In drilling operations, accurate estimation of pressure profile in the wellbore is essential to achieve better bottom hole pressure control. Adjusting the drilling fluid properties and optimizing flow rate require precise knowledge of the pressure profile in the circulation system. Annular pressure profile calculations must consider solids present in the drilling fluid because the solids drilled from formations may have a significant effect on pressure in the wellbore. In cases of high solids fraction or solid pack off, the pressure loss caused by solids is much higher than the friction pressure loss. This paper looks into the effect of solids on the wellbore pressure profile under different conditions. An extensive number of experiments were conducted on a 90-ft-long, 4.5″x8″ full-scale flow loop to simulate field conditions. The effects of solids on pressure profile in the annulus are investigated. In the experimental results, a significant difference is found between the pressure profile with solids and without solids in the wellbore. A practical approach to calculate the pressure profile by considering the effects of solids in the wellbore is developed. This approach is based on the results of solids behavior in the wellbore. Both solids fraction in the well and solids pack off are considered in the proposed approach. The prediction results are in good agreement with the experimental data.
The results of this study show how the pressure profile in the wellbore varies when solids present in the annulus. The pressure gradient with solids can be several times larger than the pure friction loss without solids. A decrease in flow rate may lead to a higher pressure profile and the risk of solids pack off in the wellbore because it increases the solids fraction. Results of this paper may have important applications in drilling operations.
