State-of-the-art cuttings transport with aerated liquid and foam in complex structure wells

Both aerated liquid and foam drilling as underbanlanced drilling candidates have obtained the rapid development to better protect the reservoir. Due to the presence of highly-deviated and horizontal section of complex structure wells, if the fluid velocity is lower than a critical value in annulus, cuttings will accumulate and eventually develop cuttings bed, and may result in severe problems such as stuck pipe, higher torque and drag, and poor cementing quality. Here, the sensitive analyses, empirical correlations and mechanical models for cuttings transport with aerated liquid and foam were reviewed. Studies indicate that cutting parameters, fluid parameters, operational parameters and formation parameters have effects on cuttings transport, and fluid flow rate and rheology are mainly controlled parameters. Models for aerated liquid include particle movement model, maximum cuttings volume model, optimal gas and liquid flow rate model. Models for foam include vertical-section model, two-layer model, three-layer model, three-segments model and critical velocity model. We suggest that the future researches will mainly focus on comprehensive experiments with advanced flow loops, flow simulations, mechanical models, hole-cleaning techniques and hole-cleaning optimizing system.