Hole stability issues and the need to reduced drillpipe torque have made oil-based drilling fluids the systems of choice for highly deviated or horizontal reservoir sections offshore Norway. However, the tendency of barite sag in non-aqueous drilling fluids has led to plugging of sand-control screens, thereby creating in some cases the need for a solids-free environment for the completion. Unfortunately, because of problems related to emulsion blocking when mixing filtrate from oil-based drilling fluid and water-based completion fluid, displacing to brine after drilling with oil-based fluid can damage productivity.
This paper describes the design and successful application of a unique high-density solids-free, oil-based completion fluid. This fluid obtains its density from an emulsified internal phase of heavy brine. This eliminates the requirements for solid weight materials for fluid density, providing a solids-free, oil-continuous environment for the completion.