Leak-off or fluid loss to the forma

Leak-off or fluid loss to the formation must be controlled not only to minimize the potential for stuck pipe and wellbore instability but also to minimize formation damage. Leak-off can be controlled by laying down a thin, impermeable filter cake or by relying on elevated Low-Shear-Rate Viscosity (LSRV). A thin, impermeable filter cake requires bridging solids and fluid-loss-control agents. These materials will increase the plastic viscosity of the fluid. A thin, impermeable filter cake can also create a dramatic pressure gradient across its thickness that may increase the potential for differentially sticking a non-rotating drillstring. By elevating the LSRV of the fluid, leak-off can be controlled without creating a dramatic pressure gradient across the formation face.