Modern acidizing

[simone.re]

Last thirty years ago, conducted the matrix acidizing in sandstone reservoir at the beginning of the reservoir life. At that time, didn't get improvement in production.
When we reviewed this acidizing programm , we've found they didn''t conduct the priliminary study of acidizing.
So, we assumed this was the improper stimulation in the past. Acidizing is the low cost compare to other stimulation technique. So I think we can get some improvement if we conduct the proper acidizing modern technique.
Please kindly share the modern acidizing technique and software and experience.

[ahmedm]

i think you mean the acidization deosnt work in sandstone usaually they conduct it for carbonates as matrix where the storage in the sands. for sands it is difficult to conduct acidizing because it is not responding to the acid as in carbonates. there is some stories of success using some solution as HF and HCL but not necessarily working for you

maybe it is better to conduct hydraulic fracturing i had an experience with sandstone reservoir where there is no way to produce naturally where the reservori is tight in permeability and other problem is swelling clay so the best way is to complete oil based mud or some chemicals instead of oil because of the economics wise and frac the well
it is producing with more than 80 wells from hydraulic fractures

i recommend fracturing instead of acidizing but make sure whats the problem maybe the clay problem or the completion


good luck brother

[am1116]

Last thirty years ago, conducted the matrix acidizing in sandstone reservoir at the beginning of the reservoir life. At that time, didn't get improvement in production.
When we reviewed this acidizing programm , we've found they didn''t conduct the priliminary study of acidizing.
So, we assumed this was the improper stimulation in the past. Acidizing is the low cost compare to other stimulation technique. So I think we can get some improvement if we conduct the proper acidizing modern technique.
Please kindly share the modern acidizing technique and software and experience.

Hi simone.re
Nice topic,however,need more explanation!
modern acidizing techniques can be found in technical papers,
And i think one of the best is SPE web site.
Today there is lots of acidizing improvement by Diverting,Retarding,Staging,..
And about app. I think at the begining we need good conceptional knowledge
of Wellperformance analysis,well testing and then reaction simulation.
so i suggest pipesim/pansys or fast or saphir/and at the end stimcade.
hope to be useful!

regards

[amin.d]

hi my pleasure is acidizing
in this paper exit nice information about acidizing that you can understanding them

[link Point to another website Only the registered members can access]

[dipak_m]

Dear Ahmedm,
I am working a company where we are dealing the reservoir which is sandstone reservoir, very tight, clay is the main problem and reservoir pressure is very low after producing 10% of OIIP. What is the best solution to produce from this reservoir.

Thanks

[Yengineer]

Dear Ahmedm,
I am working a company where we are dealing the reservoir which is sandstone reservoir, very tight, clay is the main problem and reservoir pressure is very low after producing 10% of OIIP. What is the best solution to produce from this reservoir.

Thanks

I do not think that you will achieve much (if anything) with acidizing.
Why the pressures are low? Is it because of reservoir, or because of losses?Are these well in transient flow? Do you have any decline data from other wells in this area?
Are these wells fracture stimulated? It has to be a deep reaching frac.

If reservoir has pressure, then you have to check spacing or vertical vs. horizontal. Fekete has released a new software (evolution) to help in development process.

[vinomarky]

With carbonates, acidizing works well as you are dissolving the matrix.

Sandstones are not so forgiving, as you are generally partially dissolving the damage in the siliceous matrix - relatively small pore throats to flush stuff through. It can work, and work well, but a LOT more prep work needs to be done including but not limited to;
Establishing what clays are down there (some clays you simply dont want to touch with acid)
Ensuring your acid treatment is correctly designed for the temperature and treatment time so that you don't drop precipitates too close to the critical (near wellbore) matrix

Generally, you first need to pickle the tubing and reverse out, then inject a preflush of HCL to dissolve calcites and bring the pH down (does not do much in itself, but as pH rises due to spending of acid, precipitates drop out), followed by some sort of mud-acid (HCl/HF mixture - ratio depends on temp and clay types) including appropriate inhibitors (to prevent your tubulars dissolving), clay stabilizers, chelants (aid supension of ions and delay precipitation), surfactants (to aid flowback and avoid emulsions) etc... and then an overflush to push the dissolved effluent as far out into the reservoir away from the near wellbore that you can.

The above is a real superficial flavour of some of the work you need to think about. Sandstone acidizing can be an excellent value approach, but you need to do your homework and be prepared for a learning curve.

[dipak_m]

Dear Yengineer and other members,
Thanks for you valuable responses. My reservoir is purely depletion drive reservoir, so pressure become low. Water injection started after 10 years of production but due to water injection not much pressure is jacked up. Clay is the main problem. Some wells HF was done but result is not encouriging. In some wells decline data is available.

Please name the software which Fekete has released.

Thanks

[vinomarky]

Dear Yengineer and other members,
Thanks for you valuable responses. My reservoir is purely depletion drive reservoir, so pressure become low. Water injection started after 10 years of production but due to water injection not much pressure is jacked up. Clay is the main problem. Some wells HF was done but result is not encouriging. In some wells decline data is available.

First off - please ensure that your drop in productivity is not primarily attributed to simply drop in reservoir pressure

If your reduced Pr cannot be responsible for majority of your PI reduction, then next step is figuring out what is.

With water production, you often have migrating clays - what sorts of clays do you have?
Did you do water compatibility checks on your injected water? How have your injector pressures been trending?
Would simple reperforation with big charges benefit?
Have the PI's always been poor? (ie could your understanding of your KH simply be wrong)
If your PI's have changed, has it been gradual, or abrupt? Can you link it to (for example) water breakthrough?
Could it be rel perm behaviour as your watercuts have changed?

My take is that IF you have some migrating clay fines, and IF those clay fines can be partially dissolved and/or immobilized with clay/mud acid then you may have an application for acidizing in your case - but there are a lot of if's there. There are many causes of PI reduction for which acidizing will do nothing, and quite a few scenarios in which the wrong acid job will actually ruin your well.

[dipak_m]

Dear Vinomarky
PI of my reservoir is gradually decreasing and some how may be linked with water breakthrough. Please suggest

[vinomarky]

The two prime culprits that come to mind are;

(1) Fine migrations - the water flow has mobilized previously stationary clays and brought them to the near-wellbore region

(2) Relative permeability effects in near-wellbore

If you are sure it is case (1), then there is a possibility that acid may assist, but probably not - contact your local service company and see what they have to say. Be aware that they may just want to sell you a job, so form your own opinion from what they tell you

In both cases, a little 'skin frac' - ie short fat frac may well bypass the damage, and depending upon your local provider setup, may not be too expensive - just ensure you can handle the additional water production.

Another avenue to investigate is the possibility of reperfing with big charges - depending upon how near to the wellbore the damage is residing you may well be able to bypass most of the damage with this approach - it is probably going to be cheaper than either aciszing or fraccing, and much lower risk - could be a good first step

[dipak_m]

Dear Vinomarky,
Please elaborate the procedure for 'skin frac- ie short fat frac'
Thanks