Oil-Based Foam and Proper Underbalanced-Drilling Practices Improve Drilling Efficiency in a Deep Gulf Coast Well

A recyclable oil-based foam drilling fluid (OBFDF) system has been developed to expand the benefits of controlled pressure drilling with foam onto water sensitive formations. This paper describes chemical development and presents drilling results for a Gulf Coast well drilled with the oil-based foam system. Not only did results confirm the ability of the foam system to control fluid loss and preserve formation permeability, but also, show the advantages of drilling with foam. Furthermore, a bit trip was saved drilling the reservoir in a single bit run, with a high rate of penetration and reduced gas inflow while drilling. The OBFDF is versatile, stable at high temperature (up to 450°F), compatible with H2S scavengers and reusable. Foam properties were successfully adjusted in presence of gas and condensate inflow. Still, the flexibility of foaming, defoaming and refoaming allowed surface separation and fluids reuse. Therefore, recycling liquid make up hydrocarbon reduced fluids and chemical usage with the associated cost reduction. Onsite modeling showed the controlled pressure contractor modeling software used for water-based foams can be adjusted to properly predict drilling parameters with oil-based foams.