With Recent Interest in Legacy Formations, Another Look at Those Formations

This was published in 2001, but is a nice review of the "Petroleum Systems" in North Dakota. I have not yet had a chance to read it completely. It is also linked at my "Welcome" page along with several other similar documents.

I thought this particularly interesting in light of folks claiming natural gas coming out of their faucets is due to fracking. Scientists have ways of "fingerprinting" oil and determining its source:

Chromatographic analysis of whole oil samples provides a “fingerprint” of hydrocarbons from C1 to C44, when present. An oil fingerprint is a histogram of the yield and distribution of resolvable compounds present in an oil. Quantitative results from these analyses were used to characterize and type these oils, infer source rock characteristics, determine thermal maturity, assess mixing or commingling of production, and predict oil expulsion temperatures. All oils were fingerprinted using whole oil, high resolution gas chromatography, while saturate and aromatic fraction biomarkers were assessed on selected samples from various key producing horizons. In addition, whenever sufficient sample was available, API gravities and sulfur contents were measured.

The article talks about source rocks and viability of various formations as pay zones.

The most interesting graphic: the slide depicting relative amount of oil produced from the various formations in North Dakota since 1951. One might as well have called the Williston Basin the "Madison Basin." But, of course, that is changing quickly with the Bakken.