Theses and Dissertations at Montana State University (MSU)
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Item A thermochronological history of burial and exhumation at Kevin Dome, Northwest Montana including the origin of CO2 in Upper Devonian Duperow Formation and the Bakken Petroleum system at the Dome(Montana State University - Bozeman, College of Letters & Science, 2022) Adeniyi, Elijah Olusola; Chairperson, Graduate Committee: Mary S. Hubbard; This is a manuscript style paper that includes co-authored chapters.Kevin Dome is a geologic structure and historic hydrocarbon producer in northwest Montana. This structure is also a known CO 2 reservoir, yet its development has not been constrained with thermochronological techniques and the origin of the natural (~ 283 x 109 m 3) CO 2, of the Upper Devonian Duperow Formation, is not well understood. This work seeks to create a temporal understanding of the burial and exhumation history of Kevin Dome including the hydrocarbon generation and CO 2 emplacement. I constrained the burial and exhumation history at Kevin Dome with low-temperature thermochronology, carbonate clumped isotope thermometry, and thermobarometric proxies. I also tested for microbial, thermogenic, and magmatic CO 2 source(s) as well as CH 4 and N 2 gas sources at the dome with major gas composition, stable and noble gas isotopic geochemistry methods. I found that Kevin Dome rocks were buried to oil and gas generation windows before exhumation during the Late Cretaceous-Paleocene (~65 - 72Ma) and the Oligocene-Miocene (~ 15 - 26Ma) at an average rate of ~ 0.27 mm/yr. My study supports an evolved forebulge-dome origination model for Kevin Dome that is driven by the Late Cretaceous-Paleocene emplacement of the Rocky Mountain overthrust in a Foreland Basin setting in northwestern Montana (and proximal Canada) and an Oligocene-Miocene erosional or epeirogenic event not previously recognized in northwest Montana. I estimated ~4 - 5 km more overburden erosion than was previously thought in the region and suggest that the Oligocene-Miocene exhumation terminated hydrocarbon generation at Kevin Dome. In terms of CO 2 origin, my data supports a magmatic origin for the Duperow CO 2, with emplacement during the Sweetgrass Hills igneous complex intrusion(~52 Ma). I also found that the CH4 and N2 gases at Kevin Dome were mainly thermogenic in origin. A CO 2 solubility model showed that ~98% of the CO 2 has been dissolved into the groundwater in the Bakken petroleum system's hydrocarbon-bearing reservoirs at Kevin Dome during migration. I present a novel approach of integrating modern t-T sensitive techniques, stratigraphy, thermal maturity data, and isotopic geochemistry to address the structural development of sedimentary basins/domes, hydrocarbon generation, and magmatic CO 2 emplacement and subsequent evolution.Item Fracture analysis of Little Sheep Mountain anticline, eastern Bighorn Basin, Wyoming : structural controls on fluid migration through a fault-controlled Laramide structure(Montana State University - Bozeman, College of Letters & Science, 2015) Kay, Lauren Marie; Chairperson, Graduate Committee: David LagesonLittle Sheep Mountain is a doubly-plunging asymmetric anticline in the northeastern Bighorn Basin, Wyoming. Anticlines in the basin provide subsurface structural traps for oil and natural gas, several of which produce from the Mississippian Madison Formation, a world-class fractured carbonate reservoir. Little Sheep Mountain anticline has been uplifted and the hydrocarbon trap has been breached by erosion, exposing reservoir rocks analogous to these proximal subsurface structures. An outcrop-scale investigation of fracture geometry and geochemical analysis of breccia bodies in the anticline provides insight into the history of fluid migration and structurally-controlled diagenesis within the anticline. A combination of field techniques and analytical methods were used to characterize the relationship between fracture patterns and subsurface paleofluid migration. Field-based analyses of fractures and breccias were conducted to characterize structural elements of the anticline with respect to fluid flow. Geochemical analysis was used to constrain the origin and migration history of paleofluids. Diagenetic characteristics and alteration associated with fluid migration within the fracture network were examined using strontium and stable isotopes in conjunction with petrography. Faulting related to Laramide deformation has led to extensive fracturing and brecciation in Little Sheep Mountain anticline. Fracture network geometry was identified as a major control on fluid migration within the structure that has provided conduits for episodic hydrothermal fluid flow. Progressive deformation during Laramide fold growth maintained and enhanced fluid flow networks and locally enhanced porosity. Mississippian-age collapse breccia bodies were identified as preexisting weak horizons for focused hydrothermal fluid flow during the Laramide. Low-temperature hydrothermal mineralization resulting from episodic fluid flow led to complex diagenetic alteration. Fracture sets parallel to and perpendicular to the Laramide shortening direction acted as primary fluid flow conduits within Little Sheep Mountain anticline and provided enhanced porosity and permeability in the subsurface reservoir rocks. Hydrothermal breccia bodies represent discrete vertical fluid conduits controlled by fracture geometry through which hydrothermal fluids migrated. Brecciation associated with Laramide deformation and late-stage diagenetic alteration was found to generally reduce the porosity of Madison reservoir rocks adjacent to breccia bodies by the infilling of fractures and occlusion of pores with late-stage calcite cement.