THE BRITISH DRILLING RIG OCEAN ALLIANCE UNDERGOING SEA TRIALS, IN THE MORAY FIRTH IN AUGUST 1988.

Ocean Alliance was built in 1988, at Scott Lithgow’s of Greenock and was the last vessel to be built there before the closure of the yard.

The reason that the rig is down by the bow, is because this was a part of the stability trials she was undergoing at that time.
A rig of the same design, Ocean Ranger, had capsized in the Atlantic in 1982. Because of this, a considerable number of modifications were made to the design of Ocean Alliance. Nevertheless, in spite of these modifications, special attention was given to the stability of the Ocean Alliance on these sea trials.

During the speed trial in the Moray Firth, Ocean Alliance reached a speed of 12 knots. The speed achieved over the measured mile was 10.77 knots. During the manoeuvrability trials, the rig was able to swing round in 3 minutes, using her eight x 4,000hp thrusters.
In trials of her dynamic position capability, Ocean Alliance was able to be moored alongside in Invergordon, using just her thrusters.

She was a dynamically positioned, column stabilised semi-submersible mobile drilling vessel. Displacement was 29,904 tons at the transit draft of 29 ft.
Displacement at the drilling draft of 80ft was 46,113 tons. Variable deck load was 4500 tons. Length was 390ft, Breadth 231ft and Depth was 143ft.
Propulsion was provided by 8 x 4,000 hp Thrusters, giving a propulsion power of 32,000 hp. This gave the rig a self-propelled speed of 12 knots in calm water.
Total power output of the 6 Pielstick diesel generators was 39,400bhp or 52,836 kW.
Water Depth capability as built, was 1,500ft using anchors, 3,000ft using anchors and thruster assistance and 6,000ft using dynamic positioning.
Dynamic positioning was achieved using eight x 4,000 hp computer controlled thrusters to keep the rig on location, in deep water.
During adverse weather, the rig could continue drilling in 50ft waves.
Mooring was achieved using 8 anchor windlasses, using 5,500ft of 3 ¾" anchor chain and eight 45,000 lb anchors, backed up by the propulsion system.
The drilling Depth, as built, was 25,000ft. The derrick height as built was 160ft and was rated at 700 tons static load.
Drilling Equipment consisted of the following, National 1625 DE Drawworks, National 750 ton blocks, with a Shaffer 600K block mounted motion compensator. A Maritime Hydraulics 3 arm pipe handling system, was used to handle all tubulars racked in the derrick.
A National 49.5" Rotary Table and two National 12/P/160T Mud Pumps, were also fitted.
Subsea equipment consisted of a Shaffer 15k 18 ¾" BOP, 21 ¼" Hughes Riser and a 55 foot Slip Joint with a 45 foot stroke.
Riser tensioning was provided by eight Shaffer, high pressure air/oil pistons tensioning riser via chains.
Cranes consisted of the following. A bridge crane, rated at 250 tons, for handling the BOP. Three National pedestal cranes rated at 59 tons, at a 30ft radius.
A 30 ton capacity bridge crane was positioned aft, for handling large diameter tubulars.
Accommodation was provided for 110 men.
The rig was scrapped in 2017. I think the photograph was taken by one of the crane operators, although I can't remember his name.