TX 75083-3836, U.S.A., fax 01-972-952-9435.Bridging agents are used in Drill-In fluids to prevent problems of massive loss circulation to the formation and formation damage through fine solids migration that invade the hydraulic flow channels of the reservoir rock. Also, thick cake build up that induces a differential sticking problem, as well as torque and drag of the drill string are avoided. The first step when selecting the particle size distribution of bridging agents (specifically CaCO 3 ) in Drill-In fluids is the petrophysical characterization and pore geometry determination of the rock. In consolidated sands, the criterion of selection of particle size of bridging agents is: 1/7 D pore throat

TX 75083-3836, U.S.A., fax 01-972-952-9435.