As wellbores continue to be drilled deeper and farther than ever before, the need for improved drilling fluid systems that optimize fluid performance in harsh and challenging environments is at its highest demand.
Invert emulsion fluids are frequently chosen due to their high performance and low risk in various applications. Invert fluids are a particularly good choice when dealing with extreme environments, such as those with surface temperatures as low as - 26C (-15F) or those wells having bottom hole temperatures in excess of 250C (485F). Invert fluids are typically the preferred choice over water-based alternatives in deepwater and extended reach wells because of their inherently better lubricity and improved wellbore stability. The most important component of the invert fluid is the surfactant package, which maintains the solids in an oil-wet state, assists in filtration control, and stabilizes the internal phase of the fluid.
The latest developments in surfactant chemistries designed for invert emulsion fluids has resulted in a significant improvement in the performance of these fluid systems. Newly developed systems allow for simplified engineering due to formulation flexibility across temperature and density, high internal phase ratios with low viscosity, emulsion stability at temperature extremes, and a greener chemical profile. Each of these has a positive effect on drilling economics, environmental compliance, logistics, and health and safety.
This paper will review the new surfactant technologies, describing both their advantages and drawbacks from the standpoints of drilling performance and applicability, showing example data leading to these conclusions. The authors will also review the recent field usage of the surfactants described.