Well performance prediction using DT-1's
This discussion/question is sort of related to the "Production flow data from early HS wells" discussion, which was more about production and production decline than pressure issues, but pressure issues were mentioned. So I have been trying to make the most out of available data, and it looks like the two best sources for telling what a well is currently doing, and will do are 1) the actual production data, until such point that there is more than 1 well in a unit, and 2) the DT-1 tests. I have sort of deciphered the DT-1 tests, assuming that "GAS DEL" is basically MCF/D production under test conditions, for the given CHOKE (which I would guess is the current production choke), that WATER is barrels of water a day, which I am presuming is most desirably around 0, but not uncommonly around 100, and finally FLOWING PRESSURE. Being naive, I would think that FP x CHOKE**2 would be proportional to daily production; this does not seem to be the case, but it does correlate somewhat. SO if the FP is really low, I am presuming that is bad, and at some point they start compressing the well (which costs money), and when it gets truly abysmal, the well maintnenance guys go hunting around for some sacks of concrete and P&A the poor sucker. So I have a well, reasonable first check given the IP was about 8MMCF/d (produced 160MMCF for first check); there clearly are some challenges over in the T12N-R9W and T12N-R8W area; with wells varying in IP between 3 MMCF/d and 25 MMCF/d (so in these two townships, there have been 12 completed wells; 4 between 3-10 MMCF/d IP, 3 between 10-20 MMCF/d IP, and 3 between 20-30 MMCF/d IP (more data available no doubt; this is just what is on sonris). I need to check back and see if some of these might have actually tapped the BS instead of the HS - that could make sense, but otherwise, it looks highly variable in this region, but trending down rather fast W to E (I am right on the W to E township line. So I got sidetracked, but this is something else to comment on / think about - variability between near wells - is the shale that variable, or is it simply random events in drilling, or what? But back to the main question - FP is I am presuming pretty useful, though actual gas delivered in a DT-1 is probably the MOST useful number ;-) But what does low FP really tell you? This "well of interest" was delivering over 4 MMCF/d (not great I know, but better than some...) on a DT-1 after a bit more than a month; the FP had already dropped to 1500. I can speculate on several things that would cause FP to drop (less gas, fines plugging the fracture cracks, water still slowing things down maybe); but does this prognosticate anything in particular? Seems that the actual gas production is above typical gas production for this sort of FP. Also, when do they move to compression to keep gas flowing? I noticed a compression fee on my first check - largest deduction that was made; I am presuming this is even further up-pipe, at the point where flow from many wells is going into a pipe, but of course don't really know. So apologies in advance for the all-over-the-place question, but I would appreciate clarification of any misconceptions and addition of any insights about reading this sonris data as it is starting to actually accumulate. Ultimately, I know that what arrives in the mailbox is the best indicator, but I am sure that I am not the only mineral owner out there plowing around in sonris, trying to predict what is in store for us, especially closer to the edges.
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Replies to This Discussion
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Permalink Reply by Robert Duke on
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Hmmm, Okay, can I get you to elaborate a bit further on this? Are you saying that sonris data is inaccurate, incomplete, or both? I am guessing the viewpoint here is that the O&G company has much more data from which they can figure out what is going on, and reading sonris is really only marginally better than Tarot cards for this purpose. That combined with the fact that the prognosticators at the O&G companies actually know what the heck they are doing in looking at all the numbers. and probably biggest problem of all, knowing what is really going on is competitive data - stuff one O&G does not want a non-JV O&G to know. I just wish that as mineral owners, we could make slightly better predictions ourselves, but honestly I have moved on in terms of being able to do any financial planning based on looking at what is happening in the play - just too much uncertainty at many, many levels. I also wish the O&G would share more data with the mineral owners, but realize they have that competitive stuff going on, and spend most of their data-distribution efforts on investors (really the only reason I can think of to help out the mineral owners is to enhance their reputation as great folks to lease with).
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Permalink Reply by FXEF on
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Robert,
IMHO, SONRIS data is accurate, but not always current. I'm not sure that a reservoir engineer with much more data than SONRIS provides can make performance predictions that would be useful to royalty owners. The operator is working to get maximum production.... they stand to lose more than we do.
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Permalink Reply by Robert Duke on
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Hi folks,
One other factor I looked at - well depth. Most of the good wells in this area have a "true vertical depth" listed in the 13000-13400 ft range. The really bad wells have TVD listed around 13800 ft (really consistent depth listings on the bad wells, they are separated by at least 3 mi N-S, which is the total N-S spread for all but one of the wells in my sample). My sort-of-who-knows, 8 MMCF/d IP well has a TVD listed of 12200 ft! (in the middle of the N-S spread). Sort of different, but I am presuming all HS? (seems I remember BS around 11000 ft). Are these numbers real? I believe the shale trends deeper to the south, but we are basically talking about less than 4 mi movement. I know I am probably busy trying to overanalyze, but just looking for some real knowledge, and I am an inveterate "if there is data, I will attempt to make sense out of it guy (apologies to anyone who has pulled their hair out :-))".
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Permalink Reply by Robert Duke on
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Oops, just noticed in my well performance breakdown for the 2 townships, I screwed up in that there are actually 5 wells producing 20-30 MMCF/d, not 3. So about half the time the wells have been fantastic, and all the fantastic wells were drilled between 12945 ft and 13585 ft., scattered around top half of 12N-9W (but top half is where bulk of wells are in both townships - all but 1)
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Permalink Reply by Les Bamburg on -
Robert, you may want to focus on one topic at a time - that will help in getting you answers and guidance.
By the way, make sure you are looking at TVD's as drilled rather than the original permit. Yes, the Haynesville Shale Shale generally trends deeper to the south and southwest. In some areas the dip can be very steep.
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Permalink Reply by Robert Duke on
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Hi Les,
Yes, sorry about making it more complicated than necessary, and I suspect I ask lots of questions that are sort of difficult to answer, even speculatively; my mind is wandering all over the problem space, I start collecting/analyzing data, and whoomp! - word explosion. Let me break this down into two key questions; I can extract the essence of the 2nd question into a second thread if it goes unanswered here, but it may be more efficient to let folks that are willing respond to 1) and/or 2) here first, and then only re-ask if necessary:
1) Can you or someone else comment on the significance of flowing pressure measurements? I have a rudimentary understanding, but looking for a little field based experience.
2) I started surveying all the well TVD's in these two townships (the numbers with the final date on them in the "bottom hole coordinates" section of a sonris well listing - really the majority of the wells are in roughly the NW half). The TVD's only make sense to me in these two townships if the driller is hunting around a bit. I am presuming they are all HS, but I am struck by the fact that there are two wells about 1.5 mi either side of 240843 that were drilled to TVD of about 13,900 ft (both low yield wells), and right between them is 240843 drilled to 12200 ft. Then all the fantastic wells are at an intermediate TVD - we are talking 5 wells mostly within 2-4 miles I think, > 20MMCF/d IP. So I am not seeing a depth trend here. I presume they make their best guess on when to turn horizontal based on a rough depth estimate and coring samples? I guess I am hoping wells in this area may do better when drilled to the "success" depth, but I am of course information-challenged.
Thanks for being patient; I'll attempt to not ask for a Petroleum Engineering textbook in every question...
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Permalink Reply by Les Bamburg on
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Robert, I will try to tackle item #2 first. I have attached a grid with my estimate of the Haynesville Shale formation depth near the well surface location. The depth shown on Sonris is the TVD at the bottomhole location and has not been adjusted for elevation. The depth for Ser #240843 has not been updated and should have a TVD at the BHL of ~ 13861'. You will see there is a definite trend deeper in depth to the south and southeast.
In some areas the formation dip is fairly steep and can vary along the lateral path. Also recognize operators are trying to target a certain layer within the HS and this can be challenging in this area because there is little or no data from previous vertical well penetrations. - Attachments:
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HS Depth T12N-R9-8W.pdf, 47 KB
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Permalink Reply by w.r. frank on
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Les,
A great grid would be to do a T & R grid (no sections) from 17N to 9N and 9W to 16W that did HS and BOS with color codes for HS and BOS. In Sabine, there are a lot more BOS wells than people realize. The only way to tell is the TVD.
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Permalink Reply by Robert Duke on
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See the PHK "HS Structure" map I attached to my reply below - it is a start (gives HS depth contours), but it does not tell you where the BS is. I vaguely remember something somewhere that led me to believe the BS trends somwhere between 1000 and 2000 ft shallower, but I am just a small mineral owner, pouring over a bunch of data...
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Permalink Reply by Robert Duke on
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Hi Les,
Thanks much for taking a shot at this. So in an attempt to not bombard you with all the depth data I have extracted from sonris on 4 wells trending from NE to SW in this area, all not fantastic producers (240963 S5-12-8, 240843 S7-12-8, 241178 S24-12-9, 240709 S14-12-9), are you basically saying that you have additional info outside sonris that allows you to come up with a TVD for 240843 of 13861 ft? Or am I missing something in sonris? I could construct tables of the sonris data, and other than the fact that the 240843 TVD is anomalous, I don't see it (okay, I do see that measured depth, perf upper/lower locations, ground elevation are all certainly closer than TVD, and it just makes sense that the entry is incomplete, so I would buy that - you know what to expect from the broader data). If I look at p40 of the PHK 05/24/10 presentation (attached single page), there is a "Haynesville Structure" contour map showing depths trending from about 14000 to 14500 ft, running roughly from NE to SW (more like NNE to SSW). The rate of depth increase is about 1000 ft per 4-5 miles across the contours in this area; great wells just upstream (3-4 mi say) on this sinking slab of shale but of course I know nothing about how quickly thickness, porosity, gas content, temperature etc. is changing; I also don't know how good the PHK data is (I am presuming it is seismic rather than sampling, but I know nothing about methods on this stuff). My likely conclusions: 1) all these wells are roughly to same depth, despite TVD in sonris, trying to hit an equal depth slice of HS, 2) for some reason it is not that productive over here on this contour, 3) I don't really know if they hit the contour that well, or if they can do anything to drill better HS wells in this area, 4) I don't know where the BS is in this area, other than shallower, but would guess it is a better prospect. - Attachments:
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PH_052410 9.pdf, 206 KB
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Permalink Reply by FXEF on
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Robert,
You will sometimes need to search WELL ENGINEERING/MECHANICAL in SONRIS and read the measured survey logs to get that data.
240963 S5-12-8, 13621 TVD / 17727 MD
240843 S7-12-8, 13861 TVD / 17638 MD
241178 S24-12-9, 13893 TVD / 17613 MD
240709 S14-12-9, 13891 TVD / 17950 MD
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Permalink Reply by Robert Duke on
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Oh wow, thanks FXEF! Okay, so there is basically more data in sonris than "sonris lite"; it is not purely a matter of a more complex but more functional interface; there is actually more data. So I need to go figure out how to use real sonris, looks like :-) Thanks much for that insight, as well as the datum above, showing consistency in TVD for the wells on this NE - SW trend!
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