Build Up and Drawdown Time estimation

[ahmedj9579]

Dear all
Please how can we estimate a build up and drawdown time estimtion for an oil well?
your reply will highly appreciate
Many thanks

[i-anuar]

ahmedj9579
you can simulate it in Pansystem and Saphire (and probably other packages). don't forget to check for WBS if you can do only surface shut in...

[ahmedj9579]

many thanks for your reply.
exactly what we need is o estimate the time for BU in order to reach boundries.
before, we did the same operation and we install gauge and record pressure (surface shut in) but after interpretation, what we notice that we didn't reach boundries?
so any help please!!!
thank you again

[i-anuar]

so you know formation properties... probably also have an idea how far boundaries are from geologist/geophysicist, likely width from thickness for this geological environment etc...

simulate how much (minimum) time you need to see it clearly on derivative. as pressure disturbance will reach boundary you will need another log cycle if it is practically possible. get few scenarios to get a range... account for a gauge type and interferences...

do you have surface readout or it is luxury? then you can stop test earlier

[ahmedj9579]

many thanks for your reply.
is it possible to rech directely ET (early time) without reaching MD(middle time : radial flow)?

because i made a simulation on saphire and what i find is a little bit strange. i can't see the radial flow and the boundary are as a close system.
should i estimate radial flow?
please advice

[i-anuar]

Depending on distance to boundaries you should see all early/mid times (unless masked by WBS). try 'shrinking box' approach moving in/closer boundaries or even adding boundaries and comparing to infinite acting system. if you will get to changing 'm' or slope before radial from WBS then you need downhole shut in i would think.
If boundaries too close than pressure will fill it quite early, try 'shrinking box'...

[i-anuar]

Depending on distance to boundaries you should see all early/mid times (unless masked by WBS). try 'shrinking box' approach moving in/closer boundaries or even adding boundaries and comparing to infinite acting system. if you will get to changing 'm' or slope before radial from WBS then you need downhole shut in i would think.
If boundaries too close than pressure will fill it quite early, try 'shrinking box'...

[darcyoil]

I am asked this question often enough, and my answer is that I cheat! What I do is two things:
1. I make my model in any PTA software and calculate time to boundary using the parameters from the initial transient testing (which we all do)
2. I go back to the initial production testing data and, from the surface records, see how long it took for pressure to stabilize (say, for example, when the well was closed for an extended period while it was being hooked up to the flow line); that way, I don't overshoot and waste time/money/downtime

I am not always right, but I do get the data for some definitive characterization most of the time