A model was developed for oil generation in the Devonian and Mississippian Bakken Formation, which has been proposed as the main hydrocarbon source rock within the Williston basin. The data consisted of formation temperatures and of density, neutron-porosity, resistivity, and gamma-ray logs from more than 250 wells in North Dakota and Montana. The upper and the lower shale members of the Bakken Formation were studied. Regression analysis, analysis of residuals, and cluster, discriminant, and factor analyses were used in an attempt to separate depositional effects--especially variations in organic content--from maturity.

Regression and analysis of residuals indicate differences both areally and between the upper and lower members. In the upper member, and less strongly in the lower member, the center of the basin differs from the basin margins in that it has extreme residuals--either high or low. Clustering and residual analyses show roughly the same areal patterns.

Inverse relationships, similar to those suggested by other workers, were found between formation temperature and organic content and between density logs and organic content. Also found, though, was that the addition of other factors, such as neutron porosity, helps to indicate organic content.

Preliminary results show that it may be possible to model oil generation by using statistical techniques on well-log data. In particular, the model has the potential to refine estimates of the amount of hydrocarbons generated by the Bakken Formation in the Williston basin.

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