USING XRD METHODS ON THE CYCLIC TYLER FORMATION (MORROWAN; LOWER PENNSYLVANIAN) IN WESTERN NORTH DAKOTA TO BETTER UNDERSTAND CLAY MINERALS AND THEIR EFFECT ON EOR AND SEQUENCE STRATIGRAPHY

Carbonaceous rocks within cycles of the Tyler Formation located in Western North Dakota are possible targets for enhanced oil recovery (EOR), but more work concerning the stratigraphic nature and mineralogical content of the possible target formation should occur in order to improve understanding of reservoir characteristics to increase EOR efficiency. Lithofacies preserved in the Tyler Formation illustrate meter-scale cyclical pattern. These cyclical patterns are characteristic of Carboniferous rocks found throughout North America. The cyclic nature of Carboniferous rocks are linked to the changing climatic conditions that resulted in sea-level changes during glaciation events in an icehouse world. Previous research has established a sequence stratigraphic framework for the Tyler Formation leading to improved temporal and spatial resolution. However, a weakly developed incised valley fill (IVF) has created problems in the correlation of the Tyler Formation in basinal settings. Correlation of genetic units using gamma ray log markers is possible for Tyler cycles across most of the basin. These markers are obscured near the basin edge where an IVF occurs in the lower part of the Tyler.

Widespread bulk and clay mineralogy has not yet been done on the Tyler Formation and this research precedes more advanced mineralogical work. The resulting work aims to improve cycle correlation within the Tyler Formation via association of units of similar mineralogical content. This work synthesized with gamma ray logs and sequence stratigraphy will provide a context on the southern edge of the basin for spatial variation of the diagenetic alteration and deposition with implications for EOR. This study may also provide new insight into understanding diagenetic evolution in relation to the IVF. Samples were taken from two cores across the basin for analysis of bulk mineral content as well as clay mineral content via x-ray diffraction (XRD). Preliminary data has given insight as to the interpretation of depositional environment and diagenetic episodes via the presence of mixed-layered clays in carbonaceous shale and kaolinite in palesols.