Sub-Sea Drilling Cassion

I asked and was informed that there is anywhere from 50 to 100 feet of soft mud in the area of the gulf well. I am not sure how you intend to anchor this caisson to the sea bed. It will sink in the mud (loon shit in Canada) and disappear in very quick fashion. The sea floor is not your typical beach. Unless you work on that problem I don' think the caisson is a valid solution. Keep trying.

Good point, but just like the massive Offshore platforms that sit on the continental shelf, sub sea piles are driven into the silt to bedrock. They are driven on a slight angle perpendicular to each other with the base being outward These huge platforms are designed to sit onto these piles. After the platform is set onto these piles anchoring piles are driven through portals prefabbed and located at it's base. Each platform as I remember has a triangular plate welded across each corner. These offshore platforms are all over the Gulf and the work is done underwater. It is this anchoring process that keeps these platforms upright and intact during violent hurricanes that produce seas as high as 70 to 80 feet high. This type of base support and anchoring has been around for close to 40 years. The same process could be adapted for deep water applications. I should have detailed that process. Also, when casing is put in over the production tubing it is also in most instances driven into the mud/silt to bedrock prior to cementing. The caisson say 45 feet in diameter with a 15 foot diameter hole for drilling would have an outside horizontal rim,( a skirt) on the Bottom surrounding it's whole circumference for anchoring purposes. The caisson would have a solid steel bottom with the 15 foot center donut hole being open. The mud and silt can be washed out with high pressure jets after the caisson is filled with concrete. It is hard to explain all of the details with out the drawing. I worked offshore for many years, When I first started, I worked during summer break from college, on large offshore Tugboats. We hauled out offshore platforms on barges and stood by while they were offloaded and sunk into position on top of piles and then anchored. I watched the process many times. It can be done. Using this caisson application would be expensive but it would provide an underwater secure weighted platform for a host of options. Not only will it be a base for the drilling operation, and containment option if necessary but also a platform for the production process for anchoring underwater deep sea trees. Tree is the terminology used to describe the delivery devices. A tree contains shut off valves multiple choke devices for controlling production. The caisson can also be designed with a yoke so the pipeline that attaches to the manifold off of the tree can be secured. The pipeline is what takes the oil to shore and then to the refineries. This caisson can be designed in a concentrated limited fashion theoretically just like the production deck of an elevated offshore platform. Again very expensive...BUT..very safe with numerous application possibilities. Thank you so much for pointing out the discrepancies. I would appreciate if you and others would add more comments to help improve the concept. If there was a way we could put up a drawing and modify it as we could all participate in virtually designing this structure by consensus. I wonder if there is a format to submit a drawing online and then edit it..well there should be. We do not need permission by the Oil companies to think out loud and find solutions that corporate fiscal constraints prohibit. I believe that is a major problem today, people are not allowed to think out loud with out their thoughts being sanctioned or politically approved. That is stifling to innovation. Thinking outside the proverbial box is what advances technology and civilization. It is obvious that the current rule of thumb of corporate restraint and political scrutiny is dominant in the problem solving process. Using the example of BP's approach and failed attempts to solving this unfolding catastrophe is evidence enough.

Thank you again for your response..and help me with this. I think it could be a vital contribution to maintaining the integrity of deep sea drilling since alternative energy,(because of corporate political influence), seems to be many decades away..even after the advent of this catastrophe. Realistically..Big Oil will be around for many more years.

jovian

Hello Jovian

I usually don't look at my computer on weekends so always a delay in placing a post at that time. My background is in water wells not oil wells.

I have thought of your plan and cannot think of a good way to drive a caisson that would sit on solid formation. This action may prove more problematic that you think. you must bear in mind that the well head is 5000 feet under the sea.

Your idea may have merit as a means of supporting a backup plug for oil wells. I am not sure if we could use the grouted annular space and the casing as a basis for building a much smaller caisson that could accommodate the drill casing, BOPs, and any other monitoring required. It would have to be secured solidly to the annular space and extend far enough above it. The idea here is to create a vessel with the well in the middle. If the well has a problem, then the vessel could be filled with a plugging material capable of withstanding the pressures and would not be thrown out of the vessel by the upward pressure from the gas and well. This operation is likely to prove very difficult to implement. So we still need some method of shutting down or directing the flow of oil and gas in a controlled manner, like a pipe in the plugging material perhaps equipped with a working BOP.

The caveats here are the securing of the caisson to the well construction, and if the well needed to be entered or casing worked on it may cause future headaches. I think the mess in the Gulf will prove profound enough, that ideas will be explored to stop another well from getting out of control. We may require the oil well construction to incorporate backup plans like relief wells already drilled and perhaps a caisson. I think the rules will change once the dust settles with the Horizon well. This is a good thing as the Arctic ocean is about to open to oil exploration. Keep thinking outside the box

Thanks again for your response.

When wells are drilled in shallow water the first exploratory well is usually drilled from a Jack up Rig. Once a promising location, (oil pool/oil formation) is established the well is capped. After this process takes place..a very large, very expensive drilling platform is placed over this well. The platform consist of 2 components,(sometimes 3 in depth over 300 feet but less than 600 feet. The bottom section is called the jacket. These structures are as big as a football stadium 350 high feet by 200 feet in width. They are prefabbed onshore and floated out on Gigantic specially built barges. Once on location one end of the barge is partially sunk via ballast control. The jackets are slid off the barges, they float. Ped cocks are opened on the tapered end ,(the upper section), and over a period of time they are sunk into place with the aid of huge derrick barges that are attached to the to the top of the jacket via huge slings. The jacket is then placed over a set of piles that are pre driven around the original well the outer edges of the jacket's corners. Again at each corner is a triangular steel reinforced plate. These jackets have numerous drill ports located in it's center usually encompassing 2/3's of the center. In other words they have predetermined brackets that are fabricated to accept multiple casing and well piping. Of course the Blow out preventers are above water and usually under the rig on the production deck of the top structure called the Platform. After the jacket is in place, piles are driven at the corners though prefabbed circular steel brackets that are welded to the jackets steel piping at the corners. All of these piles are driven by a huge steam hammer/hammers located and suspended from the derrick barge/barges, ( multiple barges are sometimes used). Also, when needed, an extended heavy steel capped extension pipe is used to drive the piles in deeper water since the hammer on the driver is not submerged. It must be noted that shallow water offshore sea bottoms have a thicker layer of silt sand and mud than outer continental shelf depths..so piles are driven deeper to bedrock. Now , after the jacket is placed, it usually sits about 10 to 15 feet above sea level, the platform is bought out and placed on top of the jacket. This structure is a pure vertical structure. In other words the corner legs are not slanted outward like it's base structure.. the Jacket The platform form is designed with 3 decks, from bottom up at 50 feet up is the sub deck, at 65 feet up is the production deck, at 90 feet up is the drill deck or the top deck. The sub deck and the production deck has the same openings as the seafloor openings on the jacket perfectly aligned to accept casing for additional drilling. The drilling rig is now brought out and assembled in modular units to continue drilling other wells. The original well is re opened and put into production once the upper tubing, inside casing, and outside casing, extensions are attached and the production tree and manifold equipment is attached. The manifold rack, test separators, and piping all have been prefabbed and are part of the upper structure before it is brought offshore. Everything is pre tubed. After the original well is ready to flow the pipeline riser is brought up from the sea floor and attached to the discharge delivery piping from the production manifold. The well is brought on line and production begins. While all of this is going on The Rig has already begun to directional drill perhaps as many as 15 to 20 additional wells all connected after completion is the same manner. as I previously mentioned, I have seen this process take place quite a few times from the deck of a large towing vessel while on standby with the Derrick Barges during summers of my college years. It is a common practice in the shallow offshore Leases or drilling blocks. When I became a high pressure gas consultant later I also witness many drilling operations from these sea bottom attached platforms. I lived on and worked on a production drilling platform for 3 years, (7 days on, 7 days off), while wells were drilled one after the other. It was my job to bring on line new wells test them periodically and establish optimum flow rates that were safe and insured long term production rates.

The caisson I am talking about takes the same process and puts the platform on the sea floor. There may have to be a larger annular to accommodate multiple casings or a series of cassions placed in a cluster. These cassion underwater platforms certainly can be designed to not exceed the extreme weight of their shallow water counter parts the Offshore steel Jacket/Platform system. They both sit on silt and sand and pre placed piles and both are pile anchored. As I said previously having a stable platform with substantial weight and pre placed attachments for a variety of applications allows for quick response to predetermined situations. If you look at my first post you will see that the large dome with the gate check valve could be attached to pre placed attachment devices. Say 2 to 3 domes could be prefab and placed along the Gulf coast at ports for quick access and delivery in the event of another drilling catastrophe. We should be finding a reason to design a deep water platform of this type rather than finding a reason not to. Never the less it is sound logic and something of this nature is necessary. Again it is not Rocket Science. The platform placement technology for shallow water already exist and has been used thousands of times supporting huge amounts of weight on top of hundreds of feet of soft silty sandy sea bottoms in the shallow production coastlines of the Gulf of Mexico. The weight is tremendous picture a jacket the size of a football stadium with a Platform on top with heavy production equipment, with a drilling rig on top and a living quarters also on the top deck..thousands of tons of weight..It can be done. Again a drawing would be the appropriate way to address and modify the Idea into a confirmed application. Right now it is certainly plausible..pending details and engineering standards.