You must be not very far from where I have worked the last 6 years.
We are trying re-entries on some older leases that date back to the mis- ‘80’s. The casing sizes were the biggest problem, due to the extreme glut of casing then, they used 39# 7” and that posed a tool annular of only 5 7/8”. The difficulty to find motors, bits and tools that would work well in a 5 1/2” hole was beyond logical. those 4 3/4” tool joints pretty much put a serious bind on our build rate. WE came out 15 feet below the DIP line when we landed the curve. We wound up in the Three Forks and couldn’t get out of it. So, we rode it all the way to T.D. The ROP was in the 6 to 8 foot range. (PDC included)
The well was fracked just last week and it came in hot and nasty! It kicked hard and we had to feed it 14.8# kill wt. invert with a yield point of 16 or higher. We fugure the initial flow will average 2500 to 3000 BBl Per day for the first 90 days and then level off to near 8 to 9 hundred.
I doubt we will do any new re-entries, but our next several wells will follow that plan that we stumbled on to. We have targeted all of them in the Three Forks.
Any comments?
So you are the guys I've heard a rumor or two about.
Thoughts: over in the New Town area (Sannish is the town) there is a sand at the base of the Bakken/top of the Three Forks. The contact is an unconformity, anyway, so it stands to reason the eroded material went somewhere--and that it would be tough to identify in drilled samples, especially with a PDC where you get milled bits of what is there anyway, and individual grains might be tough to pick out as a separate unit or layer.
I would not be surprised if there were similar development elsewhere in the basin.
I'd bet you fracked into such a stringer, and it might show up on the old resistivity logs at the contact/Three Forks top as an invaded zone. If so, it could be picked out as a target. (It sure would have drilled better than 6 to 8/hr if you were in it, more like 60-80, at least with the 6 inch hole we have been cutting (bigger tools, and all that).
Maybe on the CNL/LDT as well, but there might be a small crossover (just a couple of percent like you get with chert in lime) if it is on a limestone matrix, because of the density difference between limestone and sandstone.
Any gas on the old mudlogs would be tough to pick out because of the normal gas peak seen coming out of the lower shale.
Drilling wise, it would be hard to get up out of because it may be loose (or poorly cemented) grains. We had the same problem in some granular limestone over on the Nesson Anticline, and had to slide for some 30+ ft before we could get enough ledge built in the roof to climb out of it. Rotate, and all those grains break up, you trough the formation, and you are right back where you were with no gain. It idn't show up as a sandy layer on the Gamma Ray, but it sure behaved like one.
Fun stuff isn't it?
Sheesh! we usually run 29# 7-inch, (32# in the salts). Thirty nine? Wow. Talk about overkill.