Patent GB-1244273-A (GB)
Title: Improvements in or relating to underwater well maintenance
IPC: E21B33/035
Filed: 1969-04-29
Abstract: 1,244,273. Boring earth; wells; caissons. MOBIL OIL CORP. 29 April, 1969 [27 June, 1968], No. 21728/69. Headings E1F and E1H. [Also in Division F4] Wellheads 14 are each connected by a production conduit 56, 76 having a valve 154 to a manifold 78 in a central station 10, a bypass passage 124 having a valve 148 and storage means for a tool 126 being connected to each conduit so that when the valves in a conduit and its bypass passage are closed fluid may be supplied by a pipe 122 to drive a tool into a well. A number of stations 10 are each surrounded by a group of the wells. The wells which are finally completed with dual completion well heads 14 are drilled from a vessel 32 the drill string 30 being guided by conductor pipes 34 mounted on template rings 51 fixed to a marine bottom. Oil produced from the wells 14 is separated by gravity via separators 72 at the stations to remove free gas. The liquid separated passes through lines 18 to a manifold 16 on an underwater storage tank 17 and then through a line 27 and a line in conduit 26 to a floating station 20 where it is separated, the finally treated liquid being returned to the tank through lines in a conduit 26 and a pipe 22. The stations each comprise a template ring 51 mounting the conductor pipes and wellheads, and open bottomed shell 15 fixed to the ring by screws 43. The manifold 78 is within a heat exchanger 74, oil from the wells being discharged from the exchanger to the separators 72. A water well 52 (which may also be one of the wells on the template ring) supplies water through a pipe 88 to the top of the exchanger to act as a heating fluid, the waste water from the exchanger being discharged into the sea through outlet 90. The exchanger (which may be dispensed with) supplies heat to compensate for loss of oil temperature due to the pressure drop between the wells and the separators 72 to prevent hydrate and paraffin deposits. The oil leaves the separators through outlets 98 and manifold 100 which is connected to the respective line 18 the pressure of oil preferably being sufficient to raise it to the station 20. Some of the oil separated in a separator 72 is led by a line 108 to a pump 112 by gas obtained from the oil produced and is pumped through a pipe 122 to drive a tool into a well. A two-way valve 110 permits a quantity of solvent from an open bottomed compartment 70 in the shell to precede the oil driving a paraffin cutting tool into a well, the tool permitting the solvent to pass the tool before a storm choke is reached. Gas from the separators 72 is disposed of through a line 130, a line 134 being supplied through valve 132 and leading to station 20 to be flared off if gas pressure is excessive. The gas may be led to the station 20 for combination with gas separated at the station and then flared or compressed for storing in tank 17 or another tank. The gas may be used for gas lift or for injection into a well which may be one of the wells in a template ring. Should the pressure in a well rise or fall excessively a valve 144 closes automatically. The operations may be controlled by an operator in the compartment 66 of the station 10, by remote control from the station 20 or by a programmed computer or by a combination of these controls.