APPARATUS FOR EXTRACTING PETROLEUM FROM BENEATH A BODY OF WATER

摘要

1507958 Wells &c. ENTREPRISE DE RECHERCHES ET D'ACTIVITES PETROLIERES 14 April 1976 [14 April 1975] 15274/76 Heading E1F A marine riser which extends between a releasable connector 14 on a base 4 on the sea bed 6 and a platform 2 on a tower 1 pivotably mounted on the base 4 by a universal joint 5 includes a riser pipe 7 which is formed in sections joined end to end and is free to slide axially in a hollow guide shaft 11 fixed to the tower 1, the upper end of the guide shaft 11 being closed by an annular plug. e.g. stuffing box 18, through which the pipe 7 passes in liquid tight manner, the lowest section 13 of the pips 7 being joined to the section next above by a connector 15 which is longitudinally slidable in the guide shaft 11. As described the connector 15 (Fig. 3) includes threads 35, 36 for connection to the sections of pipe 7 and includes PTFE rings 39 resting on flange 38 and held in place by ring 40 and nut 41. The rings 39 are a sliding fit in a sleeve 16 which is releasably secured to the lower end of guide shaft 11 by a spring collet (not shown). Grooves 45, 46 and holes 47 permit the passage of fluid past the connector 15. In use the connector 15 acts as a piston, this arrangement ensuring that the bending moments of the pipe are uniformly distributed throughout the lower section 13 of the pipe 7. The upper end 17 of the pipe is connected to a constant tension device 23 and centralizers 12 are mounted on the pipe 7 within the guide shaft 11. The arrangement includes a safety valve 8' in the base pipe 8 which is closed when the pressure in control pipe 26 drops, the pipe 26 including a rupturable section surrounding the lower section 13 of the pipe 7. The invention can be applied to a riser pipe 7 consisting of production tubing or to a large diameter riser pipe 33 of elastomenic material, e.g. for conducting gases to a burn - off flare.