Tag Archives: seismic

Seismic survey in the North Sea, 1989

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Starting work at midnight, everyone piles into the instrument room at the absolute last possible minute. I’ve been on crews where you start work at 11.35 and your oppo leaves exactly at midday or midnight. On this crew, it was the other way round – you start work exactly at just before 12, and your oppos leave about 12.25 or so, earlier if possible. It doesn’t matter which you do – so long as everyone does the same thing.

We’re in a long line change. The first thing we learn is that all the starboard guns are on deck for repairs and the gun mechanics need a hand. Us two assistant observers head for the gun deck on the instant, followed later by the Observer, once the handover is complete. There are several problems. A supporting U bolt needs replacing and welding into place. One gun has a water leak in the umbilical line. Another gun needs it’s actuator replacing. This last we can do; it’s just heavy work with spanners. All three observers and all three gun mechanics work hard for a while, and eventually all the tasks are completed. The guns are launched at the last minute – only just in time as the survey line starts.

We shoot the survey line; it is mostly uneventful. An observer watches the tell-tales on various computers, of the seismic cable and the guns, and the navigator (or surveyor) steers the ship. It is 3a.m and blowing Force 5-6. There is some swell noise on our seismic recordings – that is, the sea is rough enough to start distorting the reflected noise from the guns when it appears on the seismic streamer, which is towed around 8m under the sea surface.

After the end of line, I perform a set of daily diagnostic tests on the recording instruments. This is a contractural requirement. It’s routine work but we do it for a reason, to spot problems as they crop up. After the test, it is 7.50a.m. My colleague replaces me watching the streamer, and I go for breakfast: sausages, bacon, tomatoes, chips, toast and marmalade, and tea.

We come round onto the next line, and prepare to start shooting, but the wind has risen to Force 7-8, and the swell noise in the direction of the line is unacceptable to us or the client’s representative. We have some options on this prospect – we can swing round to try a line in a different direction. The new information is programmed into the navigation computer by the trainee navigator, his boss keeping a watchful eye. Time passes: the swell noise is no better.

Then there’s a call on the intercom from the bridge, about the rising wind and worsening sea conditions. We agree; it is too rough to continue shooting. I’m despatched to the mess to tell the gun mechanics to stand by to recover all the guns. By now it is Force 8 outside and Seismariner is starting to move. The guns are recovered in stormy weather. Driving rain is hammering down, hissing on the surface of the sea. Because of the weather it takes a while, about an hour, to get all the guns aboard safely. Next, I accompany the chief mechanic and a gun mechanic up onto the quarter deck to help bring in the booms. These extend 21m either side of the vessel and are controlled hydraulically. It is pouring with rain and a sharp gale is ripping at our clothes. We’re all glad to get back inside afterwards and clean up.

I sit down shortly afterwards in the instrument room with a cup of tea. Everyone is sat around, talking. The wind is still Force 8. It’s not a BAD storm, but storm warnings are being broadcast on the teleprinter. The words “cyclonic depression” are seen. It is 10.30a.m. Suddenly, Phil, the deputy party chief, makes his decision – “get the cable in!” We stare: it’s a three-hour job in the wet and cold, and hard work. We finish work at noon…

But Phil has a hunch about the weather; that’s what they pay him for and he is right. There’s a delay about then as a trawler crosses our stern about a mile back – on top of the cable. Crash dive the cable. Fire flares into the rain and wind. By the time we start recovering the cable, it is 11.15a.m. One or two out of every five waves or so is slopping into the back deck and getting us wet; it is quite rough. Progress is slow, pushing and shoving with no hydraulic support. It seems to be getting calmer outside. It IS getting calmer; the sun appears. We wonder at our bosses decision. He appears on the back deck, telling us that Seismariner is in the eye of the storm – the “cyclonic depression” he saw on the teleprinter earlier. The sea goes down to barely 8 or 9 foot waves.

All of a sudden though, just about noon, the wind comes up again, from a different direction. Foam and spray are everywhere all of a sudden; the sea is white. Phil’s boss, the Party Chief, makes a rare visit to the back deck and endorses Phil’s decision: “Get it in QUICK” he says. The wind is now Force 10 and gusting to Force 11.

A toolbox talk

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As part of my last job I was a coxswain of small boats. Not an instinctive driver of such boats, nor even a particularly brilliant one, but nevertheless a perfectly competent one. Small boat driving was the one area of my job that has given me the most satisfaction, though it wear me out from a purely physical viewpoint. This story is not really about driving small boats as such, but is the tale of an incident in a small boat that involved me. It has stuck in my mind for a number of reasons, not the least the gorgeous weather at the time.

On a time four of us were out in our Norpower 25’, a sturdy dory or work boat with a big diesel engine and huge propeller; it was a calm and sunny day in Tropical waters, in late afternoon. Our task was nearly done – I shall not attempt to describe that task in detail, save to say it involved the boat being physically attached front and back to a long cable towed through the sea. Our task was to replace a section of that cable, a piece some 100m long. We brought with us a new section, wound on a reel, and we would take home the damaged one we would be removing.

The time came to free ourselves from the cable, which being many kilometres long and towed from a large ship – our primary work place and home away from home – was under perhaps a ton of tension. Hydraulic pumps and winches were to be used for this task. We went to do this task, and nothing happened when we moved the control levers. This was a worrying moment, but we gathered our wits about us, as we had been trained to do, and soon enough after a brief search, we found a leak in the hydraulic control equipment. This meant that it was no longer possible to free ourselves from the long cable using machinery. The time was around 4.45p.m, and we found ourselves in a potentially quite hazardous situation. We were in a small boat on the open sea, attached to a cable without the obvious means to free ourselves, unable to navigate or control our boat, and to make matters worse, about an hour’s journey from the mother vessel, with perhaps ninety minutes of daylight remaining.

It so happened that on that occasion I was a workman – I was not the Coxswain. It also happened that I was far and away the most experienced and senior person in the boat. What did we do? It is instructive. We paused to discuss the problem. This is a technique we use regularly in our industry, a technique proven to reduce accidents and injuries in the work place – the concept of the “toolbox meeting”. Then, the coxswain, a young woman, call her K, yielded the helm to me as the more experienced person. We had to get the cable free of the back of the boat. Since we were towed from a rope attached much further forwards, we contrived to let out that rope manually, by letting the brake on the winch slip. This enabled us to free ourselves from the cable at the back of the boat, though not without some difficulty, and the task took fifteen minutes. As the sun sank to the horizon we were conscious of impending darkness, ever aware that the run back to our mother ship, would take most of an hour.

Nextly, as Coxswain I caused the boat to move forward, such that the rope on which we were towing became slack, and the boat was under way independently. This was a delicate task involving some concentration. Slowly then I ran the boat forwards up this winch rope, and my colleagues looped the slack into the bows of the work boat, since the winch, being hydraulic, would not work. It was a 200m long rope and by the time the task was done, there was a blazing sunset, a picture of glory, the sky painted red and gold and pink and orange. The final task was to remove the clamp that held the rope to the cable. This, though a delicate manouvre, is one we were all well familiar with, and in moments we were free of the cable and clear to go home. A potentially disastrous situation had been averted, through teamwork, clear communications, strong leadership, and familiarity with emergency procedures.

It remained only for us to motor the 4 miles back to our home away from home, this task taking getting on for a full hour since the ship herself was making 4 knots away from us, and the work boat could only make 10 knots. It was nearly dark when we arrived back, and we were well ready for our dinner after such an exciting adventure and – truth be known – such a narrow escape.