Oil & Water

Got this email from a cousin. My reply follows:

-sundar.

It has been decades since you were on an oil rig. But what kind of safety organization do they use in the rigs? Is there anyone on the risk management/evaluati on side of the ops who could veto decisions of other departments? Order a well to stop pumping or take steps to ensure safety even when it results in huge losses due to lost/curtailed production?

The one where I worked for two years (1987-89) is an Offshore Oil Platform named SHP (see picture). Rigs used to move in, drill the well and move out. But platforms used to be installed as permanent structure after the rig moves out to collect the oil, water & gas mixture that comes out, separate water and pour it back into the sea after cleanup, separate oil and gas and pipe it to the shore using submarine pipes or tankers for production of various fuels and petrochemical products.

In my days there used to be one big platform roughly for each 100 square mile area where deposits are found. It used to have about 100 people working (half contractors doing cooking, cleaning and half ONGC engineers) in shifts throughout the day. This one manned platform will receive oil/gas/water mixture from about dozen unmanned platforms located radially all around at a distance of 5 to 10 miles. Each one of the smaller unmanned platforms in turn used to have about 10 oil wells each. Each well will be tapping oil at an angle forming sort of spokes emanating from the platform that covers a circle of say 2 or 3 miles. Thus, each manned platform will be processing fluids flowing in from more than 100 wells.

Depth of water in the Arabian sea off the Bombay coast used to be about 230'. Depths of oil wells used to be about 2 km beneath the seabed. You can think of the jack-up rigs used there as a triangle plane with three legs on the three corners that can slide up or down. Legs used to be about 300' tall. So, the floating rig with its 3 legs sticking up 300' above water surface will be brought into place where a new well need to be drilled. Then the rig engineers will lower the legs in hit the seabed. As they continue to 'lower' the legs even after they hit the seabed, the triangular rig plane will raise above the water surface another 50' or so. After making sure the legs are anchored properly, the rig will drill wells going down 2000 meters or so to tap the high pressure fluid there.

Once tapped the fluid mix will come up at around 2000psi pressure there. So, every well used to have a safety valve called SSSV (Sub-Surface Safety Valve) that will be at least couple of hundred feet beneath the seabed. Since it is a safety valve, by default it will remain closed. From the platform above, there will be a hydraulic oil line that will run down to this valve. We need to use a small pump (size wise similar to the pumps we can buy in Walmart for $20 to pump air into the car) using which we will pump in oil and build the pressure up to about 2200 psi to force this valve open. When the fluid reaches the surface there will another safety value called SSV (Surface Safety Valve) that is kept open pneumatically. If either one of the two pressures go down, the well will close automatically.

Blowout Preventers used during the initial drilling process is functionally very similar. They also have additional sensors to sense the amount of pressure being exerted by the fluid flowing in from below as well as the amount of flow. If those values exceed set limits, it can trigger well closure automatically. Once the drilling operation is complete, each well opening used to have a final opening of just half an inch or 3/4th inch diameter..! In Bombay High Offshore fields, about 1000 barrels of oil used to flow per day through that little hole. This is considered low compared to US and gulf wells that yield more than 5000 barrels a day. If the opening is made bigger (say 2 inch dia), more oil may flow out. But it will also bring out more natural gas which is needed to get the oil out. So, making the hole bigger will yield higher production initially but the well will stop the yield prematurely with lot more oil left below with no gas pressure available to push it up. So, the opening diameter is computed to get as much oil out quickly while also ensuring all the oil that can be retrieved is brought out. If the gas pressure has gone down considerably to get the oil out, there was also the practice of injecting water into the oil basin to raise the pressure again to get the oil out.

On the platform safety is a big thing and everyone used to be worried since we all knew we were living inside a bomb..! There will be a safety officer who has to certify things are in good shape everyday. Field Production Supdt. (FPS) is the boss for the whole platform and is similar to a captain in ship and so is responsible for overall safety of the platform and crew. For a public sector company, I found the morale, cohesiveness of the crew, how well people treated safety issues, etc. to be quite commendable. The underlying realization that "if it blows up we will all be dead" kept everyone on their toes. For example, while we are allowed to wear non-cotton clothes inside the living quarters that were positively pressurized, we were required to always wear bright orange colored cotton boiler suits outside the living quarters since it will not burn that easily and it will be easy to spot anyone accidentally falling off of the platform into the sea. If newbies step out of the living quarters area even for a minute in clothes not up to code, anyone/everyone will jump on them and pull them up by their ears.

There used to be ESD (Emergency Shut Down) and FSD (Fire Shut Down) valves allover the platform once every few feet. So, anyone can potentially trigger a platform shutdown in a second. Of course proper shutdown may take couple of hours to complete from the instant it is triggered to burn up all the gas using proper vents, shutdown equipment, etc. As this will result in major production loss, it is not easily activated. Still every Sunday we used to have practice sessions on how to abandon the platform, board the fiberglass life boats and leave the platform, etc. I have gotten on those boats, with other crew members, lowered it to the sea, started the engine by hand as well as hydraulic means, disconnected the steel ropes and drove the boat around to make sure everything works and we know how to operate it.

At every level of hierarchy there were powers given to people to stop production if safety is an issue. When I was there a rig in the North sea of England went up in flames. It was used as a 'teachable moment' to make people understand what went wrong in that case and to have a safety review. Once when I flew to an unmanned platform for some routine maintenance and returned to the platform, I got off of the helicopter and by mistake got down from the helipad to the platform surface using a wrong set of stairs on the side of the helipad instead of the helipad stairs located in front of the pilot so that he can see us getting down and take off. The radio officer inside the platform watching the helideck to manage air traffic, promptly reported me to the FPS. As a mild punishment I was asked to deliver the safety lecture that Sunday discussing helicopter safety with the platform crew. They didn't know I was working for HAL's Helicopter Design Bureau in my previous life. So, I just blew their socks off with my presentation on helicopters, various forces in play (thrust, drag, lift, gravity), how the main rotor and the tail rotors work in sync to keep the aircraft straight, using collective and cyclic pitch to fly the craft, how dangerous it is to get near the blades, etc. Ravi would have been proud of me. :-)

To keep things in balance, we were given bonuses when intended production quotas were met. So, people had interest in getting the production going. Since production from each well is quite important, if a well shuts down any time of the day, we (maintenance engineers) will be pulled up to go fix the issue asap. In my personal experience, I have been pulled up from my bed in the middle of the night to gather tools and head out with a small crew to go open wells several times. Using the platform crane we will be lowered into a small ship waiting next to the platform in a basket. Once we are on the ship/boat, it will take us to the unmanned platform some 10 miles away that has stopped sending oil. By the time we reach the destination it may be say 1am. Since it is unmanned, there will be no light. Since wells are shut down, it used to be eerily quiet. We used to do a Tarzan swing using the ropes hanging from the platform to get on its lower level (quite safe since we used to wear safety jacket and the boats used to get quite close to the platform if the sea is not rough) and head up to figure out what went wrong. Emergency generators may not work and so we will be dependent upon flash lights. The pneumatic control panels that control the wells SSSV and SSV all are operated using the natural gas flowing from the well itself. Some amount of the gas is separated and saved into a small tank that functions like a battery. We have found broken pumps or leaky pipes that blew the pressure shutting down the wells. Use to mend them with the tools & spares we have carried and reopen the wells. Hearing the loud & healthy hissing noise with which the oil & gas mixture starts to flow will be music to our ears and an indication of mission accomplished. :-) By the time we call the boat to take us back and return to the platform it will be 4am. Great experience.. !

The Louisiana Deepwater Horizon rig was operating in the ocean that is 5000 feet deep that could complicate a lot of things. It is private sector operation with several levels of subcontracting that may lower safety limits. Still I thought compared to my experience that is more than 2 decades old, technology would have grown by leaps and bounds by now, rigs and platforms will be extremely safe, etc. Goes to show how naive I am.

-sundar.