(19)
(11) EP 0 209 217 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
01.07.1987 Bulletin 1987/27

(43) Date of publication A2:
21.01.1987 Bulletin 1987/04

(21) Application number: 86303324

(22) Date of filing: 01.05.1986
(84) Designated Contracting States:
BE DE FR GB IT NL SE

(30) Priority: 14.05.1985 US 733723

(71) Applicants:
  • Cherrington, Martin D.
     ()
  • Cherrington, William D.
     ()

(72) Inventor:
  • Cherrington, Martin D.
     ()

   


(54) Apparatus and method for forming an enlarged underground arcuate bore and installing a conduit therein


(57)  An apparatus and method for drilling a pilot bore hole (B) along an underground arcuate path (P) between two surface locations (0, E). The pilot bore hole (B) is drilled in one direction with a drill string (10) having a leading pipe section (10A) of a reduced diameter to provide increased flexibility. Upon completion of the pilot bore hole (B), a reamer (48) connected to a product conduit (46) is connected to the drill string (10). Drill string (10) pulls the reamer (48) and product conduit (46) along the pilot bore hole (B) in an opposite direction for enlarging the bore hole (B) to receive the product conduit (46). A spud bit (34) has a flat or blunt leading end portion (34A) with a discharge opening (34D) therein to discharge high velocity drilling fluid into the formation at a location offset from the longitudinal axis of the drill string (10) to assist in guiding the drill string (10). An in-hole hydraulic motor (70) is provided in an embodiment (Fig. 7) for rotating the drill bit (78), and the longitudinal axis of a drive shaft (74) for the drill bit (78) is offset from the longitudinal axis of the drill pipe string (10) to assist in a deviation of the drill bit (78).







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