5 ft/s, backpressures from 100 to 400 psi and temperatures from 80 to 160°F. Computational Fluid Dynamics simulations were performed to compare with experimental results.; Pipe rotation has a strong impact on cuttings concentration and pressure losses, depending on foam quality and velocity. Pressure exhibits a limited effect while a higher temperature slightly increases cuttings concentration and noticeably reduces pressure losses.; A mechanistic model and an associated computer simulator were developed for practical design and field applications. It can be used to predict cuttings concentration, bed height and pressure drop during horizontal foam drilling with various pipe rotary speeds, eccentricities, and foam qualities and velocities under different pressure and temperature conditions. Comparisons were performed between simulator predictions and experimental results from this study and previous investigations. The error of prediction is mostly within 15%. |
