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Several of the most important "disturbed belt" hydrocarbon occurrences are briefly summarized in order of discovery and development.
The hydrocarbon trap at Turner Valley is primarily structural; however, there are some indications of pre-structural stratigraphic control of accumulation. The Highwood structure, 2 miles west of Turner Valley, has tested only water from the Mississippian. Producing porous zones at Turner Valley can not be easily correlated with porous units at Highwood, indicating that there may never have been a direct connection between the two reservoirs. In addition, some wells drilled east of Turner Valley have encountered tight Turner Valley producing zones. Gas reserves originally in place at Turner Valley were 1.74 trillion cubic feet.
Hydrocarbons at Jumpingpound are structurally trapped in the updip edges of a thrust-faulted Rundle slice. Jumpingpound will eventually produce about 700 billion cubic feet of gas.
Surface geology in the Pincher Creek area does not suggest the presence of an anticlinal fold or large thrust sheet at depth. In contrast to steep west-dipping surface beds, the Mississippian rocks of the reservoir block at Pincher Creek dip southwest at only 4°-8°. Pincher Creek accumulation is structurally controlled. Current estimates give Pincher Creek 2.29 trillion cubic feet of gas reserves. During the past 5 years, four more important discoveries have been made in the Waterton and Castle River areas near Pincher Creek. Structurally these blocks lie above and west of the Pincher Creek block.
Total in place Mississippian gas reserves in Southern Alberta "disturbed belt" fields currently stand at 8 to 8.5 trillion cubic feet.
Early and recent oil and gas occurrences in the Montana part of the "disturbed belt" are briefly reviewed. Wildcat density, time of structural movement, degree of crustal shortening, and Mississippian stratigraphy are suggested as possible reasons for lack of economic success in the Montana part of the disturbed belt. Mississippian stratigraphy and its influence on hydrocarbon accumulations near the disturbed belt are illustrated with the suggestion that the combination of proper stratigraphic and structural conditions have not yet been found in the Montana disturbed belt.
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