How To Manage Drill-In Fluid Composition To Minimize Fluid Losses During Drilling Operations

Abstract

Summary Selection of the best drill-in fluid for drilling horizontal wells is essentially based on the characteristics of the filter cake formed in the near-wellbore region. Minimizing filtrate loss into the formation by forming a thin filter cake with low porosity and permeability is the key to managing formation damage problems. In this paper, the effects of drill-in fluid components and their interactions in the formation of a filter cake, which provides an effective caking process with reduced filtrate loss, have been evaluated. Statistically designed experiments carried out with a dynamic filter press apparatus were used to identify which variables had the most significant effect on filtrate loss and cake permeability so that the optimum fluid composition could be determined. These variables include the formation characteristics (permeability and pressure values) as well as the type and amount of the fluid components. Data obtained in this experimental design study were analyzed with the multiple-linear-regression method, which allowed us to model the filtrate loss and cake permeability. The analysis showed that the most important factors are the type and the concentration of the polymer. In particular, when the formation temperature is as high as 90°C, we can reduce the cake permeability and the filtrate loss by increasing the concentration of scleroglucan. An interaction effect between the concentration of scleroglucan and the more highly crosslinked starch was also identified, and none of the other variables showed any significant effects within the range of experimentation. This fact can be considered as an advantage because it allows flexibility in the choice of other factors when appropriate for the cost reduction.