Well Integrity Technical Section

Background:
With today's planned well path with 60 deg in the injection zone and 40-50 m 8 ½" rat hole, it is unlikely that we will be able to get a particularly large amount of gravel into the rat hole during gravel packing. There is great uncertainty as to whether gravel will fall into the rat hole after the gravel pack job, and thus deteriorate the gravel pack in the lower part.

Question: Do we have good experience about a rathole eliminator set at behind the bit when we drill ? After drilling to TD, we can open rat holes to 9 ½" via underreamer. Question is to how to eliminate rathole as much as possible?

Thanks in advance;
Kind Regards,
Aminul Islam
SPE - member



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Hi Aminul,
There is good industry experience with rathole eliminators but you'll likely have a good ten meters of rathole left. You're likely running an RSS above the bit and maybe some drilling mechanics sub hence you'll end up with the underreamer cutters some way back. If you run a motor on top of the RSS you'll add another couple of meters, unless you want to rotate the rathole eliminator all along the tangent. The only way to eliminate the rathole is a dedicated run with a bullnose and the underreamer above it.
If you are pretty certain about the reservoir and where you want to go, and you don't need LWD, you could try a bi-center bit. Depening on the rathole formation, you might want to consider liner drilling, either with a disposible motor or simply by rotating the liner. I guess you are running screens that are somewhat fragile hence rotation might not be possible but disposible motors are a good option (4 3/4 in. made up to the lower completion).
LWD just had me thinking, you may need the rathole if you want to get your sensor across the entire reservoir to determine top and bottom. Might be another reason why you won't be able to get rig of the rathole...
Thinking out load, you could run a slimmer stinger into the rathole; 4 1/2 vs. 6 in. liner/screens or simply run some sort of packer at the bottom of the screens and simply isolate the rathole from the rest of the well.
You could also drill the rathole and then simply fill it with a sand plug on the way out.
There are different options that don't need to involve drilling.
All of this depends on your formation, is there water in the base that you want to avoid, are you producing gas and don't want to enter the oil leg, is it a long well and a dedicated trip takes forever, are there pore and frac pressure restraints that making tripping a challenge and you need to avoid them as much as possible, are there wellbore stability concerns, time-sensitive formations (wellbore stability), maybe you'd be better off having a dedicated drilling run for formation evaluation followed by a dedicated hole opening run, can you change the rest of the well design to allow for a larger hole, do you need a 9 1/2 in., how thick is the reservoir (can you live with less), what about other completion design (expandable screens, smaller liner, use a slotted or preperforated liner that you expand against the formation and then run screens inside it, etc.), what are the constraints?
You can there are options other than drilling.
Great if you could share more information.

Thanks,

Matthias

Hi Matthias and Ron Nelson;

Thank you for providing details insight info about the subject topic. We are still under method selection phase and considering different methods.
We may consider using the TDReam to reduce the length of the 8 ½" rat hole after we have underreamed the reservoir section to 9 ½".

If anyone having a good experience on this TDReam method, It will be appreciated to discuss the following points:


* Will a TDReam in the BHA have an impact on the selection of the RSS or other components in the BHA?
* Has any DLS limitation with the TDReam in the String?
* Which activation methods could be best/challenges
* Is there any other technical limitations/challenges related to using the TDReam to reduce the length of the rathole?

The reservoir section length is approx. 770 m, also coal fms are there.

Kind Regards,
Aminul




-------------------------------------------------------------------
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorized use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you


Original Message:
Sent: 10/21/2022 9:24:00 AM
From: Matthias Kirchhoff
Subject: RE: Rat Hole Eliminator

Hi Aminul,
There is good industry experience with rathole eliminators but you'll likely have a good ten meters of rathole left. You're likely running an RSS above the bit and maybe some drilling mechanics sub hence you'll end up with the underreamer cutters some way back. If you run a motor on top of the RSS you'll add another couple of meters, unless you want to rotate the rathole eliminator all along the tangent. The only way to eliminate the rathole is a dedicated run with a bullnose and the underreamer above it.
If you are pretty certain about the reservoir and where you want to go, and you don't need LWD, you could try a bi-center bit. Depening on the rathole formation, you might want to consider liner drilling, either with a disposible motor or simply by rotating the liner. I guess you are running screens that are somewhat fragile hence rotation might not be possible but disposible motors are a good option (4 3/4 in. made up to the lower completion).
LWD just had me thinking, you may need the rathole if you want to get your sensor across the entire reservoir to determine top and bottom. Might be another reason why you won't be able to get rig of the rathole...
Thinking out load, you could run a slimmer stinger into the rathole; 4 1/2 vs. 6 in. liner/screens or simply run some sort of packer at the bottom of the screens and simply isolate the rathole from the rest of the well.
You could also drill the rathole and then simply fill it with a sand plug on the way out.
There are different options that don't need to involve drilling.
All of this depends on your formation, is there water in the base that you want to avoid, are you producing gas and don't want to enter the oil leg, is it a long well and a dedicated trip takes forever, are there pore and frac pressure restraints that making tripping a challenge and you need to avoid them as much as possible, are there wellbore stability concerns, time-sensitive formations (wellbore stability), maybe you'd be better off having a dedicated drilling run for formation evaluation followed by a dedicated hole opening run, can you change the rest of the well design to allow for a larger hole, do you need a 9 1/2 in., how thick is the reservoir (can you live with less), what about other completion design (expandable screens, smaller liner, use a slotted or preperforated liner that you expand against the formation and then run screens inside it, etc.), what are the constraints?
You can there are options other than drilling.
Great if you could share more information.

Thanks,

Matthias

Aminul,

Can you send us the details of the TDReam? Who makes it?
As far as I am aware, any rathole underreamer definitely goes above the RSS and possibly above the motor, if you run one. You'd also have to selct it carefully to have a passthrough for your electronics connection from the MWD to the RSS.

Matthias
Original Message:
Sent: 10-24-2022 10:54 AM
From: Md Islam
Subject: Rat Hole Eliminator

Hi Matthias and Ron Nelson;

Thank you for providing details insight info about the subject topic. We are still under method selection phase and considering different methods.
We may consider using the TDReam to reduce the length of the 8 ½" rat hole after we have underreamed the reservoir section to 9 ½".

If anyone having a good experience on this TDReam method, It will be appreciated to discuss the following points:


* Will a TDReam in the BHA have an impact on the selection of the RSS or other components in the BHA?
* Has any DLS limitation with the TDReam in the String?
* Which activation methods could be best/challenges
* Is there any other technical limitations/challenges related to using the TDReam to reduce the length of the rathole?

The reservoir section length is approx. 770 m, also coal fms are there.

Kind Regards,
Aminul




-------------------------------------------------------------------
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorized use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you



Original Message:
Sent: 10/21/2022 9:24:00 AM
From: Matthias Kirchhoff
Subject: RE: Rat Hole Eliminator

Hi Aminul,
There is good industry experience with rathole eliminators but you'll likely have a good ten meters of rathole left. You're likely running an RSS above the bit and maybe some drilling mechanics sub hence you'll end up with the underreamer cutters some way back. If you run a motor on top of the RSS you'll add another couple of meters, unless you want to rotate the rathole eliminator all along the tangent. The only way to eliminate the rathole is a dedicated run with a bullnose and the underreamer above it.
If you are pretty certain about the reservoir and where you want to go, and you don't need LWD, you could try a bi-center bit. Depening on the rathole formation, you might want to consider liner drilling, either with a disposible motor or simply by rotating the liner. I guess you are running screens that are somewhat fragile hence rotation might not be possible but disposible motors are a good option (4 3/4 in. made up to the lower completion).
LWD just had me thinking, you may need the rathole if you want to get your sensor across the entire reservoir to determine top and bottom. Might be another reason why you won't be able to get rig of the rathole...
Thinking out load, you could run a slimmer stinger into the rathole; 4 1/2 vs. 6 in. liner/screens or simply run some sort of packer at the bottom of the screens and simply isolate the rathole from the rest of the well.
You could also drill the rathole and then simply fill it with a sand plug on the way out.
There are different options that don't need to involve drilling.
All of this depends on your formation, is there water in the base that you want to avoid, are you producing gas and don't want to enter the oil leg, is it a long well and a dedicated trip takes forever, are there pore and frac pressure restraints that making tripping a challenge and you need to avoid them as much as possible, are there wellbore stability concerns, time-sensitive formations (wellbore stability), maybe you'd be better off having a dedicated drilling run for formation evaluation followed by a dedicated hole opening run, can you change the rest of the well design to allow for a larger hole, do you need a 9 1/2 in., how thick is the reservoir (can you live with less), what about other completion design (expandable screens, smaller liner, use a slotted or preperforated liner that you expand against the formation and then run screens inside it, etc.), what are the constraints?
You can there are options other than drilling.
Great if you could share more information.

Thanks,

Matthias

Hi Matthias;

Thanks again for providing your feedback.

Please see the link below which presents TDReam:

LINK<https: www.halliburton.com/en/products/tdream-hole-enlargement-tool="">

Kind Regards,
Aminul


-------------------------------------------------------------------
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorized use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you


Original Message:
Sent: 10/24/2022 12:21:00 PM
From: Matthias Kirchhoff
Subject: RE: Rat Hole Eliminator

Aminul,

Can you send us the details of the TDReam? Who makes it?
As far as I am aware, any rathole underreamer definitely goes above the RSS and possibly above the motor, if you run one. You'd also have to selct it carefully to have a passthrough for your electronics connection from the MWD to the RSS.

Matthias

Original Message:
Sent: 10-24-2022 10:54 AM
From: Md Islam
Subject: Rat Hole Eliminator

Hi Matthias and Ron Nelson;

Thank you for providing details insight info about the subject topic. We are still under method selection phase and considering different methods.
We may consider using the TDReam to reduce the length of the 8 ½" rat hole after we have underreamed the reservoir section to 9 ½".

If anyone having a good experience on this TDReam method, It will be appreciated to discuss the following points:


* Will a TDReam in the BHA have an impact on the selection of the RSS or other components in the BHA?
* Has any DLS limitation with the TDReam in the String?
* Which activation methods could be best/challenges
* Is there any other technical limitations/challenges related to using the TDReam to reduce the length of the rathole?

The reservoir section length is approx. 770 m, also coal fms are there.

Kind Regards,
Aminul




-------------------------------------------------------------------
The information contained in this message may be CONFIDENTIAL and is
intended for the addressee only. Any unauthorized use, dissemination of the
information or copying of this message is prohibited. If you are not the
addressee, please notify the sender immediately by return e-mail and delete
this message.
Thank you

Forgive me if I'm missing some of the well's complexity here Aminul, but two possible solutions leap to mind.  One would be a mechanically set open hole packer on the base on screen, with a solid bottom or wash down check on the base.  This would isolate the rathole and provide a foundation for the gravel.  

Alternatively, can you not run screen to TD and circulate the gravel in place by running wash pipe to the base of screens?  That screen length below the reservoir is wasted but I agree that a 60 deg hole angle is problematic and that the annular pack could migrate into the sump, if not packed.  

Good luck with your well,
Ron

------------------------------
Ron Nelson
Subsea Completion Consultant
ron@deep-blue.ca
------------------------------