Problem 2. A well is centered in an isolated, homogeneous, cylindrical 9 ft thick reservoir of unknown radius. Formation* Reservoir compressibility is expected to be 1E-5/psi, average porosity is 20%, and the formation shrinkage factor (calculated from test well production) is roughly 0.83 STB/bbl. The well flows pseudosteady-state at 10 STB/day for two whole days over which time the reservoir pressure falls a surprising 3 psi. The best estimate of reservoir radius (ft) to report to your company is: (A) 300 (B) 600 (C) 900 (D) 1,200.
This type of problem is in the Guidebook on 12 WLT 3. For this particular example the numbers are adjusted in such a way the answer remains 900 ft. But it's a tough calculation to to in a hurry, so be careful. Although this example is fairly "plug-and-chug" the challenge is to recognize the problem type and solution method fast enough to finish out the calculations quickly. The key word is pseudosteady-state, and a quick overview of the Guidebook cover brings you to the right equation quickly.
*typo.
For this one, I used the first equation on 12 WLT 3 and solved for Vb, or re. Is this the right way? I got kind of close, but ended up with 741, so ended up picking B, because it was closer. Am I on the right track here?
ReplyDeleteNevermind--figured out I forgot to convert the shrinkage factor to B. You had that on another problem on 2018 that I caught myself using wrong at first. Trick tricky! Got 893 now. Thanks
ReplyDeleteI agree on the tricky part.
DeleteThe way this exam is hard is misdirection. But once you've seen enough examples, you've got the game by the tail. Don't let it get to you, just keep on going until you've seen eough :-).
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ReplyDeleteDavid, thanks for all the help. But what would happen if one tries to solve this problem using only the Reference Guide that will be provided during this year's exam? I'm having this same issue on virtually all of the calculation problems. I understand them using your Guidebook, but am unable to solve them using only the Reference Guide. Could you explain what equation you would use from the 2019 Reference Guide so that I may understand? For this one, I found a similar equation on page 15 of the Reference Guide, but do not have enough information to solve it.
ReplyDeletePaul, remember that equation comes out of SPE Volume #1. Regardless of if it's included in the referenced text, one should at least have familiarity with it and the concepts.
DeleteLook, as somebody who has taken this exam and talked with dozens who have done so, it's not a plug-and-chug exam. And I strongly doubt it will become one with the new reference. Just try to understand the concepts, and do problems using the new reference with all the SPE texts and Guidebook, and you will get enough understanding to remember enough to compete on the exam. Remember, you will only have the reference, but they aren't bound by this at all. They can include equations in their problems or just ask broad word problems. Note my practice problems have tons of word questions to address this. Also, the Guidebook is designed to give an "overview" or "memory aid" to help remember the boundaries of you knowledge, not so much a plug-and-chug device. I believe the new exam will also have pass rates inversely proportional to how often one uses the provided reference.
Thank you for these practice questions. I am enjoying the challenge but having trouble using the 2019 Guidebook.
ReplyDeleteI'm having trouble finding the equations in the 2019 Guidebook to solve the 2018 Practice Exam calculation problems. In fact, I spent almost 30 minutes trying to find an equation for one problem alone! The only calculation problems I got right were drilling problems because I'm a drilling engineer and knew the equation off the top of my head. I watched 60 hours of lectures from School of PE and am somewhat confident in the concepts but finding the equations is driving me crazy.
I deliberately made the 2018 Practice Problems have a few questions that could not be found in the Guidebook. The Guidebook simply cannot have everything that could be asked on the PE exam (I am thinking my notes had maybe 80% of what I saw on the exam when I took it, and those notes became the GB).
DeleteEven when I took the exam, I used my notes to "center" my thinking and "guide" me during the exam. It mattered more as a mental structure to study from rather than an equation list. You really need to "know" how to do the problems more than try to look them up in what is now the provided resource. Just knowing when to "ditch" a problem you aren't familiar with is really important to passing the exam. You won't get them all. Read my blog posts on this issue for more details.
Keep in mind you will know a lot even without notes, so 80% overlap is actually really close to 100%. Each engineer has a different set of what he knows and doesn't even need to look up at all. You would't believe how much difference there is between engineers in subjects the know and know nothing about. I had engineers tell me how hard RE or Drilling or Prod or WF or logging was on the exam I took, and honestly didn't even remember questions with that info. Why? Because I knew them and just moved on, not even thinking they are the "problem" but rather just a offhand detail. Remember you can have A, B, C, D and each one can have a separate word problem item that you may just blow through.
DeleteThank you for your reply. I appreciate your help!
ReplyDeleteFor anyone curious how to use the SPE Reference Guide.
ReplyDelete2020 version. Page 16. Reservoir Pore Volume. Solve for Vp. Convert shrinkage factor to Bo; SF = 1/Bo
Pg 5 shows that Vp= A*h*porosity. A = pi * r^2. Solve for r.
Answer is 891 or C
Thank you!
DeleteHow did you convert formatiom compressibility, as given in the problem, into total compressibility, as required for use of the formula on pg. 16. The partial derivative of the pressure decline, for verification, is (-3/2), correct?
DeleteWow, that "formation" should be "total" in the problem. Nice catch. I thought that had been fixed, but looking at the actual exam it isn't. Thanks!
DeleteLooks like that "Formation" to "Total" still hasn't been fixed.
DeleteWhat value do we use for the partial d(P)/d(t) in the Pore Volume equation? It is confusing.
DeleteAnon, do you mean it's not corrected on the Kindle? If so, when did you last download yours? Because Amazon doesn't update old versions I think.
DeleteOn problem 2018 #3: I would also think B) offset angle of 0.0375" for hard formation is false. I believe offset angles for hard formations needs to be 0deg according to SPE PE-Petroleum_Engineering_Handbook-2-Drilling_Engineering-Mitchell-2006 pg224. How do you decide which is more false?
ReplyDelete