Thermogenic Hydrocarbons In Lake Sediments Over Oil and Gas Fields (Mackenzie Delta, NWT, Canada) Organic-rich lake sediments were collected at 1 to 2 km intervals over Tertiary and Devonian oil fields and the 2000-m deep Cretaceous Tuk gas field during an orientation geochemical survey in 1991. The objective of the survey was to determine if thermogenic hydrocarbons in the headspace of lake sediments could provide an indication of underlying oil and gas fields. The total cost of the survey was $19,000 or $130 per km2. Headspace gas from the lake sediments was analyzed for C1-C6 hydrocarbons. Thermogenic hydrocarbon anomalies are evident over and around the oil and gas fields as indicated in Figure 1 and Figure 2 on the back page. The presence of thermogenic hydrocarbons in lake sediments suggests that this geochemical method could be effective for regional exploration of the Mackenzie Delta. The method would help focus more detailed exploration with geophysical tools.

Figure 1. Distribution of headspace pentane in lake sediments over the Tuk and Mayogiak oil fields and the Tuk gas field (Mackenzie Delta, NWT, Canada).

Figure 2. Distribution of C2-C6 factor scores in lake sediments over the Tuk and Mayogiak oil fields and the Tuk gas field (Mackenzie Delta, NWT, Canada).

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