BIG HORN COUNTY, MONTANA - Clearmont, Wyo.–based Alta Vista Oil (Alta Vista), who appears to be representing Apache Oil, has a new field discovery at a remote site located in the northwestern portion of the Powder River Basin in Montana. Spotting some 2 miles north of the Wyoming border and almost 17 miles northeast of Sheridan, Wyo., production data submitted to the state of Montana reveal the Slaughterville #1H, nw-ne 28-9s-41e, Big Horn County is a horizontal Mowry discovery. Whether or not it is commercial is yet to be determined, however according to the state, during 19 days in August, the Slaughterville #1H produced 2.57 k bo, 9.46 mmcfg and 25 k bw from the Lower Cretaceous Mowry. Although still being held confidential, this exploration wildcat was originally set up to evaluate the Mowry at a true vertical depth of 8,867’, with a measured depth of 12,188’. The lateral leg is expected to land in the sw-se 28-9s-41e. Although there are numerous horizontal Mowry producers found on the Wyoming portion of the Powder River Basin, the Slaughterville #1H represents the first Horizontal Mowry producer within the state of Montana as well as the first horizontal test drilled in the Montana portion of the Powder River Basin.
In what maybe a good indication as to how Alta Vista views their new field discovery, the company has announced plans to drill a north offset to the Slaughterville #1H, at the Doc Holiday #1H se-sw 21-9s-41w, a horizontal Mowry test that will have a bottom hole location terminating in the ne-nw 21-9s-41e. Presumably attempting to move up-dip, estimated true measured depth for this effort will be 12,465’. No activity has been observed at this location.
The only recent drilling near Alta Vista’s discovery has been for shallow coal-bed methane reserves on both sides of the Montana state line. There are, however, three conventional wells within a 3-mile radius of the Slaughterville #1H site. Two miles northwest of the discovery well, Shell Oil sought oil deposits primarily in the Muddy at the Government #31-19, nw-ne 19-9s-41e. This vertical test bottomed in the Jurassic Morrison at a total depth of 8,850’. Although no drillstem tests were performed in the well bore, Shell did cut a core in the Lower Muddy between 8,275’ and 8,334’. According to the well’s postmortem report, some residual fluorescence was noted across this interval.
Plugs from the core evaluated with mercury injection tests indicated poor porosity and permeability. Shell did not record any significant Mowry shows. No production casing was run, and the operator plugged and abandoned the Government #31-19 in 1969. Log tops of this failure include the Mowry at 7,893’, Muddy at 8,182’, Lower Muddy at 8,250’, Dakota at 8,413’, Lakota at 8,664’, and the Morrison came in at 8,746’.
Nearly a century ago, Absaroca Oil Development (Absaroca) drilled a wildcat a mile northeast of Shell’s Government #31-19 and roughly 1.5 miles northwest of Alta Vista’s new producer. One of the earliest oil hunters in the state, Absaroca used cable tools to punch in the AOD Well #1, se-se 17-9s-41e. After achieving a total depth of 3,485’ in the Upper Cretaceous Pierre Shale, this attempt was abandoned in 1918 with no known significant shows encountered.
Three miles southeast of the Slaughterville #1H and across the Wyoming border, Wexpro Company drilled a straight-hole Pennsylvanian test at the Fordyce #14-29, ne-ne 29-58n-81w, which accessed the Minnelusa at a depth of 10,803’. No cores were taken or tests were noted, and Wexpro put the cement to this failure in 1972.
The closest established oil production to the Alta Vista venture is approximately 18 miles to the southwest at Ash Creek South Field, a large anticlinal nose that plunges basinward from the Big Horn Uplift. Discovered in 1954, this reservoir, which is one of the few conventional Cretaceous resources found in the northern Powder River Basin, has cumulated more than 9.6 mmbo primarily from the Ash Creek member of the Shannon at depths approaching 4,720’.
The nearest lateral production to the Slaughterville #1H is some 25 miles to the southwest at the Educated Guess #11-1H, ne-ne 10-54n-83w, Sheridan County, Wyoming. Drilled by Austin, Texas–based Onshore Holdings, this horizontal Mowry discovery was completed for an IPP of 102 bopd, 34 mcfgpd, and 951 bwpd from the open-hole lateral interval at 12,220’–16,920’. Bottom hole for the Educated Guess #11-1H terminated in the se-ne 11-54n-83w. Completed in 2013, this well, which has been shut-in since April 2015, has accumulated more than 4 k bo, 845 mcfg, and 11 k bw.
The closest conventional activity to the Educated Guess #11-1H is almost a mile to the northeast at a vertical failure drilled by Macum Energy. The State #42-2, se-ne 2-54n-83w, achieved a total depth of 8,424’ in the Upper Cretaceous Shannon. No cores were taken or tests were performed, and this dry hole was abandoned in 1994.
It is interesting to note that operatorship of the Educated Guess #11-1H strike was assigned to Denver-based Cirque Resources a company that has been involved in various horizontal plays throughout the Rockies. It may be recalled that in the latter part of 2011, Cirque announced plans to drill a horizontal Mowry wildcat at the Marilyn Merlot #26-16H, se-se 26-56n-83w, Sheridan County, Montana.
Scaling some 15 miles southwest of Alta Vista’s Slaughterville #1H, the Marilyn Merlot #26-16H was scheduled as a 15,142’ (TMD) Mowry attempt with a bottom hole terminating in the nw-nw 26-56n-83w. Cirque indicated that based on 640-acre spacing, the ultimate oil recovery for the Marilyn Merlot #26-16H would be approximately 414.1 k bo. This well was never drilled, however, and the permit was allowed to expire.
As mentioned, Apache Oil appears to be bank rolling Alta Vista’s program in Big Horn County. The last time this company showed up in Montana was in 2013 where the company drilled three Bakken/Three Forks wildcats on the western flank of the Williston Basin in Daniels County. Locating in the overall area of 36n, 47e–48e, all three of these attempts were abandoned with no significant shows reported.
Story and graphic courtesy Rocky Mountain Oil Journal, www.rmoj.com