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Does Fracseal cause Formation damage?
14 December 2018
Dear colleagues

At a recent DWOP, we were discussing the pros and cons of Fracseal.  

The team have found this product to be most excellent at pro-actively preventing losses (plus many other advantages), but we're now wanting to be sure that it is non-damaging.

We plan to test it against sidewall core.

What experience does our membership have of this and what advice would you offer?

C'mon you lot!  2750 members and less than 10% of you are "active"!  Ask yourself: have I contributed at least one question or one response in the past year?  If you are reluctant/don't-know-how, contact me and I will guide you.

Cheers

Dave
4 answer(s)
GiancarloPia
HPHT Project Manager
OMV
Total Posts: 1
Join Date: 13/12/18

I think Ruari defines the dilemma well.

I am intending using FracSeal as background LCM in my upcoming HPHT well on 2 separate hole sections:

  1. top of a long large diameter hole section to give me increased LOT to drill into our pressure ramp, and
  2. Minimise risks of losses in our 12 1/4" section in a known losses zone.

So what are we doing?

  1. Using the vastly superior knowledge and experience of our captive global fluids expert to test our OBM and WBM systems thoroughly and supervise our reverse perm tests.
  2. Use our extensive core lab to do reverse perm tests on relevant offset cores from close offset wells
  3. Use our fluids provider mud lab to ensure we have both our WBM and OBM systems correct as we will use a 2.1sg WBM so need to ensure we have mitigated our barite drop out. Same for our 2.2 - 2.3sg OBM systems

Happily both are overburden formations but since the same OBM with Fracseal in since previous section will be used to drill our reservoir section below, we need to be sure.

So my thoughts are:

  1. Have an agreed testing programme with your fluids specialist ( not your fluids company) months in advance and ensure you get your final recipe samples to the Lab months in advance so we have the mix agreed with time to tweak
  2. Use an experienced fluids specialist - drilling engineers are not mud engineers otherwise they would be working as one....! The Chemistry is complex and it needs focus and experience
  3. Make sure you have the best offset cores you can get and do your reverse perm tests with your final recipe to system pressures, (eliminating claims of the additive caused damage instead of a tight reservoir!) - get as close to reality as you can.
  4. Avoid making decisions on the fly, get your decision trees and risk matrix done before the well spuds.
RuariTruter
Norwell Engineering
Total Posts: 23
Join Date: 17/09/07
In my experience, however time consuming, you have to do some testing/throw some science at it (As per Tim/Ritthy).

Twice, in my direct experience, we pumped a 'non-damaging' product. Everyone swore blind it was non-damaging, it was miraculous, never had a problem, the salesman had spec sheets with "Quotes from real people", and the team had boiled it up in the galley with the  cuttings and it looked fine.  To this day, both wells are limping along, after full intervention, at ~ΒΌ of the rest.  Neither was Fracseal, and both were pumped at short notice after being deployed at short notice (A lesson in itself).

It needs reviewed by someone with the correct experience in fluids and formation damage, and tests need to be either carried out or existing tests verified for applicability.

Cheers...Ruari
TimEldred
Fluids Specialist
Medco Energi
Total Posts: 2
Join Date: 21/03/19
Ok, so this a very broad question. 
Each reservoir has its own characteristics, what may be damaging to one reservoir may not be to another.

The only true way to determine if the Fracseal is reservoir damaging (as is mentioned above) is to conduct return permeability testing with either actual core from the reservoir being drilled, or a standardized core plug that closely matches the reservoir characteristics (Pore throat diameter / permeability etc).

In the case of Fracseal, I may be wrong but I believe it consists of cellulose fibers. Cellulose is temperature degradable. Given its particle size, it generally only forms part of the filter cake with little or no invasion into the deeper well-bore. Lift off pressure and Depth of penetration into the core of the fracseal and other solids / fluids can be determined by the analysis of the return perm study results. Including Scanning Electron Microscope.

Cheers,
Tim


rson
Drilling Engineer
SM Energy
Total Posts: 4
Join Date: 01/10/18
Dave,

This might be going off into the weeds, but published work on field and lab testing of formation damage effects on injectivity of injection wells should prove useful.

Injectivity tests on the sidewall core with the planned drilling mud (with and without Fracseal) will provide you with a baseline and altered permeability ratio vs core effulent plot which will be useful in characterizing the extent of the formation damage. Backflushing (reverse flow through the same core) and the resulting perm ratio will give you a good idea on the skin damage "post production".

A similar process is detailed in SPE 39487 (Nasr-El-Din, 1998) on restoring the injectivity of waste water disposal wells - See Fig 5.

Nasr-El Din along with other workers have provided guidance on core length/size and preparation methods to minimize negative lab/core preparation effects on the results as well.

Core Flooding as Related to Water Injection (Heriot-Watt University, 1999)

You may also consider the particle size distribution (in microns) of the Fracseal and the pore throat sizing of the target formation. Pore throat plugging which contributes to the formation damage may also occur if there is a significant distribution of the Fracseal particles smaller than the pore throats.

Any natural fracturing of the formation may also complicate the analysis - the Heriot Watt reference does provide a method to consider this in the lab testing.
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Relentless Pursuit Of Perfection Ltd.

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