High Performance Water Based Drilling Fluids Design

With increasing wellbore complexity, drilling into more technically demanding areas, and increasing pressure to improve drilling economics, the drive to develop and utilize effective high performance water based drilling fluids has increased dramatically over the last few years. Drilling offshore in the lower Persian Gulf presents some unique challenges with many extended reach wells which encounter issues primarily related to wellbore stability through long, unstable shale formations, and high potential for down hole losses. The development of a water based drilling fluid that could effectively minimize operational problems while drilling these wells was a major challenge. Developing efficient treatments and engineering techniques tailored to the formation requirements have been equally as important. The net result of the correct application of these unique systems and additives has been to minimize the incidence of drilling induced lost circulation, to minimize fluid lost to formation, and to minimize drilling non productive time due to treatment of losses and managing wellbore instability. This paper describes the development and application of a uniquely engineered water-based drilling fluid that demonstrates enhanced shale stabilization properties, allowing water-based fluids to be used in applications previously reserved for invert emulsion systems. In addition the development and use of a new class of sealing additives is outlined, showing how further stabilization of the wellbore and minimization of losses can be accomplished. The authors will present laboratory test data on both the fluid system and sealing additives and performance data from the initial field trials