Well Integrity Technical Section

Hello everyone,

When radioactive source LIH, there are certain mitigations that shall be done, one of them is placing coloured cement in the wellbore. Question: Any reference or research study that cement will eliminate (or minimize) radioactivity level in oil and gas application (i.e slurry recipe, height, etc)

Thank you all, have a nice day

Hi there,

Shefiled University research project  was published in 2019, please see below:

https://doi.org/10.3390/en12122393

I hope this helps.

Farid,

Not exactly answering the question you asked, but many years ago when I was the Drilling Manager for a MOC in the GOM, we had accumulated a large quantity of NORM (naturally occurring radioactive material) from production flow lines and process equipment.  As was the practice of the day, we stored this material in 55 gallon drums in a remote part of our shore base.  

We had a number of old production wells to PxA offshore (on the shelf and platforms that would be removed eventually) and we paid crews to load the materials in 5.5 and 7 in casing with caps on each end and a simple hook that would let us lower these in to wells (several thousand feet deep) and then cap the lot with a bunch of cement.  We then cut off the well at the mud line and removed the platform.

Got our NORM removed (at the time, the only place to dispose was a location in Texas with a high cost of transport and disposal.  This was a cheap and safe solution.  

Doug White

Sugar Land

Farid,

Since your question is about risk assessment you may find this publication useful: Risk Assessment of Abandoned Radioactive Logging Sources in Oil Wells in Nigeria.

Also note that you must also set a whipstock above the cement plug to prevent accidentally re-entering the abandoned section.

I hope this helps.

Regards.

a lot of good info already provided on materials, and you've already mentioned the (red) colored cement. most important factors are that (a) the source remains in place, and isolated, forever;  and (b) that it's not in a position to contaminate, for example, an aquifer, oil/gas reservoir, etc. if neither of those can be guaranteed then should be fished.

PS: I like the whipstock idea, could be combined with, or replaced by, something un-drillable (old RBP?) to ensure the section isn't re-entered accidentally. red dye can easily be missed if no one is watching the shakers.

Hello Farid,

There has been some good feeback by Scott & Luis... here is mine, focused on RA and sources (if it helps).
RA sources used in oil & gas well logging (generally, sealed sources containing radioactive materials that emit gamma radiation) can create 2 issues: direct radiation (exposure, for humans) and contamination (for humans or the environment)... in the case you describe with a source LIH, unless this would happen really (extremely) shallow there should be no issue with exposure... radiations will be blocked by formations above (as I said, unless the source was LIH really close to surface... like a few meters). Contamination is a lot more tricky as this could potentially then spread to large areas... but for this to happen you'd have to 1- destroy the encapsulation and 2- bring the source material back to surface - which could typically happen if you redrilled or milled on top of your fish. This is why the cement can be made a warning sign through the use of dyes... or why ideas to place a good/solid barrier above to prevent accidental milling can also bring value.

Of course a solid register should be kept - with info made public / available to all.

Otherwise I'm fully in line with Scott that if the source, over time, could potentially degrade (through corrosion) and then release its material to a "valuable" ground aquifer with the potential for its contamination (as the paper mentions, sources could be Americium 241 and Cesium 137) then the source really should either be further protected such that this doesn't happen - or fished/retrieved (which might be easier said than done).

Rgds.

Hello Farid,

Good documents shared, thanks for your question and to contributors.

One point may be added, though obvious: risk-assess the need to RIH such source versus the LIH risk. Geosciences will understand if drillers present to them a fair risk-analysis concluding not to do so.

Not all such sources can be fished unfortunately (i.e; LWD with bolted/anchored sensors barrels into its drill collar). Although the source is encapsulated, fitted withing an instrumented barrel and protected by the surrounding DC wall thickness, in the long term, in a corrosive HC reservoir environment, leaks could occur, therefore no one would take the risk of compromising the whole field production. If LIH across an aquifer, even deep, but onshore, say in Europe with dense population and large regional aquifers, no one would take the LIH risk, the situation being different offshore far away from shore. Even a retrievable LWD RA source could be challenging to fish, i.e. in a horizontal drain, special tools and competent people are required, but you will hardly find LWD engineers with RA source fishing experience (RA source LIH is rare fortunately). Though Risk Assessment case by case is of essence.

With regards to NORMS, it is an extremely expensive business to deal with and no way around regulation (derogation) in some EU countries. It can be a nightmare when P&A if budget isn't provisioned for it. Some EU country regulation would require treating every tubular joints in special solutions in dedicated premises, and conditioning the RA waste solution in drums and storing in dedicated locations for long term, as well as for treated tubular. It seems to me a significantly increased risk of exposure during the treatment process and in the long term. Coil Tubing wash & squeeze, if workable (case by case), flushing the NORMS back into the reservoir where it comes from may be much cheaper but not always a regulatory option (neither a technical option in some case and if the P&A operation may be put a stake by doing so).

Regards

Régis