GB971453A - Method of drilling an underwater well - Google Patents

Abstract

971,453. Boring earth &c. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Sept. 26, 1963 [Sept. 28, 1962], No. 37994/63. Heading E1F. A method of drilling an underwater well from a platform 11 comprises lowering a bit 32 on a drill string 21 into contact with the formation to be drilled, inserting into the drill string a reamer bit 36 of larger diameter than that of the bit 32 and spaced therefrom by a distance greater than the depth of water at the well location, drilling into the formation until the reamer bit has penetrated the formation sufficient to receive a well conductor pipe 35, raising the drill string to bring the reamer bit to the platform, removing the reamer bit from the drill string, and lowering the conductor pipe over the drill string into the hole 38 drilled by the reamer bit. To ensure that the drill string is not completely removed from the formation during drilling the hole 33 the string is supported by slips 28 on a spider 27 below the rotary table 24 during the addition of drill pipe sections, and these sections may be shorter than usual. The drill string contains a telescopic joint 31, and has additionally a centralizer 37 when the bit 36 is added. The joints in the drill string between the bits are locked with a thermoplastic material. The conductor may have a base 40 provided with guide lines 41, 42 and is connected to a running string 44 during installation. Drilling is carried out during a falling tide or during a period where the drop in tide is greater than any rise in tide.