| 摘要 |
A tubular element (1) adapted for use downhole in drilling and oil & gas prospecting comprises a metallic mandrel (6) adapted to be connected (2,3) within a string of elongate elements, with a GRP(GFK) composite material (7) upon an outer surface of the mandrel in which a plurality of ceramic particles are partially embedded to present exposed contact surfaces in the formed composite material. The surface can be ribbed (4) with flow channels (5) therebetween. Suitable particles are of zirconium oxide, silicon nitride, cubic boron nitride, and mixtures of two or more thereof, whereby improvements in weight/strength ratio, fatigue endurance, increased torsional properties, with reduction of wear on the casing are obtained when such composite tubulars of the invention are used as drill pipe or work string sub-assembly elements. |
