Date of Award
Master of Science - Geology
The Jurassic-aged Louann Salt is an evaporite sequence deposited in the Gulf of Mexico Basin (GOMB). It is an important component of the GOMB petroleum system and influences the facies pattern in overlying strata and the distribution of petroleum stratigraphic traps. The Louann Salt is composed primarily of halite with intercalated anhydrites and silty or sandy-halite intervals, with overall thicknesses in excess of four kilometers (~13,000 feet). Suture zones occur intermittently within the Louann Salt, formed by the collision of allochthonous evaporite layers. The mineralogy and geochemistry of the suture zones are currently understudied and can be hazardous during drilling operations, potentially causing over-pressurization of the zone. Furthermore, these evaporite bodies are potential sources for critical minerals or Rare Earth Elements, which can also lend insight into depositional conditions during the Jurassic.
The focus of this study was to determine the bulk geochemistry of the allochthonous evaporite layers within the Louann Salt in the Puma Field of the GOMB. Geochemical analyses were performed by handheld X-ray fluorescence (XRF) on approximately 600 cutting samples from the Puma West GC821-002 well, ranging from 2,057 meters to 6,528 meters (6,750 feet to 21,420 feet) below the surface. X-ray diffraction (XRD) analyses were conducted on ten samples within the suture zone to determine its mineralogy.
The results of the XRF analyses delineated the upper and lower boundaries of the Louann Salt by the inverse relationship between the chlorine and silicon elemental values. XRF analyses also indicate that the Louann Salt contains Rare Earth Elements (REEs) in the hundreds of part-per-million (ppm), such as Lanthanum (La), Praseodymium (Pa), Cerium (Ce), and Neodymium (Nd). REEs in the Louann are in concentrations equivalent to those being mined for economic value. XRD results indicate that the mineralogy of the suture zone is primarily composed of quartz, hematite, and smectite, with minor amounts of other clay minerals. This study provides insight into the depositional history of the Louann Salt and characteristics of the allochthonous bodies within the Louann for future mapping of the extent of these bodies in the GOMB.
Lesh, Brian, "Geochemical Characterization of the Louann Salt, Puma Field, Green Canyon, Gulf of Mexico Basin – Using XRF and XRD" (2022). Electronic Theses and Dissertations. 455.
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