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8/13/2019 well test interpretation 2.pptx
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Lecture 02 Types of well test
*
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*In well testing, we provide input and observe
the output.
*Input is the parameter under our control
whereas, output is dependent upon system and
input
*In well testing input is a change in flow rate
and output is the pressure response
*Input may be change in production rates or
change in injection rates (if applicable)
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*Types of Well tests:
Drawdown test
Buildup test
Injection test
Fall off testDrill Stem Test
Interference test
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*Drawdown Test
In a drawdown test, we start flowing a wellthat is initially shut-in, static and stable.
The flow rate is supposed to be constant.
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Drawdown Test
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Suitable for reservoirlimits.
Traditional analysismethods aredeveloped fordrawdown tests.
Difficult to flow a wellat a constant rate.
Well conditions maynot be static or stable.
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*Buildup Test
In a buildup test, a well that is flowing
(ideally at a constant rate) is shut in and
downhole pressure measured as the
pressure builds up.
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Buildup Test
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Constant flow ratecondition is easilyachieved as the flowrate is zero.
Only slightmodification ofanalysis techniquesused for drawdownanalysis is required
Difficult to achieveconstant rateproduction prior toshut in.
Production loss whilethe well is shut in.
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*Injection Test
Similar to drawdown test except that the
flow is into the well rather than out of it.
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*
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Injection rates
are easier tocontrol thanthe productionrates.
Complicated
analysis ifmultiphaseeffects areobserved
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*Fall off test
Similar to buildup test except that
injection is stopped rather than
production. In fall off test we observe
pressure decline.
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Injection ratesare easier tocontrol.
Production loss issmall ascompared to
buildup test
Multiphaseeffects makeanalysis difficult
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*Interference Test
In an interference test, one well is
produced (or shut in) and the pressure
response is measured at another well (or
wells). Interference tests helps to
characterize the reservoir over a largerscale than the single well test.
Interference test is possible with any
type of pressure disturbance
(drawdown, buildup, injection, fall off)
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*Drill Stem Test
This test is carried over a newly drilled
well. We temporarily complete the well
and produce it for a small period of time.
Then we shut in. Again we start producing
but this second flow period is longer.Then we shut in the well again.
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*
*Modern well test analysis a computer aided
approachby Ronald N. Horne
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*
*Continued discussion regarding fundamental
concepts