Deconvolution – are you ready ?
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Take this 5-min self test in well test analysis and find out how our resources in the library can help you.
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“The force is strong with you”
Your well testing skills are excellent. Would you like to help us and contribute in order to help others to learn well test analysis ?
We will be pleased and honored to have you onboard in the Well Testing Group. Please don’t hesitate to contribute to the Well Testing Group, and if you wish, you could start a discussion, present a talk or simply talk about your experience (and we can help you with this).
We will also try to upload some challenging sessions and documents in the library so that you don’t get too bored!
Well done!
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“The force is strong with you…. but you are not a jedi yet”
Good work!
You are well versed in well test analysis, and are on your way to become an expert!
Please don’t hesitate to contribute to the Well Testing Group. If you wish, you could start a discussion, present a talk or simply talk about your experience (and we can help you with this).
We will also try to load some sessions and documents to make it challenging for you and to deepen your well testing skills.
See you then!
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Need a bit more practice!
You are on your way to learn and deepen your well testing skills.
Perhaps could we suggest to take one or two sessions in the library.
Please remember that you don’t need to be an expert to contribute to the Well Testing Group, just have a comment to make, a question to ask or a suggestion for improvement.
See you then!
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Need more practice!
In the library section under the Learning Centre, you will be able to learn a bit more about well test analysis.
We would also be happy to discuss with you any type of methods to improve your well testing skills.
We’re here to help you.Please remember that you don’t need to be an expert to contribute to the Well Testing Group, just have a comment to make, a question to ask or a suggestion for improvement.
See you then!
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- Review
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Question 1 of 14
1. Question
1 pointsLet’s start with a straightforward question:
what is a PBU test ?
Correct
easy…
Incorrect
You’ll get it right next time…
A good training session to look at in the TestWells library is called “Well Test Analysis for Novices”.
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Question 2 of 14
2. Question
1 pointsIs well test analysis only for exploration and appraisal wells ?
Correct
Indeed, a lot of information can be extracted from well test analysis on production and injection wells.
Some quick examples: We could use well test analysis on producing fields to detect water front and predict water breakthrough, detect fluid breakout and take actions before the situation becomes irreversible, calculate average reservoir pressure over time, monitor and ensure no excessive frac growth on water injectors, etc…
More on this in the Consulting and Library sections
Incorrect
A lot of information can be extracted from well test analysis on production and injection wells.
Some quick examples: We could use well test analysis on producing fields to detect water front and predict water breakthrough, detect fluid breakout before the situation becomes irreversible, calculate average reservoir pressure over time, monitor and ensure no excessive frac growth on water injectors, etc…
More on this in the Consulting and Library sections (accessible from the menu). A particular session on surveillance will be soon available in the library.
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Question 3 of 14
3. Question
1 pointsWhat is radial flow regime ?
Correct
OK, we are going to increase the difficulty level then…
Incorrect
No worries, the answers might not have been that clear.
A good training session to look at is “Well Test Analysis for Novices” in the TestWells library.
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Question 4 of 14
4. Question
1 pointsRadial flow regime in the horizontal plane is highlighted by a stabilization on the derivative. The stabilization level is:
Correct
Well done. Let’s test your skills further.
Incorrect
That’s ok, there were some few traps in the answer…
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Question 5 of 14
5. Question
2 pointsWhat type of well and reservoir could that be? (multiple choice)
(click on the plot to enlarge)
Correct
Great !
This wasn’t an easy one.
A derivative shape could represent several types of wells and reservoirs (non-uniqueness), but there are some few things that we need to consider before starting an analysis. Obviously we should know the well geometry and the type of reservoirs. We also need other sources of information, from the seismic for example.
We could also use the derivative overlay to check for some dynamic changes.
Incorrect
Too bad… perhaps you missed one answer. All the answers could have been correct here since there wasn’t sufficient information to choose one answer over the other ones.
A derivative shape could represent several types of wells and reservoirs (non-uniqueness), but there are some few things that we need to consider before starting an analysis. Obviously we should know the well geometry and the type of reservoirs. We also need other sources of information, from the seismic for example.
We could also use the derivative overlay to check for some dynamic changes.
A well testing course will be available in the library section.
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Question 6 of 14
6. Question
2 pointsWhat type of derivative response should we expect for this hydraulically fractured producer in this reservoir configuration (top view)?
(hint: permeability in the reservoir is not that high)
Correct
OK so far, so good…
What if the well was a water injector in an oil region? any issue related to this ….? any features expected on the plot?
Perhaps we could see a water/oil interface moving away from the well, and then a cold water front…
Incorrect
OK, my mistake: there were some few assumptions in this question.
For example, we assumed that the fracture wasn’t too damaged and that the channel (or the two parallel boundaries) was asymmetric enough to first feel the nearest fault.
and that we had a great pressure gauge of course…
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Question 7 of 14
7. Question
2 pointsCan we see any boundary in this conventional derivative plot below for this particular shut-in period ?
(click on the plot to enlarge)Correct
Indeed, we need more information. We need to have a look at the other well testing tools (deconvolution, superposition and the entire simulation plot).
Incorrect
In fact, there is not enough information from the conventional derivative only. We need to have a look at the overlay on the superposition plot, at the entire simulation and at deconvolution.
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Question 8 of 14
8. Question
2 pointsOk so we needed more information in the previous question. So here it is (at no cost…):
Conventional and deconvolved derivative plot:
(click on the plot to enlarge)
(We assume that a reliable deconvolved response has been derived)
Can we detect any boundary ?
Correct
Well done.
Is the discrepancy between the conventional and deconvolved derivative well understood? Otherwise have a look at the library for more info.
Incorrect
Deconvolution clearly shows the presence of boundaries, and in this case two boundaries.
This is also supported by the superposition plot and the data plot showing the simulation for the entire test. However these two tools are not necessary here, since deconvolution drives the analysis.
We recommend to have a look at some few presentations in the library.
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Question 9 of 14
9. Question
1 pointsCould you derive a reliable deconvolved response with only one PBU test ?
Correct
We need at least two shut-in periods to ensure validity of the deconvolved response and refine initial pressure.
Would we dare testing you on the limitations of deconvolution?
Incorrect
Well, even if you have an estimate of initial pressure and one shut-in period, you could derive a deconvolved response. But it might not be valid.
Please note that some few slight changes in initial pressure could change the deconvolution shape.
You need to make sure that a reliable and valid deconvolved response is derived by using 2 PBU tests. And you will be able to refine initial pressure as well.
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Question 10 of 14
10. Question
2 pointsWhat is the 2nd PBU on the conventional derivative plot showing ?
(click on the plot to enlarge)
Correct
Well done.
All the other answers could have been correct if the 2nd PBU were the green response.
Incorrect
There is an error in the rate data, which tends to vertically shift the derivative data.
All the other answers could have been correct if the 2nd PBU were the green response.
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Question 11 of 14
11. Question
1 pointsIs P* equal to the average reservoir pressure in a closed reservoir ?
Correct
Good job.
P* is a simple extrapolation of the radial flow straight line on a superposition plot. It is a rigorous calculation of the initial pressure for an isolated well with limited production in a reservoir of infinite extent. For a long term production in a reservoir of multiple production and injection wells, the evolution of P* over time would represent the evolution of average reservoir pressure around a well (under some big assumptions). In any case, P* is not an average reservoir pressure.
More info on this in the library.
Incorrect
P* is a simple extrapolation of the radial flow straight line on a superposition plot. It is a rigorous calculation of the initial pressure for an isolated well with limited production in a reservoir of infinite extent. For a long term production in a reservoir of multiple production and injection wells, the evolution of P* over time would represent the evolution of average reservoir pressure around a well (under some big assumptions). In any case, P* is not an average reservoir pressure.
More info on this in the library.
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Question 12 of 14
12. Question
1 pointsWhy do we use a downhole shut-in in exploration and appraisal wells? (multiple choice)
Correct
Well done.
So why don’t we use downhole shut-in on production wells then?
Incorrect
A downhole shut-in valve will help to minimize the wellbore volume and fluid compressibility, therefore minimize the wellbore storage coefficient.
This will give a better change to spot radial flow regime (which could be masked by wellbore storage in case of a surface shut-in).
Also gas concentration should be less below the shut-in valve, and there is less chance to have the data corrupted by wellbore phase redistribution. (but still)
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Question 13 of 14
13. Question
1 pointsWhat is the main problem with wellbore phase redistribution at shut-in?
Correct
Well done.
While it could happen to all types of producers (even dry gas wells due to condensed water), one of the main problems is the change of fluid weight below gauge over time. Then pressure at the gauge won’t be a direct measurement of the pressure at perforations.
Incorrect
While it could happen to all types of producers (even dry gas wells due to condensed water) and wellbore storage may change, one of the main problems is the change of fluid weight below the gauge over time. As a result, pressure at the gauge won’t be a direct measurement of the pressure at perforations. It is especially challenging to detect when a gas/liquid interface moves down the well (and below the gauge), as liquid gets reinjected in the reservoir.
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Question 14 of 14
14. Question
1 pointsAfter drilling and testing a vertical pilot hole (dashed pink response), a horizontal well section is completed and the new well tested (derivative in red and DP plot in dark blue)
How is the well performance of the horizontal well compared to the vertical well?
(click on the plot to enlarge)
Correct
Indeed.
In fact a lot of information could be obtained just by looking at a derivative overlay, without doing any analysis.
Incorrect
A lot of information could be obtained just by looking at a derivative overlay, without doing any analysis.
Some few presentations will be available in the learning centre to help you with this.
