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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 93-102

Organic Geochemistry of the Lower Cretaceous Ostracode Zone, a Brackish/Non-Marine Source for Some Lower Mannville Oils in Southeastern Alberta

C. L. Riediger, M. G. Fowler, L. R. Snowdon

Abstract

The Lower Cretaceous Ostracode Zone has hydrocarbon source rock potential in southern Alberta. This unit is variable in both lithology and organic geochemical characteristics, reflecting fluctuating depositional conditions. Organic matter characteristics are consistent with deposition of the Ostracode beds in a restricted, brackish to freshwater environment, such as an estuary or embayment. Oil-prone Type I and II kerogen is typical of most Ostracode Zone samples examined in this study, with a few intervals containing gas-prone Type III kerogen. Total organic carbon (TOC) contents range up to 7% for Type I to II kerogens, whereas TOC values as high as 11.7% are recorded in samples dominated by Type III kerogen.

The Ostracode Zone is thermally mature over a broad region, and hence some quantity of oil must have been generated in and expelled from this unit. This is confirmed by biomarker analysis, which demonstrates a correlation between Ostracode Zone rock extracts and several oils from the Provost field in eastern Alberta. A suite of unusual and unidentified compounds, designated the “Q” compounds here, occur in both the extracts and the oils. These compounds may be used as marker compounds for Ostracode oils in western Canada, as they have not been detected in other source rocks from this basin.


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