Selection of the best Drill-in Fluid for drilling horizontal wells is based, essentially, on the characteristics of the filter cake formed 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 Fluids components and their interactions in the formation of a filter cake, which provides an effective caking process with reduced filtrate loss, have been evaluated. A statistically designed experiments carried out with a dynamic filterpress apparatus were used to identify which variables had the most significant effects on the 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 amounts of the fluid components.

Data obtained in this experimental design study were analyzed using the multiple linear regression method (MLR) which allowed us to model the filtrate loss and cake permeability. The analysis pointed out that the most important factor is the type and the amount of polymer concentration, particularly an increased concentration of scleroglucan improved the cake permeability and the filtrate loss. An interaction effect between the amount of scleroglucan and the more crosslinked starch was also identified. Besides the results indicated that the other variables did not have any significant effect within the range of experimentation. This fact can be considered as an advantage, as it allows flexibility for the choice of the other factors when deemed appropriate in order to cost reduction.

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