Hi Thiha,

First of all, you have to satisfy whatever is required by the Govt Regulations in the area that you are drilling.

Secondly, you have to meet the Company wide guidelines of ENI.
I don't know what they are, but would hazard a guess that they are based on either Oil and Gas UK abandonment guidelines (Well Decommissioning Guidelines Issue 6 of June 2018) or Norsok D-1010 rev 4 as noted by Peter.

In most cases, satisfying those two requirements will pretty much dictate where you need to have barriers to ensure zonal isolation and therefore where you HAVE to cut the casing (as opposed to NEED to cut - which may be different).

Your program should then be based on cutting the casing at a depth which is as shallow as possible while still enabling you to meet all the criteria.

There may be other factors which could also be taken into account, for example, if you need to recover the casing for use on another Well.

Lastly, how you complete the final section of P&A depends on whether it is Land, JU, Platform or Semi/Drillship.

This is what i would do. 

What the the government, licensing, regional rules regs?
What do they state?
What is best company policy standards, best practices, or lack of it?
What are best guides to follows
- UK Oil and gas abandonment guidelines.
- Norsok D-1010 rev 4.
You wont go far with these its all spelled out quite clear.

You then  have to go back several steps to review the DDR's and gather that 17 1/2" drilled section, the trip the casing running and the cementing. Where are the risks when you come to abandon this section. Where is the top of cement. How did the cement job go. etc etc. Then the well life cycle evidence that may have changed any well barrier integrity.  

For fixed rigs any annular pressure build up? Hook up a gauge on the outlet valve and verify? 

On a subsea well you don't know until you cut with a marine well in place and annular close etc. Cutting in a higher risk well can escalate risks.

Rule of thumb leave everything where it it.
Cut as shallow as you can and deep enough to set primary and secondary barrier cement plugs required.

Where on a surface well head cut we generally cut deep enough so that if first cut fails as it does on occasion, We have left enough room for that second attempt. 

Offshore if there are no marine activities. Filling the well with enough cement plugs putting a cap over it, offers more advantage and disadvantages in our view. We did a review and made a report on this. We identified 6 things to consider. Of which all generally pointed to leaving all in situ! 

Some areas do this all the time.

Other areas categorically for no real and evident reason inform you all has to be removed from the seabed. At far greater time, ecological, and environmental safety and risk was our conclusion. 

What else we can try and help/assist further. 



  

  Agreed with Dave, particularly with heavier more difficult to handle big strings or semi cemented and  cemented multiple strings.

  I have been on jobs that have surface gas leaks after deep surface casing abandonments and re-entry becomes that much more difficult or impossible.

Hi Dave,

I am totally with you on "don't cut the casing any deeper than we absolutely need to" because it will absolutely have cost impacts.

Appreciate your idea , response and sharing. 

Hi Thiha

I'd like to add an additional consideration into the discussion, one that I cannot claim to be my own idea, but one that I really liked when I heard about it.

There is an operator who has always been at the fore-front of DROPS (Dropped Objects Prevention).  More recently, they have been championing an approach called "Let's Lift Less". A fundamental aspect of their thinking is that you can't drop something that you don't lift!

I read that this thinking extended to avoiding any unnecessary lifts and went as fas as, "don't cut the casing any deeper than we absolutely need to", so that we don't have to handle any loads (lifts) that we don't have to.

Over the years, I have read people sniping away at companies that "put costs before safety", but this is a great example of a company that puts its money where its mouth is.

Well done to them.

Kind regards

Dave

Gents,

Thank you for your time to answer my question.

@Andy, I wonder how you come up with 245 m for intermediate casing cut. What are the considerations to come up with 245m?

@Snas, Do you consider the environmental plug as secondary barrier? The way I understood from your explanation, it can't be considered as secondary plug as it is not verified after setting the plug. But I want to be sure.

Hi, guys:
Normally on offshore, the surface casing cutting depth is 10ft below seabed.In China, CNOOC company policy required 4meters below sea bed to cut all the casing and pull out. regarding to the intermediat casing, no required. up to the company.

Naung, 

Sometimes this is specified by local governmental policy. 

If no clear cut policy, intermediate casing can be cut 200-300m below the surface casing cutting point. This is to enable you to set a cement plug across the cut point and a bridge plug above to isolate /secure the well. 

In other words, if surface casing cut out point is 45m, then intermediate cut off point could be around 245m. 

HI Shahkamal,

Thanks. We didn't find hydrocarbon hence we need to perform P&A.
I found my answer from your respond.

Best Regards,
Thiha 

Hi,

I think provided information is not sufficient to comprehend the situation. Is there sustained casing pressure issue in the well? Why do you need to cut the casing for P&A? Do you want to recover expensive casing or part of company policy?

PS. We usually dont do that unless there is SCP problem. In a normal onshore well, just cut the casing stubs (below wellhead) near the cellar, fill annulus with cement, weld steel plate at the top of stubs. Fill half cellar with cement.

BR
SK

Thank you.