FACTORS AFFECTING PLASTERING EFFECT IN CASING WHILE DRILINNG

Casing while Drilling is simultaneous process of drilling and running casing. One of the benefits using Casing while Drilling technology is plastering effect. Plastering effect or smearing effect is a process where cuttings and drilling mud are plaster to the borehole by force of casing due to small clearance between the annulus. This creates a thin mud cake that is less porous and less permeable, that helping to increase wellbore strength and reduce lost circulation during drilling. However, due to inconsistency of plastering effect during Casing while Drilling operation, it is hard to determine the factors that enhance plastering effect. The objective for this project is to determine the plastering effect factors using parametric studies. This project will focusing on vertical well and five drilling parameters. The parameters are casing size to wellbore size ratio, casing eccentricity, casing rotational speed, annular velocity and cutting volume fraction. For methodology, base case model is selected, such as the wellbore size of 0.4m and length of 4.2m. The simulation will be using two type of drilling fluid which is Newtonian and non-Newtonian fluid. Conclusion from the parametric study, in non-Newtonian fluid, the most contributing factors are cutting volume fraction, casing size to wellbore size ratio and casing rotational speed. While annular velocity and casing eccentricity does not contribute much. For Newtonian fluid, the most contributing factors are cutting volume fraction and casing size to open hole size ratio. While annular velocity, casing rotational speed and casing eccentricity still give lesser contribution in plastering effect. Comparing non-Newtonian and Newtonian fluid based on mud cake thickness and length, plastering effect are easily to produce in Newtonian fluid