The Alberta Bakken/Exshaw Resource Play of Northwest Montana: Where Did All the Oil Go?

Abstract

Northwest Montana experienced a flurry of exploratory drilling activity between 2010–2013, in an attempt to establish a "Bakken-type" oil resource play in Northwest Montana. Companies were lured to the so-called “Alberta Bakken” oil resource play by the prospect of shallower drilling than North Dakota, and the availability of large lease blocks. Some 40 tests drilled by four companies were scattered over 5000+ square miles in an area of northwest Montana which had few previous deep wells. Many of these tests produced some oil from the Middle Bakken, but all of them have since been plugged or shut-in. In some cases, duplicating the horizontal completion practices perfected in the North Dakota Bakken, have been ineffectual in northwest Montana due to marked changes in the stratigraphy. One company successfully established the first horizontal oil production west of the Sweetgrass Arch from the Devonian Nisku Formation, but the well is currently shut-in. A recent study by Wood McKenzie estimated that the Bakken/Exshaw petroleum system of Montana/Alberta has generated 2.6 billion barrels of oil. If the majority of Bakken-generated oil is no longer in-place, where did it go? Good oil shows from the few scattered deep tests on the Blackfeet Indian Reservation, indicate there may be a bypassed pay zone in the Mississippian which occurs in the lower Lodgepole Formation. Some of the Bakken-generated oil may have migrated upward into this tight, fractured, carbonate reservoir. Additional oil may have migrated downward into the Devonian Nisku Formation. Future exploration efforts in northwest Montana should focus on the search for traps containing "migrated" Bakken oil, rather than attempting further completions in the Bakken Formation itself. A Bakken-sourced oil resource play may still be feasible if the right trapping conditions can be found.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015