Clay-free synthetic-based fluid results in zero barite sag

摘要

Issues raised by deepwater drilling and changing environmental regulations led to a closer examination of several seemingly essential additives for invert emulsion fluids. Since the introduction of invert emulsion fluids in the 1960s, oil-based fluids (OBFs) and synthetic-based fluids (SBFs) have been formulated with a similar group of components: base oil, organophilic clay and lignite, lime, CaCl_2 brine, and emulsifier. The family of invert emulsion fluids has remained closely related in mud properties and performance expectations. The invert emulsion fluids were developed to help maximize rates of penetration, increase lubricity in directional and horizontal wells, and minimize wellbore stability problems such as those caused by reactive shales. Until operators began drilling in deepwater locations, where the pore pressure/fracture gradient margin is often very narrow, the standard formulations provided satisfactory performance.