Experimental Study and Modeling of Cuttings Transport Using Foam With Drillpipe Rotation

Although rotary drilling is being used in most wells, the impact of drillpipe rotation on hole cleaning during foam drilling has not been investigated. There has been no single predictive tool developed to address pipe rotation effects on foam drilling. This paper presents the first study of cuttings transport using foam with pipe rotation under simulated downhole conditions. A field-scale, high-pressure/high-temperature wellbore simulator with a 73-ft-long, 5.76x3.5-in. eccentric annular test section was used to investigate the effects of pipe rotation, foam quality and velocity, downhole pressure and temperature on cuttings transport, and pressure losses in a horizontal wellbore. Experiments were conducted with backpressures from 100 to 400 psi and temperatures from 80 to 160 degrees F. Pipe rotary speeds were varied from 0 to 120 RPM, with foam qualities ranging from 60 to 90% and foam velocities from 2 to 5 ft/sec. It was found that pipe rotation not only significantly decreases cuttings concentration in a horizontal annulus but also results in a considerable reduction in frictional pressure loss. The reduction in cuttings concentration is up to 40% at a medium foam velocity (3 ft/sec) when pipe is rotated up to 120 RPM. The decrease in frictional pressure loss is up to 50% at a medium foam velocity and is more than 60% at a low velocity. Using a higher foam velocity or quality also improves hole cleaning; however, pressure losses are significantly increased. 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, foam qualities, and velocities under different pressure and temperature conditions. Comparisons between model predictions and experimental results show that the difference is less than 15% in most of the cases.