Pressure Profile in Annulus: Solids Play a Significant Role

Abstract

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.

Overview Solids Transport Study and Application in Oil-Gas Industry-Theoretical Work

“…The layer models were initially developed for slurry transport (Wilson 1970and 1976, Doron 1986). Later the model was adapted to solids transport studies for oil industry applications (Gavignet et al 1989, Martins 1990, Santana et al 1998, Nguyen et al 1998, Martins et al 1999a, 1999b, Kamp et al 1999, Cho 2001, Ramadan 2001, Doan et al 2003, Li 2004, Okunsebor 2006, Naganawa et al 2006, Cheng et al 2008, Costa et al 2008, Lu 2008, Wang 2008, Huo 2009, Gau et al 2010, Zhang 2010, Chen 2011, Liu 2011and Zhang et al 2014.…”

“…Some of the key parameters involved in the modeling require fine tuning in order to obtain acceptable prediction accuracy. In the following section, a brief review of layer modeling is discussed based on selected key papers in the literature (Naganawa et al 2006, Costa et al, 2008, Kamp et al, 1999, Cho, 2001, Gau et al 2010and Zhang et al 2014.…”

“…A few researchers (Cho 2001, Cheng et al 2008and Zhang et al 2014) developed the segmented layer models at sections of different deviation angle, namely at the highly deviated wellbore (60 deg to 90 deg), transient section (30 deg to 60 deg) and the near vertical section (0 deg to 30 deg). At each segment, different governing equations (the continuity equations and the momentum equations) and the related closure equations were constructed.…”

“…At each segment, different governing equations (the continuity equations and the momentum equations) and the related closure equations were constructed. A detailed discussion related to the segmented layer model can be found in Cho (2001), Cheng et al (2008) and Zhang et al (2014). As with other mechanistic models, there are a few model parameters that have been used to fit segmented layer model predictions to the experimental data.…”

Overview of Solids Transport Studies and Applications in Oil and Gas Industry - Experimental Work (Russian)

“…6, Zhang et al (2014) наблюдали типы формирования песчаного слоя в полностью эксцентричном кольцевом пространстве при различных углах наклона. Как показано на Рис.…”