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Sodium Silicate mud
10 March 2016
I am wondering about the experiences people have with Sodium Silicate mud.

How does it effect down-hole tools?

How to calibrate hydraulic programmes?

Essentially - what are the pros and cons with such a mud system?


7 answer(s)
admin
Managing Director (rp-squared.com)
Relentless Pursuit Of Perfection Ltd.
Total Posts: 376
Join Date: 10/01/05
Hi folks

(I'm at home, temporarily confined to barracks after the birth, on 14th April, of our beautiful daughter Emma).

So, I have time to edit an excellent contribution received from a Fluids Advisor who works for a major Oil Company.

Please find attached. I have removed well names, mud weights and casing/hole sizes
Documents uploaded by user:
SILDRIL System Engineering Guidelines.pdf
JaapvdS
BDM
Compass Energy
Total Posts: 10
Join Date: 09/11/15
Most of it has been said here.
the only thing missing is how it works and where it should not be used: because the silicate reacts with Ca2+ ions (and forms this impermeable glass) it is not suitable to run in sections where you are encountering a stretch of limestone, marl anhydrite. Or at least it will be expensive to run over that stretch.
As Scott mentioned, washing down the tools with fresh water is essential otherwise you  will get the coating mentioned by gsoden and the service company will have break-out problems with its tool sub sections.
In sands and clays the hole will be gun-barrel, so POH can be tight, but the directional drillers will love it as it makes steering easy.
Then the last thing missing is HSE: This stuff is very high pH, so the drill crew and shaker hands need to be well instructed about this, and suitable PPE is more essential than ever.



Companyrep
Drilling Specialist/Well Engineer/Training Consultant
SPREADAssociates
Total Posts: 339
Join Date: 10/01/05
Chris,


As Ian pointed out I was on these rigs teams supervising that drilled three or four Explorations wells using silicate based muds offshore Norway in the 90's.
 

I remember in the planning stage we had concerns over seal, rubbers etc but we focused on this in the planning and I don't recall having that much surface or downhole issues.

Once BOP's were on, we displaced to the silicate based mud.
- hole cleaning was excellent while drilling throughout as demonstrated by cuttings quality at the shakers.

- as records will show we had few traditional problems as exhibite din these areas with WBM. On a few wells it should be said we engaged a geomechanics company to assure we were bang on target with mud wt which we know today is key to bais and essential 'MPD' i.e. make problems disappear!

- 1st trip out through a drilled section. ALWAYS appeared 'tight' in these areas drilled (dominant claystone - shale sequences ), but this was the nature of the beast and due to the fact that excellent hole quality resulted and attributed to mud properties.
So you had to take your time and pump and wipe the string out (note: these were straight wells and everyone knows my thoughts on back reaming, so we didn't do any) Pump and pull took a bit of time but no issues resulted and it was still far more expedient than the big BR!.

- Trip in as a result was like a gun barrel and any trip out through a section already tripped, generally had no further overpulls etc.

- In the smaller wellbore, particular in the 8 1/2 sections,  the silicate based mud will exhibit a MUCH HIGHER torque as lubricity is not it's selling point. So higher angle drilling would be difficult we concluded. In vertical wells (we were about 5,000m plus at TD is was all manageable)

- I also remember that in a discovery case, we had opted to change mud out to a better drill in fluid and had planned a bypass core to meet Norwegian regulatory requirements in such a case.
(well's were non commercial so we didn't need this option)

- Finally like all high end water based muds, good mud engineers with a knowledge and understanding of what's being drilled downhole and what to do to the mud real-time was a key to the success of the system. We were fortunate to have highly experienced personnel who did do a great job.  

regards,

Peter.
 

ianpetitt
(retired) Well Fluids Team leader
SPREADAssociates
Total Posts: 37
Join Date: 14/06/06
Hello Chris, Here are my comments.

Sodium Silicate was a well-known shale stabiliser and was used in mud systems in the USA in the 1930´s & 50´s.  However polymer technology was not as it is today, so parameters such as rheology and fluid loss were difficult to control in the early systems.


Silicate mud has proven over the years to be a very effective mud system for overburden intervals and is still considered by me to be the preferred High Performance Water Based Mud   system in Europe.  When formulated correctly the system will prevent pore pressure penetration occurring!    


I believe that silicate inhibit formation shales decomposition through a pH reduction process due to pore fluid contamination and/or a reaction with free cations (Ca+/Mg+). The silicate oligomers form a precipitate/gel sealing the pore space/surface of the shale. The precipitated silicate forms a physical barrier which ”œpressure isolates” the shale from the water/pressured of the drilling fluid. The mud also maintains pore pressure isolation of the shale. 


Some 10 years ago there has been good success in Norway and UK single strings, including wells on Tern , Mallard, Knave,Liverpool Bay, Kittiwake, Cormorant and many single strings wells, as well as the Pelicans development extensively.


Despite extensive testing, we never found a lubricant that worked in a silicate mud.


The system limited to about 230ºF as an operational temperature. Can be used in a reservoir but seems a strange choice.  No issue with cementing but be careful with spacers. 


Other disadvantages include gauge hole, low lubricity and hole cleaning difficulties with deviations above 30º. 


See attached picture of 17"" BHA - pretty clean! 


I remember Gary Wright an Exxon DSV being quite brilliant in running Silicate mud on Penguin wells.


The major continuing concerns are as follows:


1. Elastomer compatibility: Limited increased pump part usage on some rigs. Warn all tool suppliers, and BOP and rig companies beforehand, but this is now not such an active issue.

 

2. As you can see from comments, MWD needs to be compatible! before hand.


3. Health and Safety: not a problem although very high pH. Mud companies have skin data which shows silicate mud is non-irritating, surprisingly.

 

4. Hole cleaning: The rheology of silicate muds should be conducive to good hole cleaning, because of good shear thinning characteristics, high low end rheology and low plastic viscosity etc. So, even with high solids build up the mud often looks better than oil mud for hole cleaning.

 For high angle wells (see comments on lubricants - not recommended) where cuttings beds have been deposited, back reaming has been a problem. This has also been confirmed from other operators who also have problems with high angle long reach 12¼" sections. There are reasons for this; WBM cuttings are stickier, although not necessarily worse for silicates. But the hole is in gauge probably, so worse than for other WBM systems. Also hole cleaning procedures have not been optimised for WBMs yet. Hole tends to stay more in gauge than any other WBM system.

Also accretion or balling is more likely with WBM on the BHA.  

This can be engineered around with a bit of planning as wiper trips pumping out to 40 degree angle and then pumping clean. Heavy pills to aid hole cleaning. But it is certainly something to be aware of. 

 

5. Wellbore stability: Not an issue logged a couple of Tertiary sections and observed over gauge hole for the top 1000ft. And oval and in gauge hole for the rest of the section. Much better than we would expect from most WBMs.

We had long open hole times, on Central North Sea well of up to 50 days, and one other to 90 days with no wellbore collapse. 

 

6. ROP performance. With the correct PDC bit the ROPs can be close to OBM, but annular velocities have to be good too.


7. Did a small comparison using field data between OBM used in Central N Sea, proprietary HPWBM water based mud in Norway and low angle silicate 17 "” sections on Pelican. ROP and hours per 1000 feet very similar for OBM compared to silicate. Silicate mud costs higher but lower when cuttings transport and disposal costs taken into account.


Proprietary HPWBM much poorer and more expensive mainly due to not being able to use the full HPWBM system due to environmental regulations. 

Documents uploaded by user:
17-1:2%22 BHA_Silicate Mud.png
Scott_McNeil
Consultant
SPREADAssociates
Total Posts: 101
Join Date: 05/03/08
Hi Chris,

Was on a project a couple of years ago that successfully used Silicate mud.

Further to John's posting, as long as all the downhole tool providers (including Electric Logging) are informed well in advance, they can use the appropriate metallurgy / elastomers in their equipment.

Because we could give them lots of warning, we had no issues at all with downhole drilling tools.

There was a thought that the high failure rates we had with the Wireline sidewall coring tool could have been due to the mud system, but this was never satisfactorily proved as that particular tool had a high failure rate in other mud systems too.

One very important thing is to make sure that while downhole tools are being laid down, they are thoroughly flushed with water to get rid of the mud, otherwise it will solidify, coat everything and cost a bundle in refurb charges.

I don't recall any issues with the Rheology, although we may not have got hot enough (BHST up to about 115 Deg C) to see what John was referring to.

With respect to the Rig itself, make sure they have the right parts for the Mud Pump fluid ends.

Also, during each Rig move [or each hole section in Kurdistan ;) ], make sure all the centrifugal pumps in the mud system are opened up and the internals cleaned and checked. The impeller blades are prone to getting a build up of hardened silicate mud on them, which can significantly decrease their efficiency and also eat away at the blades.

All the best.

Scott
gsoden
Service Company Operations Manager
SPREADAssociates
Total Posts: 16
Join Date: 03/05/12
Sodium silicate mud is a nightmare for MWD tools. It coats metal surfaces, hardens rubber O rings. In not saying any more. Use at your peril.
jrsands
Consultant
Relentless Pursuit Of Perfection Ltd.
Total Posts: 4
Join Date: 15/04/13

Chris,

It is a while since I last had any dealings with silicate fluids but I guess the chemistry won't have changed all that much.

Pros:

Great for stabilising friable sands.  Sodium silicate is used as a grouting agent on big tunnelling projects and so on as it effectively becomes cement in the presence of divalent cations (Calcium & Magnesium in most drilling cases).

Best water-based inhibition of reactive shales due to the same action as above.  BP use it a lot in the Caspian in top hole with RMR as it stabilises their wet shales.

Environmentally friendly as the active ingredient becomes inert in the presence of seawater.

Cons:

The system requires large additions of silicate in wet or reactive formations.  The mud man really needs to keep on top of testing & logistics to ensure he has a decent buffer of silicate in the system.  A lot of the anecdotes about poor performance of the systems relate to silicate levels being allowed to drop.

Lubrication.  The system has no inherent lubricity.  Vegetable oil based lubes hydrolyse in the high pH environment so you would be looking at graphite or similar inert substances to get torque values down.  It wouldn't be your first choice for adventurous directional work.

Hole cleaning. You might get tight hole at mud weights that work with other WBM.  This is down to the rifle barrel silicate wellbore highlighting the real pore pressure of clays that previously sloughed away at lower mud weights.  So not really a hole cleaning issue but it certainly feels like it at surface.  You get similar issues if you try to drill reactive clays with OBM - suddenly you find out what the pore pressure of the shale really is and have to up the mud weight, which slows down ROP.

HSE. The neat silicate is very alkaline and care needs to be taken especially if you are adding from drums.  The complete mud didn't seem to give problems as the active ingredient is neutralized quickly by sweaty palms.

Cleanliness. Shaker hands aren't crazy about thin grey cement all over their workplace.  It goes away by itself eventually.  Make sure the hands don't fill the mud with untreated seawater as you will deplete the silicate faster than necessary.

Rheology.  Not necessarily a con but systems did occasionally exhibit increasing rheology with increasing temperature.  Nice & thin in the pits during tripping then getting thicker once the drilling started.  Maybe this has been addressed now?  Certainly would have an impact on your hydraulics programme inputs.

As far as downhole tools are concerned they should be fine although there were some issues very early on with super-hard elastomers (installed for POBM/EBM sections) crumbling with the silicate fluids but easily cured by going back to softer elastomers.

Someone with more recent experience will be along in a minute I'm sure.

Hope that helps

Posted by

Chris Henderson

Directional Driller

SPREADAssociates

Total Posts: 125
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