January, 24 2018
The Mudrock Systems Research Laboratory
Annual Meeting will be held March 19th to 22nd
Monday the 19th will feature the core workshop.
Tuesday the 20th and Wednesday the 21st will be the oral and poster presentations.
Thursday the 22nd brings the Introduction to Mudrocks short course.
Please note that the meeting site will be slightly different this year, the talks on Tuesday and Wednesday will be held in the Research Office Complex Auditorium, just south of the main Bureau building. Bureau Directions and Maps.
January, 18 2018
Dr. Toti E. Larson
Geochmist / Chemical stratigraphy
The carbon cycle fundamentally controls how fossil fuels are stored and distributed in the Earth and is an important feedback system between the atmosphere, ocean and crustal rocks. Ultimately, the change of carbon fluxes (i.e., weathering, organic and carbonate burial, and upwelling) through time may have the most significant control on the spatial distribution of hydrocarbon deposits. From the view point of a geochemist: changes in carbon chemistry measured in drill cores offer important insights to the Earth’s carbon cycle through time, and are necessary to understand the complexities of unconventional resources.
I am currently developing new geochemical tools within the MSRL to collect high spatial resolution geochemical data from drill cores collected across mudrock and carbonate depositional systems. To the existing geochemistry facilities, I am adding sulfur isotope ratios, dolomite and natural gas isotope analysis. These data are used to define lateral changes in chemical facies across sedimentary basins, quantify depositional redox conditions along stratigraphic columns, develop global-scale oceanic chemistry models through time that can be used to correlate rock records across different basins, and help understand dolomite formation history.
My current research focuses on oceanic anoxic events (OAE’s) that are recorded throughout the Cretaceous Period. OAE’s reflect times when major changes in the Earth’s oceanic chemistry occurred and are typically recorded by the deposition of unconventional hydrocarbon deposits including the Eagle Ford and Niobrara Formation. To understand the onset of, and eventual recovery from OAE’s I am integrating high resolution X-ray fluorescence (XRF) major and trace data, and carbon isotope data for organic and inorganic fractions with numerical box model simulations. This approach is used to investigate how changes in oceanic carbon fluxes such as weathering input, oceanic circulation, and organic carbon deposition are recorded in the rock record locally, regionally, and globally. For example, within the Eagle Ford Formation we are using the relative timing between carbonate and organic carbon isotope excursions and shifts in trace element concentrations to understand the linkage between the collapse of the stable carbonate factory of the Comanche Platform, the deposition of the organic-rich Eagle Ford Formation, to the eventual recovery and deposition of the Austin Chalk.
December, 20 2017
In order to better realize our mission of providing top flight research to member companies, the Mudrock Systems Research Laboratory is seeking a Shale Sedimentologist/Stratigrapher to add to our group. So if you, or someone you know, wants to be part of the MSRL team, this is the time.
Duties include conducting basic and applied research in the characterization and interpretation of mudrock depositional systems. Also overseeing and coordinating data collection activities using microscopy, x-ray diffraction, and x-ray fluorescence analysis of facies. The successful candidate will interact with graduate students and present research findings at professional meetings and in print.
For further information and to apply:
UT Austin Job Posting - Research Associate | The University of Texas at Austin
October 11, 2017
New Publication: Reed, Robert M. (2017) Organic-matter pores: new findings from lower-thermal-maturity mudrocks. GCAGS Journal, v. 6, p. 99–110.
Available on the MSRL Members’ web page or at the Gulf Coast Association of Geological Societies web site.
About This Publication
Based on research presented at the 2016 MSRL meeting, this publication details findings on organic-matter pores in mudrocks with an Ro less than 0.7% from three locations in Texas. The article provides additional information on organic-matter pores that follows up on previous groundbreaking MSRL research on this subject (e.g. Loucks et al., 2009, 2012). MSRL researchers will continue efforts to understand the nature and distribution of this important type of mudrock pore.
New pore analyses of low-thermal-maturity (Ro < 0.7%) organic matter of possible or probable terrestrial origin (Type III kerogen) from three mudrock units in Texas contradict previous pore work on low-thermal-maturity, mostly marine organic matter from the Barnett and Eagle Ford Shales. In early work on mudrocks containing primarily marine organic matter, organic matter at Ro < 0.75% was observed to typically lack pores, whereas some thermally mature organic matter did develop pores. However, this pattern of pore development was not observed by all researchers working on other units, some of whom did see pores in organic matter at lower thermal maturities. To understand if predepositional pores in terrestrial organic matter are responsible for the discrepancy in pattern, this study focuses on organic matter at low thermal maturities, which should not have thermally generated pores.
Two beds of organic-matter-rich mudrock from a terrestrial depositional environment were sampled from the Paleogene Wilcox Group of East Texas. The mudrocks have an Ro of < 0.5%, a siliceous–argillaceous composition, and > 11% total organic carbon (TOC). Based on Rock-Eval pyrolysis results and depositional setting, the kerogen is thought to be dominantly Type III. Some silt-sized organic-matter grains in these samples contain probable predepositional pores. Pore sizes are up to 5 µm in length, and up to 27% of the organic matter has pores. Pores are more common in the larger organic-matter grains.
Samples from one core interval of the basal Cretaceous Eagle Ford Group on the San Marcos Arch of South Texas have abundant vitrinite (Ro ~ 0.45%) based on visual analysis, in contrast with shallower layers, which are vitrinite-poor. Rock-Eval pyrolysis results suggest the presence of Type III kerogen. Although these basal mudrock samples are more argillaceous than the rest of the Eagle Ford, they were deposited in a marine environment. Some of the organic matter in these samples has predepositional pores. Some of these pores are elongate, with sizes > 1 µm.
Pennsylvanian Smithwick Shale samples from the Fort Worth Basin of Texas have thermal maturity ranging from 0.4 to 0.71% Ro. Although much of the unit is marine, observed plant fossils suggest a mixed-organic-matter source. Some Rock-Eval pyrolysis results also suggest Type III kerogen. Much of the organic-matter shows a newly identified organic-matter pore texture. Instead of consisting of a mass of organic matter with spherical holes, the organic-matter is a composite grain made up of smaller, spherical organic-matter bodies. These organic-matter bodies vary slightly in size, but most are 60 to 100 nm in diameter. Pore space is present between the organic-matter bodies. Several possible formation mechanisms exist for these organic-matter bodies, but they strongly resemble “nannobacteria” described by previous researchers.
March 8, 2017
March 1, 2017
VIDEO: Meet The Author: Robert Baumgardner discusses RI 281. (6 minutes)
To purchase this publication as a (PDF) download, please order RI0281D ($15.00).
About This Publication
This report, conceived as a follow-up to regional treatment of the Wolfberry depositional systems in Report of Investigations No. 277, focuses on basinal facies of the lower Leonard and Wolfcamp intervals in the southern Midland Basin. The report provides detailed lithologic information about mudrocks and associated facies that were largely ignored before they became prolific producers of hydrocarbons as a result of hydraulic fracturing and horizontal drilling. Readers interested in the regional view presented in RI 277, and those seeking detailed lithologic information about the so-called Wolfcamp A and B zones, should find value in the core-based descriptions of lithofacies in this report, which examines the most continuous basinal cores publicly available from the Lower Permian/Upper Pennsylvanian interval in the Midland Basin. Detailed core description (including thin-section analysis)—combined with total organic carbon (TOC) sampling, handheld XRF scanning, and micro-rebound hammer testing at 1-ft spacing (techniques applied to these cores for the first time)—reveals significant, facies-related differences in TOC content, mineralogy, and rock strength. In addition, programmed pyrolysis (Rock-Eval®) analysis reveals that most kerogen in the lower Leonard/Wolfcamp interval is in the oil-production window and has matured to Type II–III (“oil-gas prone”). Stratigraphers as well as explorationists will find information here to improve their understanding of Permian-age basinal mudrocks in the Midland Basin.
Basinal mudrocks and associated facies assigned to the Wolfcamp and lower Leonard lithostratigraphic units in the Midland Basin are prolific producers of oil and gas. Four facies are recognized in core on the basis of macroscopic examination, XRD analysis, and ED-XRF elemental chemistry: (1) siliceous mudrock, (2) calcareous mudrock, (3) muddy bioclast–lithoclast floatstone, and (4) skeletal wackestone/packstone. Mudrocks are largely hemipelagic deposits of fine-grained sediment delivered by suspension settling. Floatstones were deposited by debris flows that originated on carbonate shelves around the basin. Wackestones/packstones are finer grained sediment density-flow deposits, probably turbidites, reworked by local bottom currents. These sediments were deposited below storm wave base in a basin having limited connection to the open ocean. During deposition, low-oxygen conditions prevailed in bottom waters and sediments, as shown by the presence of agglutinated foraminifera, rarity of burrows, widespread prevalence of small (<6 μm) pyrite framboids, presence of phosphatic nodules, and elevated molybdenum concentrations. Total organic carbon (TOC) content reaches 6.8 percent. TOC is facies-dependent (highest in siliceous mudrock) and varies widely within small vertical distances. Cyclicity is evident in individual meter-thick, upward-fining cycles of floatstone or wackestone/packstone overlain by calcareous and siliceous mudrock. Rock strength increases as calcite content increases, likely as a result of diagenetic cementation. Most kerogen in the lower Leonard–Wolfcamp interval is in the oil-production window and has matured to Type II–III (“oil–gas prone”). On the basis of their TOC and hydrogen content, siliceous mudrocks have the highest potential for hydrocarbon generation.
Keywords: basinal mudrocks, cyclicity, organic matter, Pennsylvanian, Permian, Reagan County, Rock-Eval®, rock strength, stratigraphy