Abstract: A drill pipe/casing protector assembly for an underground drilling system comprises a well bore in an underground formation, a fixed tubular casing installed in the well bore, a rotary drill pipe extending through the casing and having an O.D. spaced from an I.D. of the casing (or well bore) during normal drilling operations, and a protective sleeve mounted around the drill pipe and spaced from the I.D. of the casing, and upper and lower thrust bearings affixed to the drill pipe above and below the sleeve to retain the sleeve in a fixed axial position on the drill pipe. The sleeve contacts the I.D. of the casing when the drill pipe deflects off-center to protect the casing from contact with the drill pipe or its tool joints during rotation of the drill pipe. Axial grooves in an I.D. wall of the sleeve allow fluid under pressure to circulate through a space formed between the I.D. of the sleeve and the O.D. of the drill pipe. Generally flat bearing surface regions on the I.D.

Abstract: A tubing friction reducer is mounted on a length of tubing within a bore hole. The friction reducer includes a cylindrical body having a first section and a second section hingedly secured around an exterior surface of the coiled tubing, the cylindrical body having an outside diameter larger than an outside diameter of the coiled tubing and less than an inside diameter of an adjacent bore surface. A plurality of roller bearings positioned on and extending outwardly from the cylindrical body extending in a generally axial direction along the cylindrical body for the purpose of reducing friction between the coiled tubing and the bore surface generated upon contact between the coiled tubing and the bore surface. Retaining mechanisms such as collapsible springs are included for securing the roller bearings to the cylindrical body. The tubing friction reducers are placed along the tubing at intervals to either minimize injector force, prevent buckling, and tubing failure, due to buckling or wear.