Soil improvement for Dredging and Oil platform structures

[Ariel26th]

Hi Everyone….

I’m sorry if I post to the wrong forum, (please refer me to right one)

My company currently still in the Conceptual Offshore Oil and Gas Development in Asia, The reservoir that we have lies below mud flats and Peninsula that I should say very Challenging in term of Execution to build Structure/Platform on the land since there are no access to the area from the land (Mangrove area), if we would have to do it from offshore it cannot be far from the reservoir target (Drill Cost!) so we have to build them around the area near the target or I should say mud flats ranging from 2 to 4 meter water depth. The soil issues are:

1.Soil analysis indicates that dredging will be ineffective due to the lack of cohesiveness of the soil.
a.Extremely Soft soil until 100’ of soil depth(Soft Clay > 80% water) based on soil survey
b.Stiff Clay only exist beyond 100’ (Stiff Clay < 50% water)
2.Dredging would be required for installation Vessel access of the structures and Drilling Rig access (Swamp Drill Barge operates minimum 5 meters)
a.I guess based on soil survey above dredging nearly impossible
b.Possibility of using sheet pile around to coffer dam the area and use Suction dredging
3.Soil improvement to support the drill rig position when it grounded down
a.We try to use pile and compacted soils and sand bags

Have any of you had similar experience that you can share…

Are there any specific Expert Soil Consultant that we can use in this kind of shallow water to investigate the possibility and method for dredging the area, and an experience Dredging Contractor that we can seek for advice?

Sorry for the long intro and thanks for your insight….

 

[BigInch]

Dredging doesn't sound impossible, but I'm not looking at the soil report.
Get the barge in there. Convert to, or replace with a production barge.

Production barges are available.

http://www.onepetro.org/mslib/servlet/onepetropreview?id=00017669

Independent events are seldomly independent.

 

[Ariel26th]

Thanks BigInch...

yes i have heard about the Converted Production Barge in lieu of Fixed or FPSO type facility, the reason why it can not be floating type on my case, since it has to have fixed position for drilling and pipelines to the other facilities, the floating type is used in conjunction with the sub sea well tie in, and on my case as well i can not use sub sea due to the Water depth Less than 4 meters and the mud is more than 10 meters deep. The challenge is the drilling cost would increase significantly if i offset to a deeper depth if i want to use sub sea or any conventional type.

 

[BigInch]

Your argumenst for the need to have a fixed structure for drilling are weak and not convincing. You will need to set the wellhead assembly at barge deck elevation, really just a few meters higher than the mudline. You will have to solve bringing up the well to that elevation with a strong casing through the weak soils, which you will have to do in any scenario.

The pipelines may actually present a more difficult problem in the weak soils, since if too negatively buoyant, they will sink down too far into the mud, yet if neutrally, or too, buoyant you may not have enough stability during storm, current and tide conditions to keep them from floating away. Apparently you cannot atttempt to let these sit on the soft mudline. Also apparent is that you cannot fix a pipeline end manifold (PLEM) to anchor the pipelines with the PLEM structure on the all too soft mud near the wells to run flexible lines from the PLEM connecting to the well heads, as is the common solution for offshore buoy un/loading terminals and the like.

I believe that you can drill from a barge, even though it is not a permanently fixed structure, and I would attempt to solve that little pipeline problem by eliminating pipelines entirely, in favor of a shuttle barge. More expensive than pipelines, but a viable method of transferring the oil ashore, if it is impossible, too expensive, or too unreliable to attempt to construct pipeline(s).

If I were you I'd start concentrating on ways to solve your problem, instead of inventing justifications for why nothing will work. I don't believe you want to do that job, so why not just give it to someone who does.

Independent events are seldomly independent.