After an acidizing operation, k is reduced from 20 mD to 12 mD,
but Skin is also reduced from 1 to -2.3.
Why do we see this relation between K and S?
Junior Member
After an acidizing operation, k is reduced from 20 mD to 12 mD,
but Skin is also reduced from 1 to -2.3.
Why do we see this relation between K and S?
is this gas well? k reduction can be due to reduce rel perm. Check ur match on both rate and pressure history
Junior Member
No it is exploration oil well.Originally Posted by UsmanHWU
send me post and pre PBU data at muhammad.mech@gmail.com
Saphir files will be more handy
Junior Member
good call to look at before and after. The lower k after acid-job does not make sense.
Junior Member
Why not? Maybe acid type/selection is not proper.
Active Member
k is a property of rock. It should not change. in your case i would check radius of investigation or the the quality of data.
Member
K can change if fines fill the pores or completion fluid bad reaction with reservoir fluid forming gum that plugged the pore or bacteria reacted with fluid....the list continue....
Volunteer Moderator
I think this may take place but if you take this form well test
So what you done is enhance your well bore area but not the rock near the well , or may be you harm you rock by lowing BHP at the well
are there any fractures ?
Very Active Member
Without seeing the data, or knowledge of the type of reservoir, I would guess the following;
1. Negative skin post treatment due to near wellbore enhancement from the acidizing treatment (although surprising that you got a negative skin if a clastic - did you inject above frac pressure perhaps?)
2. Decreased interpreted perm post treatment due to (I'm guessing) treatment overflush of the spent fluids deeper into the formation, damaging deeper permeability
3. Relatively short test was conducted, meaning true deep permeability was never tested in the post treatment analysis
I would further hazard a guess that if you were damaging deep perm, that you were treating a clastic formation with mud acid, and that clastic had some calcites in it, which adversely react with HF once the pH rises again - Sounds like you did not run enough HCl preflush
Actually in exploration wells - it is not uncommon to drill significantly overbalanced (for safety when pore pressures not well understood), damaging the wells in the process. When very damaged exploration wells find hydrocarbons, it is not unheard of to simply pump high strength mud-acid without any HCl preflush, and the test immediately before much of the precipitating damage can occur - before abandoning the well - This could well be what happened.
All high level supposition - Acidizing involves complex reactions, highly dependant upon your mineralogy - any number of damage mechanisms could have occurred.
Last edited by vinomarky; 11-13-2014 at 02:55 PM.
Active Member
Looks like for me initial interpretation was not right, try to match initial pressure data to the same k as after acid-job,
and please check the possible fluid viscosity chanches due to different BHFP...
Volunteer Moderator
[QUOTE=vinomarky;284722]Without seeing the data, or knowledge of the type of reservoir, I would guess the following;
1. Negative skin post treatment due to near wellbore enhancement from the acidizing treatment (although surprising that you got a negative skin if a clastic - did you inject above frac pressure perhaps?)
2. Decreased interpreted perm post treatment due to (I'm guessing) treatment overflush of the spent fluids deeper into the formation, damaging deeper permeability
3. Relatively short test was conducted, meaning true deep permeability was never tested in the post treatment analysis
I would further hazard a guess that if you were damaging deep perm, that you were treating a clastic formation with mud acid, and that clastic had some calcites in it, which adversely react with HF once the pH rises again - Sounds like you did not run enough HCl preflush
Actually in exploration wells - it is not uncommon to drill significantly overbalanced (for safety when pore pressures not well understood), damaging the wells in the process. When very damaged exploration wells find hydrocarbons, it is not unheard of to simply pump high strength mud-acid without any HCl preflush, and the test immediately before much of the precipitating damage can occur - before abandoning the well - This could well be what happened.
All high level supposition - Acidizing involves complex reactions, highly dependant upon your mineralogy - any number of damage mechanisms could have occurred.[/QUOTE
Very excessive answer, looks like the hand ( or head)) of maestro
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