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Technical Discussions
Magnus
Magnus
12:38 Mar-26-2009
Casing collar locator: UT or MFL

Hi!
I am currently working on my bachelor thesis and I have a question regarding an NDT-technique:
In an oil well you first drill out a length of rock. Then you case this hole with steel-piping. The steel pipes are 12 meters long and connected by a connection. The connection is ca. 1 ft and has inner threads. The ends of the casing pipes has outer threads. So in general the casing connector appears every 12th meter with an increase in thickness of ca. 1 inch.
While you are drilling a well, the well is usually filled up with a water- or oil based mud, that in general is just a liquid phase with minerals added. Assume that the casing is placed in the well, and the mud is in the casing.

I want a brainstorm regarding the best way to easily detect these casing connectors if you are able to lower something down the inside the pipe.
I want the crowd to be inventive and suggest whatever pops up in their head.

Regards
Magnus

    
 
 Reply 
 
R. Duwe
NDT Inspector, API-510, 570, 653
MISTRAS, USA, Joined Jan 2009, 148

R. Duwe

NDT Inspector, API-510, 570, 653
MISTRAS,
USA,
Joined Jan 2009
148
16:37 Mar-26-2009
Re: Casing collar locator: UT or MFL
In Reply to Magnus at 12:38 Mar-26-2009 (Opening).

Magnus, if your casing is only thickened on the female coupling - bell & socket - then downhole UT will only see the decrease in thickness of the male thread portion of the casing. Additionally, unless the threads are a flat-bottom profile, like ACME, there will me a major loss of reflected energy, probably a complete loss of backwall reflection. The sound beam will be bounced back & forth in the 60 degree [or so] thread angle, and never reflect back to the transducer. UT would be a poor choice, I believe.

I'm thinking MFL or eddy-current, but not very knowledgable in either. Sorry.

    
 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 298

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
298
17:13 Mar-26-2009
Re: Casing collar locator: UT or MFL
In Reply to R. Duwe at 16:37 Mar-26-2009 .

Magnus,
Further to R. Duwe's reply, this may give you the information that you need.
Scan down the tube until the Back-wall echo significantly drops cause by the threads.
A fairly low frequency immersion probe (perhaps 1 to 2.5 MHz) set to radiate radially into the pipe from the bore, and guided perpendicular to the bore within about 3 to 5 degrees, and spaced a constant distance from the bore should provide the information that you need.

Regards,
Godfrey

    
 
 Reply 
 
Andreas
NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh, Germany, Joined Oct 1999, 128

Andreas

NDT Inspector, Specially in the oilfield
Tuboscope Vetco(Deutschland)Gmbh,
Germany,
Joined Oct 1999
128
23:52 Mar-26-2009
Re: Casing collar locator: UT or MFL
In Reply to Magnus at 12:38 Mar-26-2009 (Opening).

To my knowledge logging company like Schlumberger etc using MFL & EC for this purpose.US would be the wrong choice.
Anyway these days all oil company use a tally when running casing in the hole.

Andreas

    
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
10:40 Mar-27-2009
Re: Casing collar locator: UT or MFL
In Reply to Godfrey Hands at 17:13 Mar-26-2009 .

Dear Sir,

I agree with you on the method suggested. I got similar idea when I first saw the post.

Where I thought differently is about the back wall echo. I presumed the collar is also of steel or at least cast iron. Also the tube is filled with water or mixture of oil and mud. This mixture (mostly the oil or water component) percolates into the thread portion between the steel tube and collar thus facilitating ultrasonic coupling. At least this must be true for about 2 to 3 inches at the middle of the collar where the steel pipe ends are joining. (The oil/water percolates through the joint)

In this case the beam need not stop at the threaded portion of the pipe but travels into the coupling/collar. Then a clear cut back wall from the coupling should be seen after the interfering echoes from the threads. The rest is simple.

If this works, then the probe need not be maintained at a constant distance from the pipe which task becomes difficult when the depth is increasing. If large depths are involved I suggest that a preamplifier should be integrated with the probe.

P V SASTRY

    
 
 Reply 
 
John O'Brien
Consultant, -
Chevron ETC , USA, Joined Jan 2000, 278

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
11:26 Mar-28-2009
Re: Casing collar locator: UT or MFL
In Reply to Andreas at 23:52 Mar-26-2009 .

The posts to date are generally correct - you are really looking at the wrong Forum you should pursue the downhole sector. Schlumberger, Weatherford, Halliburton etc are all master sin this area and there are many tools for doing what is suggested. The thesis might best be targeted at how effective these tools are, what they detect, what they miss and what are the challenges.

    
 
 Reply 
 
Magnus
Magnus
12:49 Mar-30-2009
Re: Casing collar locator: UT or MFL
In Reply to John O'Brien at 11:26 Mar-28-2009 .

Dear sirs.
Thank you for showing interest to my question.

Ok, my turn to defend myself a little bit.
I know there are technical detectors to detect casing collars. And I know Schlumberger is the #1 logging company in the oil industry and what they use I don't know.
I'm writing my thesis with Weatherford and the question I was given was: What is the easiest and best way to detect a casing collar in combination with a well-intervention operation.
Well interventions are operations made on a mature well, where you lower down equipment to make new holes etc. Do those not very known in the oil industry all operations are best made as cost effective as possible and the best way to do this is "one trip". These are operations where the string, where equipment are placed in the end, are only lowered and raised in the well once.

So to sum it up.
Example: We have a mature oil well that we have killed with heavy mud. We are about to lower a string of pipe-sections with some kind of tool in the end through the inside of the casing. We know the depth where we are going to do the operation, but we don't want to hit the pipe connections that are characterized by being a section of thicker metall, so the last +- 2 ft we have to determe when we reach the depth.
What could we implement in the end-area of the string that easily detects the collars as the string is lowered? Assume this is the only task is has to do.

I know many of you has given the answer but I just want everyone to understand how simple I want this to be.

Regards

Magnus

    
 
 Reply 
 
TomNelligan
Engineering,
retired, USA, Joined Nov 1998, 390

TomNelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
20:35 Mar-31-2009
Re: Casing collar locator: UT or MFL
In Reply to Magnus at 12:49 Mar-30-2009 .

I believe that you will find that the drill mud is highly scattering at typical ultrasonic test frequencies in the megahertz range, so what would be a fairly straightforward pulse/echo test if the casing was filled with clean water will be more difficult in this case due to signal losses in the mud. We've sold equipment to researchers who were looking at sound velocity in various muds and slurries, and the path loss is many times higher than in water, in some cases requiring through transmission testing at frequencies below 500 KHz.

    
 
 Reply 
 
Sid
Sid
10:06 Oct-11-2013
Re: Casing collar locator: UT or MFL
In Reply to Magnus at 12:38 Mar-26-2009 (Opening).

Hello Magnus,

I read your post today and I would be very interested to know about your solution to the problem you asked in the forum. I am new to this field and I am trying to find the best possible solution in locating collars in a cased well as a part of my internship. I would be glad if you help me out in this regard.

Thank you

    
 
 Reply 
 
David Baeley
Engineering,
Australia, Joined Dec 2014, 17

David Baeley

Engineering,
Australia,
Joined Dec 2014
17
11:46 Feb-05-2015
Re: Casing collar locator: UT or MFL
In Reply to Magnus at 12:38 Mar-26-2009 (Opening).

I suggest you can read suitable article regarding drilling tools and equipments on internet.

    
 
 Reply 
 

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