A well’s surface section is drilled to 8,000 ft TVD where the pore pressure is 3,000 psig and the fracture pressure is 6,000 psig. At 4,000 TVD the pore/fracture pressures are 1,500/4,000 psig, and 5,000/8,000 psig at 10,000 ft TVD.
Assuming a trip margin of 200 psi and a kick margin of 500 psi, and a future intention to drill to 10,000 ft TVD once the surface casing is set, the maximum mud weight allowed to drill the surface section is closest to:
(A) 14.1 lb/gal
(B) 13.2 lb/gal
(C) 13.5 lb/gal
(D) 13.8 lb/gal
This is pretty simple once you've read through all the details. See 6 DTC 6 (csg set depth) and it has the single needed equation: Max MW=(Pff - KM)/0.052(TVDshoe) = (5,000-500)/(0.052*8,000) = 13.2 or (B). The GB has the exact problem as an example.
Monday, July 20, 2020
Wednesday, July 15, 2020
Casing Design: 2017 #54
A well’s production casing will be set at a TD of 16,000 ft in 10.2 lb/gal mud. Which statement is most FALSE?
(A) Production casing design should start at 16,000 ft and move uphole.
(B) Casing collapse resistance must be reduced for tension if below 13,500 ft.
(C) Casing collapse resistance needn’t be reduced for tension if below 14,500 ft.
(D) Casing collapse resistance must be reduced for tension for casing above 12,500 ft.
This problem has a lot of garbage you don't need (I don't include it here). (A) is clearly true (csg design starts on bottom and moves uphole; look up as needed). (B) through (D), however, are really the same question regarding collapse in relation to depth.
Solution: See Guidebook 6 DTC 9 that covers casing design and the neutral plane. Next, look up the 10.2 ppg buoyancy factor to calculate the hole section's neutral plane (16M*0.844 = 13,500 ft). The rest is academic; as TS 12 puts it on P430: Collapse performance properties will require derating for tension above the neutral plane. So (B) is false.
But watch the wording on these types of problems like a hawk. You might work 5 minutes then mess up the answer due to some double-negative in the wording, confusion over "above" versus "below" the NP, or if the text is actually "true" or "false", even if you understand the problem fully. For this reason I always save 30 seconds for a check/re-read of each problem. Paranoia here is your friend.
(A) Production casing design should start at 16,000 ft and move uphole.
(B) Casing collapse resistance must be reduced for tension if below 13,500 ft.
(C) Casing collapse resistance needn’t be reduced for tension if below 14,500 ft.
(D) Casing collapse resistance must be reduced for tension for casing above 12,500 ft.
This problem has a lot of garbage you don't need (I don't include it here). (A) is clearly true (csg design starts on bottom and moves uphole; look up as needed). (B) through (D), however, are really the same question regarding collapse in relation to depth.
Solution: See Guidebook 6 DTC 9 that covers casing design and the neutral plane. Next, look up the 10.2 ppg buoyancy factor to calculate the hole section's neutral plane (16M*0.844 = 13,500 ft). The rest is academic; as TS 12 puts it on P430: Collapse performance properties will require derating for tension above the neutral plane. So (B) is false.
But watch the wording on these types of problems like a hawk. You might work 5 minutes then mess up the answer due to some double-negative in the wording, confusion over "above" versus "below" the NP, or if the text is actually "true" or "false", even if you understand the problem fully. For this reason I always save 30 seconds for a check/re-read of each problem. Paranoia here is your friend.
Saturday, July 11, 2020
Separator: 1017 #53
Problem 53. What is most FALSE about oilfield separators:
(A) Horizontal handles foam but not solids more efficiently than vertical...
(B) SPEC 12J is the standard API reference for oil & gas separator design.
(C) Gravity separation section: reduces entrained liquid load & improves gas velocity profile.
(D) Souders-Brown approach for sizing the gravity separation section...is no longer recommended.
This is a general separator question; see 8 FAC 5. This page quickly shows that A & B are true. Say 90 seconds down.
General knowledge tells me C is true as well, leaving D as the answer; I mark that at 2 minutes.
However, I prefer verification. I'm checking references; the Guidebook recommends HS3 P15-47 and 12J, so I go to HS3 first. After another two minutes I verify from the text that C is indeed true.
Now I'm on to D. I'm pretty sure it's the answer, but again I want to verify this and so check the HS Index for Soulder. Nothing. I check the Dictionary? Nothing. Bradley? Nothing! Next 12J, which I happen by luck to have (1999 edition)? Nothing! Out of desperation, I check Mian. Nothing!! I'm now past my 6 minutes, But I'm pretty sure it's D from process of elimination and I move on. I've wasted a lot of time I could have invested elsewhere.
But for those curious, basically 12J uses a Ks factor via the Souders-Brown equation as an empirical parameter (but never really tells us the how or why). As we have seen, it's is not obvious in any of the common references. Be prepared for this; the solution may not be in any book you have and you must use your experience, common sense, test-taking skills, and the process of elimination. Watch the clock like crazy when using references. As I often say: a person's chances of passing an open-book exam is inversely proportional to the number of pages referenced. And most of the time, it's just a waste of time.
(A) Horizontal handles foam but not solids more efficiently than vertical...
(B) SPEC 12J is the standard API reference for oil & gas separator design.
(C) Gravity separation section: reduces entrained liquid load & improves gas velocity profile.
(D) Souders-Brown approach for sizing the gravity separation section...is no longer recommended.
This is a general separator question; see 8 FAC 5. This page quickly shows that A & B are true. Say 90 seconds down.
General knowledge tells me C is true as well, leaving D as the answer; I mark that at 2 minutes.
However, I prefer verification. I'm checking references; the Guidebook recommends HS3 P15-47 and 12J, so I go to HS3 first. After another two minutes I verify from the text that C is indeed true.
Now I'm on to D. I'm pretty sure it's the answer, but again I want to verify this and so check the HS Index for Soulder. Nothing. I check the Dictionary? Nothing. Bradley? Nothing! Next 12J, which I happen by luck to have (1999 edition)? Nothing! Out of desperation, I check Mian. Nothing!! I'm now past my 6 minutes, But I'm pretty sure it's D from process of elimination and I move on. I've wasted a lot of time I could have invested elsewhere.
But for those curious, basically 12J uses a Ks factor via the Souders-Brown equation as an empirical parameter (but never really tells us the how or why). As we have seen, it's is not obvious in any of the common references. Be prepared for this; the solution may not be in any book you have and you must use your experience, common sense, test-taking skills, and the process of elimination. Watch the clock like crazy when using references. As I often say: a person's chances of passing an open-book exam is inversely proportional to the number of pages referenced. And most of the time, it's just a waste of time.
Monday, July 6, 2020
Fishing: 2017 #48
Problem 48. This is a standard problem just like in the Guidebook on 6 DTC 10. Math below. Note how much quicker using the "sc" chart for the tubing and casing is than doing the entire FL/EA calculation each time:
10,000 lbf(8103’ dp)1.5444E-07 (sc for dp) = 12.5”.
20.5” – 12.5” = 8”.
8”/[(10,000 lbf)1.1047E-07] (sc for tbg) = 7,243’ (A).
10,000 lbf(8103’ dp)1.5444E-07 (sc for dp) = 12.5”.
20.5” – 12.5” = 8”.
8”/[(10,000 lbf)1.1047E-07] (sc for tbg) = 7,243’ (A).
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