Re: Influence of Igneous Emplacement on Petroleum Systems
"In Altiplanicie del Payu´ n area, both the Upper Jurassic Vaca Muerta and the Cretaceous Agrio source rocks are largely immature (0.4–0.6% VRE). However, significant thicknesses of source rock have been locally matured by thermal anomalies related to Tertiary intrusions of alkaline laccoliths. Commercial oil accumulations (20– 33API) and oil shows have been identified along the entire stratigraphic column, both in sandstone/carbonate and fractured overpressured igneous reservoirs."
"The good geochemical correlation between oils and source rock samples from the study area, having a different molecular signature than burial generated oils from deeper areas of the basin, is interpreted as the result of local maturation processes during emplacement and cooling of the igneous rocks."
Fascinating that they've identified commercial accumulations from local maturation such as this. I'm just wondering how viable this can be as the sole source of hydrocarbon generation.
Had a search around for the diamondoid technique.
"diamondoids, a class of petroleum compounds whose unique thermal stability leads to their progressive concentration during cracking, can be used to identify the occurrence and estimate the extent of oil destruction and the oil deadline in a particular basin. We are also able to identify oils consisting of mixtures of high- and low-maturity components, demonstrating that our method yields valuable information on the cracking and mixing processes affecting petroleum systems."
I suppose the insight into the mixing process helps them assume that local heating did occur. I'm wondering however whether the interaction between these high maturity and low maturity sources may just be down to a very high thermal gradient and extensively thick source rock.