Diagenesis and provenance of the Middle Jurassic sandstones and carbonates of the Mohican Formation in Mic Mac H-86, Mohican I-100, and Wyandot E-53 wells, offshore Scotian Basin

Abstract

Diagenetic processes can be studied to determine the oil and gas reservoir potential within a sedimentary basin. The majority of focus within the Scotian Basin has been on Lower Cretaceous sandstones, with minimal studies done on the Middle Jurassic sandstones that appear in the Mohican Formation of the Scotian Basin. To increase potential oil and gas exploration in the future, it is important that other areas of the Scotian Basin be studied, such as the Middle Jurassic sandstones. To understand the diagenetic processes that occur in the Mohican Formation wells, petrographic data, lithofacies descriptions, X-Ray diffraction data, chemical mineralogy, and porosity and permeability data were combined and analyzed to determine reservoir potential in this part of the Scotian Basin. To determine provenance of these sandstones, petrographic data was used to observe minerals and textures of lithicclasts and compared to samples from known potential sources from elsewhere in the onshore area. Petrographic data shows that diagenesis in the Middle Jurassic Mohican Formation is similar to that of the Lower Cretaceous sandstones previously studied. However, main differences occur in the chemical mineralogy of minerals, particularly chlorite. Chlorite within studied wells contains high MgO wt% and low FeOtwt%, whereas in the Lower Cretaceous sandstones there is low MgO wt% and high FeOtwt%. This suggests that chlorite diagenesis is variable throughout the basin. Provenance studies show that most detrital minerals, within the studied samples, likely come from the Meguma Supergroup slates and meta-sandstones, and the Meguma Terrane granites, which also provide detrital minerals throughout other parts of the Scotian Basin, either as first or second cycle detritus.