ABSTRACT

A "synclinal truncation trap" is a combination trap (subtle trap) that occurs at the updip edge of angularly truncated reservoir rocks. The folded reservoir rocks may be truncated by erosion (angular unconformity), or by tectonic movements (thrust faults). Additional geological constraints are needed before hydrocarbon trapping can occur. These constraints are:

1. the truncation surface must be impermeable (seal) and tilted in the same direction as the plunge of the synclinal termination;
2. the reservoir rocks must lie on an impermeable stratigraphic unit and must be limited and preserved by an updip synclinal termination;
3. the reservoir's synclinal termination must be farther updip than the same reservoir's anticlinal terminations.

Synclinal truncation traps can be found worldwide in any petroleum sedimentary basin.

In Southeastern Saskatchewan, many oil fields related to the post-Mississippian angular unconformity are synclinal truncation traps. Ralph and Hume oil fields (Tp. 7 and 8, Rge. 12 and 13 W2M) are excellent examples of synclinal truncation traps. In Saskatchewan, Manitoba, and the Dakotas (Williston Basin), significant potential for oil pools of this same trap type may be found along the porous Mississippian subcrop belts as well as other Phanerozoic angular unconformities.

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