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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Petroleum Geology of the Cretaceous Mannville Group, Western Canada — Memoir 18, 1997
Pages 124-139

The Upper Mannville Group in Southeast Alberta, Canada: An Example of Multiple Incised Valley Fill Deposits

Rhea L. Karvonen, S. George Pemberton

Abstract

Valley fill sandstones within the Lower Cretaceous upper Mannville Group form the reservoir in a number of sizable heavy oil (959 kg/m3; 16° API) pools in the Jenner-Suffield area (Twps. 16-22, Rges.6-9W4). Estimated volume of oil in place is approximately 15.6 × 106 m3 (450 × 106 bbl). Three informally named units are recognised within the upper Mannville Group in this area; UM1, UM2 and UM3 (oldest to youngest). Each unit is characterized by a sandstone-rich lithology. These units are interpreted to represent fluvial backfilled deposits within an incised valley, distinguished from each other and older sediments mostly by stratigraphic correlation and mineralogy. Three UM1 valleys 1.5 to 3.0 kilometres wide are recognised, trending NNW-SSE, and incised into the underlying Ostracode or Ellerslie members. This unit is characterized by chert litharenite sandstones that are interpreted to grade from braided river deposits at the base upwards into sediments of a meandering system. The easternmost UM1 valley has been followed more than 160 kilometres, with the valley narrowing and deepening from south to north. The two UM2 valley deposits are characterized by more feldspathic litharenite sandstones trending WSW-ENE. The UM2 fluvial valleys average 0.5 kilometre in width and incise into the underlying Ostracode and the older UM1 valley deposits. UM2 sandstones are not of reservoir quality due to alteration of feldspar grains to clays. The single UM3 valley trends NNW-SSE, is 1.0 to 1.5 kilometres wide and consists of chert litharenite sandstones. The UM3 amalgamates with the sandstones of one UM1 valley and the underlying Ostracode Member, forming reservoirs up to 45 metes thick in the Suffield J Pool. The UM2 valley deposits form a partial up-dip seal on the Suffield J Pool, separating it from the Jenner F Pool. The Jenner O and F pools produce predominantly from the UM1 deposit (minor Ostracode pay). The UM1 also forms the reservoir in the Medicine Hat oil field to the south (Twp.23, Rge.5W4). Stratigraphic traps result where porous valley sands are laterally and vertically juxtaposed against genetically unrelated non-reservoir continental and coastal plain sediments.


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