مدل هیدرولیک سه بخشی برای قلمه حلقوی حمل و نقل با فوم در حفاری افقی

Through mechanical analysis, an improved hydraulic model for annular cuttings transport with foam was established for horizontal drilling. Based on the two critical inclination angles, the entire well was divided into three segments. The Bagnold stress, generalized power law rheological model and modified hindered particle settling velocity in foam fluid were adopted in the model to improve the simulation accuracy. The proposed model allows more precise prediction of cuttings transport property in the whole range of well inclination angle. Model performance was examined via case study and experimental data. Simulation results given by the propulsion iteration and trial-and-error method agree well with in-situ horizontal well drilling practice for the case study, and the comparison between the model prediction and Capo's experimental data shows satisfactory agreement.

In the interest of lower exploratory development cost and higher oil recovery ratio in current petroleum industry, the underbalanced horizontal drilling (UBD) technology has been developing as one of the highlights in international petroleum drilling market. As a special form of UBD, foamed drilling shows pronounced advantages in the improvement of hole cleaning efficiency, hydrocarbon reservoir acquisition and protection, increase in penetration rate and reduction in drilling cost. Hence, it has been extensively applied throughout the world. The cuttings transport performance with foam drilling fluid, however, has been less described because of the complexity of multiphase flow. Most of present related publications slight the difference of cuttingstransport at different inclination angles when over-pursuing relatively simplified models adoptable for much longer well section. For instance, the two-layer mechanical models established by Martins[1], Doan[2] and Li[3] cannot describe the cuttings transport property at relatively higher inclination angles when moving bed and stationary bed exist simultaneously, and the three-layer mechanical models presented by Nguyen[4]

1) A three-segment hydraulic model for cuttings transport with foam has been established. The horizontal section is simulated by an improved three-layer model, consisting of suspension layer, moving layer and stationary bed. The transitional section is studied by a two-layer model considering the sliding phenomenon of cuttings bed. The vertical section is assumed to be a homogeneous suspension. The proposed model can more accurately reveal the annular cuttings transport performance within the whole range of inclination angle in horizontal and highly-inclined wells. (2) Simulation results for the case study show a good agreement with the drilling practice in oil field. The smaller error between simulated results and experimental data verifies the rationality of model assumptions and the feasibility of research method. The research is helpful for in-good understanding of multi-phase flow behavior of foam fluid in horizontal well annuli. It provides basic guide for in-situ horizontal well drilling design and operations.