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dc.contributor.advisorSonnenberg, Stephen A.
dc.contributor.authorBlake, Jenny A.
dc.date.accessioned2020-06-07T10:13:27Z
dc.date.accessioned2022-02-03T13:21:17Z
dc.date.available2020-12-04T10:13:27Z
dc.date.available2022-02-03T13:21:17Z
dc.date.issued2020
dc.identifierBlake_mines_0052N_11936.pdf
dc.identifierT 8916
dc.identifier.urihttps://hdl.handle.net/11124/174125
dc.descriptionIncludes bibliographical references.
dc.description2020 Spring.
dc.description.abstractThe Leonardian Bone Spring Formation and associated Avalon Shale member are significant producers of oil, gas, and condensate in the Delaware Basin of southeast New Mexico and west Texas. The Bone Spring represents a mixed siliciclastic-carbonate succession deposited as sediment gravity flows under cyclical sea level fluctuations. Quiet, pelagic deposition of organic matter occurred in the deep basin which allowed for the accumulation of organic-rich mudstones. These quiet settling periods were interrupted by high-energy clastic episodes that deposited the interbedded carbonates and sandstones that characterize these formations. Based on the alternating layers of siliciclastics and carbonates, the Bone Spring Formation is subdivided into three main units; from shallow to deep these are the 1st Bone Spring, 2nd Bone Spring, and 3rd Bone Spring. Each of these units is further delineated into an underlying sandstone interval and an overlying carbonate interval. The Avalon Shale lies within the 1st Bone Spring Carbonate. The aims of this study are to provide an understanding on how mineralogy, depositional processes, depositional environment, and diagenesis affect reservoir quality and source potential of the Avalon Shale and 1st Bone Spring Formation in the lesser-explored southern Delaware Basin. Five cores from three wells in southern Reeves and western Pecos are used. Two cores are from the Avalon, one is from the 1st Bone Spring Carbonate, and two are from the 1st Bone Spring Sand. The highly heterolithic nature of the Avalon and 1st Bone Spring formations warrants an integrated, multiscale approach in order to properly characterize their source and reservoir potential. The incorporation of core, XRD, XRF, petrographic thin section, and FE-SEM analyses has enabled the identification of lithofacies across multiple scales. Eleven lithofacies comprising four facies groups were identified. Reservoir quality of each facies group and lithofacies was established through core-based measurements of source rock and reservoir property analyses. Three primary reservoir facies and three secondary reservoir facies were identified.The three primary reservoir facies are the three facies that comprise the Siliceous Facies Group: (1) argillaceous siliceous mudstone, (2) argillaceous siliceous siltstone, and (3) spiculitic siliceous mudstone. XRD analysis shows that they contain the highest percentages of silicate minerals (quartz + feldspars + micas; QFM) (65 avg. wt.%) and clay (24 avg. wt.%) with the lowest amounts of carbonates (4.5 avg. wt.%). These Siliceous Facies are organic-rich with TOCs averaging 3.8 wt.%. Crushed rock analyses indicate average porosities and permeabilities of 5.2% and 354 nD, respectively. Additionally, these facies are the most abundant, totaling 69% of the five cores utilized in this study.The three secondary reservoir facies form the Mixed Siliceous Facies Group: (1) radiolarian-rich siliceous siltstone, (2) calcareous siliceous siltstone, and (3) skeletal-rich siliceous mudstone. Compared to the Siliceous Facies, XRD analyses indicates slightly decreased QFM (53.5 avg. wt.%) and clay (16.7 avg. wt.%) contents coupled with an increase in carbonate minerals (22.7 avg. wt.%). The Mixed Siliceous Facies contain lower values of TOC (2.85 avg. wt.%) and display variable porosities and permeabilities with an average of 4.19% and 141 nD, respectively. Another factor contributing to their classification as secondary reservoir facies is the fact that they are less prevalent, only comprising 11% of the cores used in this study.Mineralogy was found to affect the source and reservoir quality of a rock. Increases in quartz and clay contents show a positive correlation with increases in TOC, porosity, and permeability, while increases in carbonate content have a negative effect on these properties. Carbonate diagenesis, commonly in the form of calcite precipitation, is often seen negatively impacting reservoir quality.The source of silica also plays an important role on reservoir quality. Petrographic analyses and elemental cross plots reveal that detrital, biogenic, and authigenic sources of silica exist within the Avalon and 1st Bone Spring formations. Prolific abundances of siliceous radiolaria and sponge spicules observed in thin section and under FE-SEM provide the silica source for precipitation of microcrystalline quartz. Typically, authigenic quartz is known to preserve porosity and increase brittle behavior. However, it appears that pore-filling authigenic calcite precipitated prior to the formation of microcrystalline quartz, which may have prevented much of the original porosity from being preserved. Furthermore, while nearly all intervals display brittle tendencies, quartz contents are only found to significantly impact mineral brittleness indices when QFM contents are ≥ 50 wt.%.Source rock analysis indicates that the Avalon and 1st Bone Spring predominantly contain oil-prone Type II kerogen in the early to peak oil window. The formations exhibit excellent source rock potential due to their high TOCs; good S1 and S2 values, which suggest that hydrocarbons have already been generated and will continue to be generated; and their thermal maturity and fluid type indicators suggestive of oil generation.Petrophysical models were created in order to get a better understanding of the source and reservoir quality of the Avalon and 1st Bone Spring and include: upscaled log facies, organic richness (TOC), water saturation, and brittleness. Integration of core and log data allowed for the geologic reservoir characterization of the formations at a larger scale within the study area. The properties that most impact reservoir quality are examined and include: composition, organic richness, porosity, permeability, fluid saturations, and brittleness. Overall, the Avalon and 1st Bone Spring display good source and reservoir characteristics in the southern Delaware Basin. Siliceous zones with increased porosities and low water saturations show especially high reservoir potential. Finally, the Avalon in the study area is compared to the Avalon in the shale’s core-producing region in Lea County, New Mexico. Core data indicates that the Avalon is less mature in the southern Delaware Basin compared to the northern portion of the basin. This may explain why development is currently focused in this region; however, the similar compositions, greater organic contents, and maturities indicative of oil generation all suggest that the Avalon has excellent source and reservoir potential in the southern Delaware Basin.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2020 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectBone Spring
dc.subjectPermian Basin
dc.subjectAvalon
dc.subjectreservoir characterization
dc.subjectDelaware Basin
dc.titleGeologic reservoir characterization of the Avalon shale and 1st Bone Spring formation in the southern Delaware Basin
dc.typeText
dc.contributor.committeememberFrench, Marsha
dc.contributor.committeememberJobe, Zane R.
dcterms.embargo.terms2020-12-04
dcterms.embargo.expires2020-12-04
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineGeology and Geological Engineering
thesis.degree.grantorColorado School of Mines
dc.rights.accessEmbargo Expires: 12/04/2020


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