Pipeline River Crossing 2

[bell99]

How is the required boring depth below river bottom determined for a petroleum pipeline?

 

[MiketheEngineer]

Probably the DNR - at least start there

 

[DLite30]

Depends on what kind of river you're talking about...if it's navigable, then the Army Corps of Engineers is the authority. T

Soil bores are taken to determine soil type/water and how deep you need to go inorder to get to a stable enough area in order control bouyant forces.

 

[rconner]

You have gotten some good responses. At some point, along with regulatory guidance and soil types etc. as they relate to pipeline stability and mechanical protection from detritus and anchors etc., a time history of the bottom profiles might also prove helpful for very long service lives (as I suspect some rivers and bottoms might well have a tendency to scour" maybe a little deeper than a meter or so bottom cover more quickly than the solid rock of the Grand Canyon has!)

 

[Duwe6]

And think HARD about sleeving your pipe. The mess in the Yellowstone River will end up costing 10's of $MM, for the want of a secondary containment sleeve.

 

[Adeelt]

Well i am facing a similar issue in a recent Project, Met a lot of HDD contractors recently. For directional drilling work to perform safely no one recommended a depth less than 8 meters below sea bed. They would perform their own Pull Force Calculation and Hole Stability Calculaiton.

Anyways i have to do a comparison between HDD and Pipeline subsea dredging (Excavation and Back Filling). The sea bed is shallow so client is asking for a comparison. Anyone having background knowledge?

 

[BigInch]

If you are talking about directional drilling, it is ususally determined by the geometery pipe bending radius, rather than scour depth, unless you have a very, very small pipeline diameter.

If you are talking about direct burial, or thrust bore, then you are usually thinking more about scour depth considerations, because the geometry of the pipe bending radius does not enter into the formula.

Aside from those considerations, soil type may enter into the decision. Looser soils with rocks should be avoided in most cases which, if rocks and boulders are prevalent, they should force you to choose a different depth.

Don't forget to evaluate the potential for erosion of the setup location and banks while you are at it.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[racookpe1978]

All of my piping work has been "out-in-the-air" plant and turbine installations, (never cross-country pipeline work) so please forgive the very real ignorance.

In a pipe going under a mud-deposited river regularly scouring even more tons of mud from the banks like the lower Mississippi or mid Missouri, where the river bed itself is "solid mud" and almost fluid, how do you get down under the dirt under the river bed? That's got be several hundred feet down in the lower Missip. Worse, the loops and meanders are eventually going to wash out the pipe embed's on both banks aren't they?

Will that problem be different for water (heavier than the river water) oil (lighter than river water) or natural gas (significantly lighter than river water) for the fluid carried? I can see a pipe being brought intact across ther iver and deposited into the bottom muck, but then it would appear you'd need to get the pipe into a "ditch" already dredged in the river bottom - then re-buried somehow.

 

[BigInch]

You have to first realize that loops and meanders are not a good place to run a pipeline. Look for a place where you can cross with a more perpendicular angleand where the banks are stable.

With a horizontal drilling installation, (a bit of a misnomer in relation to thrust boring), you are installing with a drilling rig that has been backed off from the riverbank for what could be several hundred meters or more, and the drilling angle is much more horizontal than vertical, 20 deg from the horizon or something. When you initially curve down to the center of the river, then start curving the drilling path back upward to the surface on the other side. You thread that hole with a pull line. Then you redrill the pilot hole to your pipe diameter as you pull your pipe through.

The distance back off the bank will usually depend on your target depth at the river centerline and the curvature you can safely get with your pipe diameter.

The Mississippi can reach depths of 180 feet, thus you might have to back off a mile to curve down under somethign like that, but there are probably better places to cross as well.

For such major crossings, you will want to take a pretty good number of test cores to short list crossing points from a number of potential crossing points, study the results and take more borings from those shortlisted, until you can finally decide on the final location. The river is probably navigable, so ask the COE for advice at an early stage. You'll need their permit to do it anyway.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[BigInch]

If its mud, sand, rocks, or whatever your design depth will be set to be "safely" below the maximum scour depth that the velocity of the river can reach, as calculated from its water volume, as calculated from the rainfall rate of your design storm frequency.

Need a pipeline engineer yet?

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[cvg]

trenching to install a pipeline in the Mississippi River would likely never a)be permitted or, b)be feasible. If the pipeline is to be installed at a shallow depth than you would need to hire somebody like myself to carry out the river analysis including hydrology, river hydraulics, sediment transport analysis and scour analysis to determine the recommended safe burial depth. That depth would have to be approved by the USACE. Then hire an environmental expert to help you get your 404 permit. Otherwise, drill baby, drill

 

[BigInch]

Oh I think it is possible to trench the Mississippi with a jet sled, then S-say pipe in it, but then why would you want to. But that would still depend on if you can get the S into it, which you might not be able to do at the banks. As of many years now the only way I know of that the Mississippi, the Atchafalaya, the Missouri and similar rivers being crossed is by Horizontal Drilling. No muss, no fuss.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[racookpe1978]

Need a pipeline engineer yet?

8<)

Nah. The power plant owners tend to get nervous when their steam, oil, and condensate flow distances get longer than 400 feet. Much less 400 yards. Or 400 meters. 400 cubits even.

 

[BigInch]

Oil burning tank mentalities.

The gas turbine operators don't mind having 1000 mile long natural gas lines though.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus