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🔴Key of question from 17th may onwards🔴 B C B B B A

Now, here in isochronal test, there was one minor limit of this approach, that is, in this different buildups period were kept till the stablised reservr pressure was reached. So at last we did one modification in Isochronal that we were starting flow period without letting the buildup period reservoir press to stabilise. i.e. In this, buildup and drawdown period were kept fixed independently, without letting any pressure to stablise either in buildup or drawdown period. This test reduced the time of test than the isochronal test. This is applicable in low to very low permeability formation aka MODIFIED ISOCHRONAL TEST.

Guys it's very simple sometime when flow and pressure follows a quadratic or exponential relations, then we require 2 or more equations to get the right solution as we do in maths, more the unknown parameters more equations will be required. Now, initially we were using flow after flow test. In FAF test a fixed flowrate is maintained until a stablised flow pressure is acheived. One more important thing is that, time to reach stablisation is inversely prop to permeability. Now, for high permeability reserv. Time to reach stablisation pr was less. And flow after flow used to be completed in lesser time. Now when the perm is less then time to stablisation press increases and hence it becomes time consuming to use FAF test. So we started a new approch that is ISOCHRONAL (drawdown+buildup) test... From it's name itself, its iso+chronal=equal time of flow yest. Here, flow times are equal, irrespective of wheather the stablised flow pr is reached or not BUT, buildup continues until the stablised reser pr is reached..., Due to equal small interval flow times the overall test time is reduced and hence it consumes lesser time. That's why isochronal test is used preferebly in low perm reservoirs, where FAF takes large time to complete.. Hope u understand.

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