| Two mechanistic models for predicting cuttings transport in highly inclined wellbores are presented. The first model, which is referred to as the one-dimensional mechanistic model, takes into account only the area average fluid velocity and cuttings concentration across an annular section. The effects of the fluid velocity and cuttings concentration profiles are considered by introducing a velocity coefficient. The second, which is referred to as the two-phase solid-liquid model, takes into account the fluid velocity and cuttings concentration profiles. Both models assume the two-phase liquid-solid flow is steady-state, fully developed and incompressible.;The one-dimensional model is a modified slurry transport model used for horizontal pipelines. The new extended model, which is based on the critical deposition velocity concept, applies to the cuttings transport problem in eccentric inclined annuli. It allows the prediction of the critical flow rate and cuttings bed height under various conditions of hole angle, hole size, drilling muds and drilling rate. Model predictions are compared to experimental data obtained from two different large scale flow loops. The results show that the proposed model is sufficiently accurate for practical applications, although improvements would be achieved by including the effect of liquid and solids velocity profiles and cuttings concentration distribution in the annular cross-section. This gave the motivation for developing a more sophisticated model.;The two-phase solid-liquid model is based on a simplified version of the two-fluid model applied to the system under consideration. In this approach, the solids phase is treated as a continuous phase. The simplification is performed by neglecting the inter-particle interaction. A numerical procedure is developed to solve for two-phase solid-liquid flow within the eccentric annulus. The results from the model indicate that the cuttings will migrate to the smaller gap. Predictions of flow rate and rate of penetration, that are required to keep the particles suspended, show good agreement with the experimental data. This model showed significant promise for predicting cuttings transport. |
