GB855219A - Submerged wells - Google Patents

Abstract

855,219. Boring sub-aqueous wells. ZAPATA OFF-SHORE CO. April 9, 1959 [Oct. 27, 1958], No. 11993/59. Class 85. Apparatus for drilling a submerged well comprises a freely floating vessel 10 supporting a derrick 15 on a platform 14 overhanging the side of the vessel, and a support structure 20 mounted on the water bottom over the site of the well. The support structure 20 comprises a tripod with one vertical leg 25 and two inclined legs 26, 27 and is fixed in position by a pile driven through each leg. The pile through the vertical leg forms the top-most section of the well-casing and projects above the surface of the water. The derrick supports an I-section beam 17 which forms a guide for a trolley 8 which is attached to a travelling block 18. Suspended from the block is an hydraulicallyoperated power swivel 19 which is also guided from the I-beam 17 by arms 57 and rollers 58. The drive shaft 62 of the swivel is screwed on to the drill string 63 which includes a sub. in operation the rolling motion of the vessel is accommodated by the movement permitted by the free fit of the rollers 54 and 58 in the beam and by the flexibility of the drill string. Fig. 7 shows a view of the conditions after an exaggerated amount of roll has occurred. Vertical movement of the vessel is taken up by the sub in the drill string which, since it is mounted a constant distance above the drill-bit ensures a constant cutting pressure.