Abstract

In the Jenner-Suffield area (T18–21, R7–9W4) the Lower Cretaceous upper Mannville Group produces heavy oil (959 kg/m³-16° API) from a number of pools including the Jenner O, Jenner F and Suffield J pools.

These three pools have an initial estimated volume of oil in place of 48170 × 10³ m³ (312 mmbbl). Three informally named units are recognized within the upper Mannville Group in this area; UM1, UM2 and UM3 (oldest to youngest). Each of these units represent a fluvially backfilled valley incision event. The UM1 valley system trends NNW-SSE (1.5–3.0 Km in width), and rests disconformabiy on the underlying Ostracode Member. It is characterized by chert litharenites that typically fine upwards and have a coarse lag at the base of the sequence. The UM2 valley deposits are characterized by more feldspathic litharenites trending WSW-ENE. The UM2 valleys (0.5 Km in width) incise into the underlying Ostracode and the older UM1 valley deposits. UM2 sandstones are not of reservoir quality, probably due to alteration of feldspar to clays. UM3 sands are also chert litharenites. They trend NNW-SSE (1.0–1.5 Km in width) and amalgamate with the UM1 and Ostracode sands forming reservoir thicknesses up to 45m in the Suffield J Pool. The Jenner O and F pools produce predominantly from the UM1 deposit (minor Ostracode pay). The UM2 valley deposits form a partial updip seal on the Suffield J Pool separating it from the Jenner F Pool. All but the UM2 valley deposits have excellent reservoir potential.

Stratigraphic traps result where porous valley sands have laterally and vertically adjacent non-reservoir continental and coastal plain sediments, which are not genetically related.