What to do about deviation when rotating drill bits and drill pipe
Due to the viscous effect, the rotating braze rod bits force the mud to rotate, and the deviation effect occurs when the braze rods rotate eccentrically in the well, where the eccentric geometry affects the pressure loss in the annulus, and the annulus pressure is more important in fine hole drilling than in conventional drilling. Finely ground materials are ideally suited for fine-hole operations, where high rotational speeds are used in fine-hole continuous coring and drilling operations, where conventional weighted materials can be deposited on the inner wall of the brazing rod, leading to problems with wireline retrieval cores.
Barite is suitable for use in cationic brine muds and will not interfere with wireline core retrieval within a reasonable working range of drilling parameters. In fine bore wells, where well control can be a problem due to small annular gaps, well control is maintained by dynamic well control methods or heavy fluids, and conventional barite can form deposits or bridges. Pigment-grade barite is available through certain industrial solids suppliers and, while slightly more costly than conventional barite, is used in very small quantities and there is virtually no mud loss in fine-hole wells.
Pigment-grade barite can be formulated with a low viscosity mud that is acceptable in fine-hole drilling and is very fine and easily transported in the annulus. Because the particles are so small, this barite does not readily settle out of thin muds, and loss of finely ground barite is reduced by lowering the rotational speed. Pigment-grade barite can be mixed into the mud system using hoppers and standard mixing procedures. High-angle drilling reduces drilling costs by using smaller rigs, smaller casing sizes and minimizing drilling waste.
Conventional drilling rigs operate with wet-connected steerable tool systems and modified power swivel assemblies with tool cables that can be run through the system. Drilling from the surface to the intermediate casing point using a small rig, small rigs can drill faster and handle small tubing in horizontal sections more easily than a workover rig, which has recently become more popular with small diameter braze rod tools being used instead.