Scraper run before running liners
23 August 2019
At a recent DWOP, we noticed that the team are planning to run dedicated scraper runs before running liners. This is due to "problems" in the past with liner hangers/packers.
We have not come across this practice before and would like to hear your thoughts (and, in particular, experience
- Who (out there) is making dedicated scraper runs? (and WHY)
- Who is not and what problems have you ever had?
- What other options are there (such as RFID-activated or ball/pressure activated scrapers) run with the drilling BHA? And what experience/best practice/ lessons from them?
As I understand the query, the team wants to do a dedicated scraper run prior to running a liner due to problems experienced in the past.
The question I would have is, does the team fully understand the problems experienced in the past associated with running of liners? What is their failure rate?
Would it not be useful to investigate the root causes of the failures as opposed to relying on some anecdotal evidence?
The other important issue to consider is the type of liner hanger used or considered for future wells. Different suppliers have different systems and therefor different requirements. Nevertheless one should always challenge the recommendations taking into consideration the actual wellbore conditions.
The question is not just related to running of liners, but could be transposed to running of cement retainers and casing packers as well. Indeed, ideally, as per the recommendation of the service company, who are typically risk adverse, one would want to run a scraper. However, cement retainers and casing packers (think TAM) have been set successfully without a scraper run.
Perhaps not answering the question ... but hopefully provide some guidance to the team to challenge convention and base decision on facts rather than anecdotal evidence (which unfortunately our industry is saturated with).
On a new well, with new casing, I have not run a scraper first. And the jobs were successful.
However it depends upon circumstances. Old well? History of crud?
It is not a wrong decision to run a scraper if success is in doubt.
However I smell a confounding factor..........are you running a Liner Packer??
I adhere to the view the the Liner Packer should be run separately after the cmnt job. This means a clean out run, a polish run to TOL and then a separate run to set the Liner. And always a good Liner cement job.
so.....if you want to save time and include the Liner and Packer together even if you have a separate scraper run you would still be ahead on timing but..............whenever you run the packer with the Liner Hanger there is always the temptation to go ahead and set it before the results of the cmnt job are known - after which it is convenient to ignore the requirements to obtain cement integrity around the Liner top. And becomes somebody else's problem.
During my tenure the sacrificial scrapers were the recommended.
In the '80's and early '90's, it was fairly common to do an old-fashioned casing scraper run prior to running a liner hanger system as integral liner top packers were just being introduced and when you ran a separate tie-back packer, before integral ones, nearly everyone ran a scraper with the liner top dress mills, so it was a carry over from that.
To be fair, pre-90's casing scraper designs were pretty in-effective anyway. As time went on into the '90's, the industry realised that it was possible to fore-go the scraper run before a liner hanger with integral packer most of the time, so long as the plugs had bumped and no drilling of cement took place at the new liner hanger depth.
Running scrapers and brush tools came back into play in the mid to late nineties, because more and more cement-less final string liners started being run and the packer integrity became more important. Some times you would run the scraper or brush directly above the cement-less liner hanger and brush and scrape then pick up and set the hanger/packer in that cleaned area then POOH.
In the '90's and early '00's , PS was the go-to company for these kinds of drill string deployed tools that had been designed to be more effective.
In the '00's, Caledus came on the scene and their Australian office helped to cause the introduction of Brush and Magnet tools to be run as an integral part of the liner string just below the liner hanger and packer, these were in-line on casing hulls or clamped on. These Disposable Brush/Magnet Tools were run quite a lot with screened liners.
Truth be told for the cemented liner hanger with integral packer a dedicated scraper run should not be necessary, however if a low risk method of doing it exists on the last drilling trip or with the liner itself it would assist.
There certainly have been liner hangers that slipped down and would not set and integral liner top packers that did not seem to seal, even though set. Good practice is not do set the liner hanger or integral packer in casing above the shoe track were drilling tools have been rotating whilst drilling out the shoe track, so the liner hanger and packer would be up inside the previous casing by at least the length of the drill out BHA.
We do scraper before setting tie-back packers at TOL, after scraper operations, circulating until the hole is clean.
We don't do scraper trips prior to running liner's and haven't had any issues with setting packer's due to that.
We've ran almost 100 + liners with the same strategy so far.
Without discussing the pros v' cons of running a scraper prior to the liner let me answer your final bullet point.
MI introduced the Switchback scraper (ball activated) around mid 00's - which could be run in the string, ball activated, but requires to be reamed to scrape (similar to an underreamer).
In 2015 when working at Odfjell I patented what would become the DrillRdillo - the main difference is the tool scrapes using reciprocation, which saves considerable time. I see they have been running this more frequently. The initial requirement was to scrape 9-5/8" lower completion packer depth after drilling to TD on a OHGP well where there were time related issues with the formation (short window to get screens in before formation causes deployment problems) eliminating the need for a dedicated cleanout run.
We obviously pitched this as a potential pre-cemented liner run solution and the discussion we had with operators were similar to the comments posted already, dont run it if you dont need it, which is fair. That said several operators do experience regular problems setting the liner, and the added assurance of having the tool made sense to them. Odfjell could not doubt provide track history since I left in 2017.
More recently I looked at completion / liner deployed solution which can use scrapers, brush or magnets (or any combination of these) which would become a permanent installation in the well. These have matched metallurgy, connections, burst, collapse and ID of the completion or liner and could be run immediately below the liner hanger / lower completion packer. The comparative price to the cost of the DrillRdillo or Switchback would be lower, but the disadvantage would be the potential inability to work the string & circulate the well clean (the limitation not being the tool itself but the liner / completion it is attached to).
So apologies for shamefully pitching my own design, however I did present 2 other options in a fair manner... and you did ask.
Hope that is of use in the discussion
Oh, one more thing.
I'm 'old school' in that if you don't absolutely need a tool in the BHA, then don't run it - it's just one more thing to potentially go wrong.
When I first started (back in the days of yore...), the company I worked for had a practice of running a scraper across the liner setting point.
Usually we did this on the pre-liner wiper trip, but then the casing design changed and we were running two liners in each Well - one of which was a drilling liner and only had one logging run in that section.
The hole condition was good, so we decided that we didn't need to do a wiper trip and when the subject of running a scraper was raised, it was one of those 'not really thought about it, we've always done it' things.
We kicked it around and since nobody really had a good reason why we couldn't drop the scraper run, we did.
Had no problems to the extent it become Company policy on all wells that a scraper runs would only be done in exceptional circumstances (similar to Peter's comments).
Since then, I've never bothered running a scraper (with the same caveats as Peter) and never had any issues.
Since then, if I've seen liner problems, it's nearly always been due to poor hole conditions or the hole not being circulated clean properly and cuttings packing off around the hanger - nothing to do with not scraping the hanger setting depth.
All the best!
I’ll Reclassify somewhat
9/10 in new wells we would not run a scraper first in certain applications eg running a plug into a well after we pulled out a bha that was stiffer in the first place.
After drilling a new well and during clean up run prior to running a completion a scraper is a standard tool.
on old wells where we intervene or work over this is a more difficult risk based decision based on wells evident history.
At at the end of the day a determined evaluative risk based operational decision must be made by those responsible for the well.
Risked based decision Dave.
9 out of 10 times we don’t do this if we don’t foresee a problem or risk.
if a well has risks scale debris is old corroded has a fish in it you have been milling etc. One makes a determined decision and may run a scraper clean out assembly first.
The problem here is that what’s going into the hole and who owns this typically states ‘ a scraper run must be performed’ no one wants to take a risk however small. Where teams and organisation run a scraper etc and generally see nothing that would impact or effect following tool being run into the hole.