A 160-173-54 PU. 16 SPM. 200 BFPD. Rods have no significant
stretch. 1.5 inch diameter pump. Anchored. Fluid SG 0.9 at 4,500 ft. Lift system
volumetric efficiency?
The PD equation is on 7 PRD 9 (note we can use S for Sp since there is assumed no rod stretch):
Pump Displacement (ideal) = 0.1166(54 in)(16 spm)(1.5^2 in^2) = 227 BFPD
Pump Displacement (actual) = 200 BFPD
200/227 = 88% (B)
The provided Reference Guide can only hurt you on this problem; any time spent looking in chapter 4 (rod pumps, pg 124-131) is only wasted time. IMO, this is a big weakness for this reference; what good is a PE reference without the rod pump displacement equation? UPDATE: the SPE Reference Guide does have 9702.03 ci/bbl under Constants. and a % Clearance Volume for a Single-acting Cylinder equation (page 151 under Facilities) that can be manipulated so as to be close to the PD equation. Note 9702.03/127 is 0.1169 not 0.1166, but 1% error is not going to matter.
Regardless: know all terms and how the pump designation works (HS V4 pg 489) plus the 0.1166 volumetric conversion constant (HS V4 pg 471). Note you cannot use a direct volume conversion (cubic inches/bbl & min/day) as the number will be too large. 0.1166 is an easy number to memorize though, and the rest is just pump volume.
David,
ReplyDeleteThe SPE 2014 practice exam includes a rod problem with an 86 rod number, 5,000 ft installation depth, and 2.0" plunger diameter. The question asks for total length of 1.0" rods. I used page 128 in the RG, which shows 32.8% 1.0" rods in this case = 1,640 ft of 1.0" rods. Is there a trick to these problems? The answer key says the answer is 1,435 ft.
I haven't looked at the 2014 recently so I can't speak to it. I've heard it has some errors though.
DeleteThanks for your response. Also just a note for the problem above - RG page 125 has q=0.1484(ApNSpEv), which seems to work. And RG page 130 has a table with pump factor 0.1166xD^2, which is a good reminder if needed during the test.
DeleteThanks! Rod pumps are not my strength (not used in my area) so I'm always looking for suggestions.
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