Patent ID: 6250405
Filing Date: 2001-06-26
Classification: E21B

Abstract:
An underground drilling system comprising:a wellbore in an underground formation;a fixed tubular casing installed in the wellbore;a rotary drill pipe extending through the casing and having O.D. spaced from an I.D. of the casing or wellbore during normal drilling operations;a protective sleeve mounted around the drill pipe and spaced from the I.D. of the casing or bore for preferentially contacting the I.D. of the casing or bore when the drill pipe deflects off-center in the casing or bore to protect the casing or bore from contact with the drill pipe or its tool joints during rotation of the drill pipe;thrust bearing collars rigidly affixed to the drill pipe above and below the sleeve for maintaining the sleeve in a fixed axially position on the drill pipe;the protective sleeve mounted to the drill pipe via an internal sleeve I.D. configuration that substantially reduces the rotational rate of the sleeve upon frictional contact of the sleeve with the I.D. of the casing or bore, while allowing the rotary drill pipe to continue rotating within the sleeve at a rotation rate sufficient to conduct drilling operations in the formation;said internal configuration comprising longitudinally extending and circumferentially spaced apart axial grooves formed in an I.D. wall of the sleeve for allowing fluid to circulate through a space formed between the I.d. of the sleeve and the O.D. of the drill pipe;a diffuser region having at least one diffuser exit port for allowing fluid under pressure to exit through the space formed between the I.D. of the sleeve and the O.D. of the drill pipe to lift the sleeve off the casing.