Rebecca C. Smyth

Regional controls on geomorphology, hydrology, and ecosystem integrity in the Orinoco Delta, Venezuela

Interacting river discharge, tidal oscillation, and tropical rainfall across the 22,000 km2 Orinoco delta plain support diverse fresh and brackish water ecosystems. To develop environmental baseline information for this largely unpopulated region, we evaluate major coastal plain, shallow marine, and river systems of northeastern South America, which serves to identify principal sources and controls of water and sediment flow into, through, and out of the Orinoco Delta. The regional analysis includes a summary of the geology, hydrodynamics, sediment dynamics, and geomorphic characteristics of the Orinoco drainage basin, river, and delta system. Because the Amazon River is a major source of sediment deposited along the Orinoco coast, we summarize Amazon water and sediment input to the northeastern South American littoral zone. We investigate sediment dynamics and geomorphology of the Guiana coast, where marine processes and Holocene history are similar to the Orinoco coast. Major factors controlling Orinoco Delta water and sediment dynamics include the pronounced annual flood discharge; the uneven distribution of water and sediment discharge across the delta plain; discharge of large volumes of water with low sediment concentrations through the Rio Grande and Araguao distributaries; water and sediment dynamics associated with the Guayana littoral current along the northeastern South American coast; inflow of large volumes of Amazon sediment to the Orinoco coast; development of a fresh water plume seaward of Boca Grande; disruption of the Guayana Current by Trinidad, Boca de Serpientes, and Gulf of Paria; and the constriction at Boca de Serpientes.

Mud volcanoes of the Orinoco Delta, Eastern Venezuela

Abstract Mud volcanoes along the northwest margin of the Orinoco Delta are part of a regional belt of soft sediment deformation and diapirism that formed in response to rapid foredeep sedimentation and subsequent tectonic compression along the Caribbean–South American plate boundary. Field studies of five mud volcanoes show that such structures consist of a central mound covered by active and inactive vents. Inactive vents and mud flows are densely vegetated, whereas active vents are sparsely vegetated. Four out of the five mud volcanoes studied are currently active. Orinoco mud flows consist of mud and clayey silt matrix surrounding lithic clasts of varying composition. Preliminary analysis suggests that the mud volcano sediment is derived from underlying Miocene and Pliocene strata. Hydrocarbon seeps are associated with several of the active mud volcanoes. Orinoco mud volcanoes overlie the crest of a mud-diapir-cored anticline located along the axis of the Eastern Venezuelan Basin. Faulting along the flank of the Pedernales mud volcano suggests that fluidized sediment and hydrocarbons migrate to the surface along faults produced by tensional stresses along the crest of the anticline. Orinoco mud volcanoes highlight the proximity of this major delta to an active plate margin and the importance of tectonic influences on its development. Evaluation of the Orinoco Delta mud volcanoes and those elsewhere indicates that these features are important indicators of compressional tectonism along deformation fronts of plate margins.

Mapping coastal environments with lidar and EM on Mustang Island, Texas, U.S.

We explore whether lidar (light detection and ranging) and EM (electromagnetic induction) can improve the accuracy and resolution of wetland mapping that has historically been based chiefly on analysis of aerial photographs. Using Mustang Island on the central Texas coast as an example, we exploit (1) the known strong relationship between elevation and coastal habitat by comparing a lidar-derived digital elevation model (DEM) with existing wetland maps and detailed vegetation transects, and (2) another known strong relationship between soil and water salinity and coastal habitat by collecting and comparing EM-derived conductivity data with elevation and vegetation type across the island.

Chemical and thermal zonation in a mildly alkaline magma system Infiernito Caldera, Trans-Pecos Texas

Postcollapse lavas of the Infiernito caldera grade stratigraphically upward from nearly aphyric, high-silica rhyolite (76% SiO2) to highly prophyritic trachyte (62% SiO2). Plagioclase, clinopyroxene, orthopyroxene, magnetite, ilmenite, and apatite occur as phenocrysts throughout the sequence. Sanidine, biotite, and zircon are present in rocks with more than about 67% SiO2. Major and trace elements show continuous variations from 62 to 76% SiO2. Modeling supports fractional crystallization of the observed phenocrysts as the dominant process in generating the chemical variation.Temperatures calculated from coexisting feldspars, pyroxenes, and Fe-Ti oxides agree and indicate crystallization from slightly more than 1100° C in the most mafic trachyte to 800° C in high-silica rhyolite. The compositional zonation probably arose through crystallization against the chilled margin of the magma chamber and consequent rise of more evolved and therefore less dense liquid.Mineral compositions vary regularly with rock composition, but also suggest minor mixing and assimilation of wall rock or fluids derived from wall rock. Mixing between liquids of slightly different compositions is indicated by different compositions of individual pyroxene phenocrysts in single samples. Liquid-solid mixing is indicated by mineral compositions of glomerocrysts and some phenocrysts that apparently crystallized in generally more evolved liquids at lower temperature and higher oxygen fugacity than represented by the rocks in which they now reside. Glomerocrysts probably crystallized against the chilled margin of the magma chamber and were torn from the wall as the liquid rose during progressive stages of eruption. Assimilation is indicated by rise of oxygen fugacity relative to a buffer from more mafic to more silicic rocks.Calculation of density and viscosity from the compositional and mineralogical data indicates that the magma chamber was stably stratified; lower temperature but more evolved, thus less dense, rhyolite overlay higher temperature, less evolved, and therefore more dense, progressively more mafic liquids. The continuity in rock and mineral compositions and calculated temperature, viscosity, and density indicate that compositional gradation in the magma chamber was smoothly continuous; any compositional gaps must have been no greater than about 2% SiO2.

Assessing impacts to groundwater from CO2-flooding of SACROC and Claytonville oil fields in West Texas

Comparison of groundwater above two Permian Basin oil fields (SACROC Unit and Claytonville Field) near Snyder, Texas should allow us to assess potential impacts of 30 years of CO2-injection. CO2-flooding for enhanced oil recovery (EOR) has been active at SACROC in Scurry County since 1972. Approximately 13.5 million tons per year (MtCO2/yr) are injected with withdrawal/recycling amounting to ~7MtCO2/yr. It is estimated that the site has accumulated more than 55MtCO2; however, no rigorous investigation of overlying groundwater has demonstrated that CO2 is trapped in the subsurface. Mineralogy of reservoir rocks at the Claytonville field in southwestern Fisher County is similar to SACROC. CO2-EOR is scheduled to begin at Claytonville Field in Fisher County in early 2007. Here we have the opportunity to characterize groundwater prior to CO2-injection and establish baseline conditions at Claytonville. Methods of this study will include: (1) examination of existing analyses of saline to fresh water samples collected within an eight-county area encompassing SACROC and Claytonville, (2) additional groundwater sampling for analysis of general chemistry plus field-measured pH, alkalinity, and temperature, stable isotopic ratios of hydrogen (D/H), oxygen (O/O), and carbon (C/C), and (3) geochemical equilibrium and flowpath modeling. Existing groundwater data are available from previous BEG studies, Texas Water Development Board, Kinder Morgan CO2 Company, and the U. S. Geological Survey. By examining these data we will identify regional groundwater variability and focus additional sampling efforts. The objective of this study is to look for potential impacts to shallow groundwater from deep CO2-injection. In the absence of conduit flow from depth, we don’t expect to see impacts to shallow groundwater, but methodology to demonstrate this to regulators needs to be established. This work is a subset of the Southwest Regional Partnership on Carbon Sequestration Phase 2studies funded by the Department of Energy (DOE) in cooperation with industry and government partners. Biographical Sketches Rebecca C. Smyth holds an M. A. in geology (specialty in hydrogeology) from University of Texas at Austin and is a registered professional geologist in the State of Texas. Over the past 10 years at BEG her work has included groundwater impact studies related to oil and gas exploration and production throughout Texas and elevated levels of arsenic in south Texas. Mark H. Holtz has more than 20 years of reservoir characterization experience at the BEG. He has focused on integration of geology and engineering in both carbonate and siliciclastic oil and gas reservoirs throughout the U.S. Gulf Coast, the Australian Cooper and Eromanga Basins, the Vienna Basin, Venezuela, Argentina, and Mexico. Stephen N. Guillot is Senior Reservoir Engineer for Kinder Morgan CO2 Co. LP. He is managing Kinder Morgan’s industry support of Southwest Regional Partnership for Carbon Sequestration research studies at the SACROC Unit and Claytonville Field east of Snyder, Texas. BEG SWCARB Project Assessing Impacts to Groundwater from CO2-flooding of SACROC and Claytonville Oil Fields in West Texas Rebecca C. Smyth, Mark H. Holtz, and Stephen N. Guillot with acknowledgments to: Jean-Philippe Nicot, Susan D. Hovorka, and others Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin and Kinder Morgan CO2 Company L.P., Houston, Texas BEG SWCARB Project Overview of Hydrogeologic Study • Eight county study area encompasses SACROC (Scurry Area Canyon Reef Operations Committee) Unit and Claytonville fields in west Texas, • Physical and chemical data sources on groundwater (fresh to saline) include: previous BEG studies, Texas Water Development Board (TWDB), Kinder Morgan CO2, and U. S. Geological Survey, • Identify regional variability in physical and hydrogeochemical properties of groundwater from existing analyses, • Conduct additional sampling for major ion, total organic carbon, stable isotopes of hydrogen (D/H), oxygen (18O/16O), and carbon (13C/12C); pH, temperature, and alkalinity field measurements, might install two new water wells in Claytonville, • Look for geochemical evidence of mixing starting with simple approach: decreased pH, decreased temperature, ion plots, • Geochemical equilibrium and flowpath modeling to identify groundwater mixing. Models being considered include: PHREEQC, SOLMNEQ.88, EQ3/EQ6, Geochemist’s Workbench. BEG SWCARB Project Background • SMALL subset of Southwest Regional Partnership on Carbon Sequestration Phase 2 studies funded by Department of Energy (DOE) in cooperation with industry (Kinder Morgan CO2) and government (New Mexico Tech, and LANL) partners. BEG water portion is a four-year project (50% time years 1&2, 25% time years 3&4). • Since 1972, ~13.5 million tons per year (MtCO2/yr) injected at SACROC with withdrawal and recycling amounting to ~7MtCO2/yr. Estimated that site has accumulated more than 55MtCO2. • CO2 sources in southwestern Colorado and northern New Mexico for which there are stable isotopic data available in literature. BEG SWCARB Project Kinder Morgan CO2 Assets

COMBINING EM AND LIDAR TO MAP COASTAL WETLANDS: AN EXAMPLE FROM MUSTANG ISLAND, TEXAS

We combined airborne lidar and ground-based EM induction measurements with vegetation surveys along two transects across Mustang Island, a barrier island on the Texas coast, to examine whether these methods can be used to map coastal wetlands and associated geomorphic environments. Conductivity varied inversely with elevation along both transects. Elevation and conductivity profiles correlated reasonably well with habitat mapped in the largely imagery-based 1992 National Wetland Inventory (NWI), but they possessed greater detail and identified misclassified habitat. Detail achievable with elevation and conductivity data was similar to that achieved in on-the-ground vegetation surveys. Lowest elevations and highest conductivities were measured in saline environments (marine and estuarine units, forebeach, salt marsh, and wind-tidal flats). Highest elevations and lowest conductivities were measured in nonsaline environments (upland and palustrine units, dunes, vegetated-barrier flats, and fresh marsh). Elevation and conductivity data allow better discrimination among coastal wetland and geomorphic environments than can be achieved from image interpretation alone. Future work should include evaluating the effect of vegetation density on lidar-beam penetration, quantifying seasonal change in ground conductivity in fresh and saline coastal environments, examining the geographic variability of elevation and conductivity statistics, and evaluating the use of airborne EM sensors to measure ground conductivity at multiple exploration depths.

Best Management Practices for subseabed geologic sequestration of carbon dioxide

A team led by the Gulf Coast Carbon Center at the Bureau of Economic Geology, Jackson School of Geosciences at The University of Texas at Austin, has been funded by the National Oceanographic Partnership Program (NOPP) through and in cooperation with the U.S. Department of Interior (DOI), Bureau of Ocean Energy Management (BOEM) to generate a Best Management Practices (BMPs) document on sub-seabed geologic sequestration of carbon dioxide (CO2) below the U.S. outer continental shelf. The team consists of scientists, engineers, lawyers, and business managers from academia, private industry, and State of Texas government from the following institutions: (1) Gulf Coast Carbon Center at the Bureau of Economic Geology (BEG), (2) Det Norske Veritas (USA) Inc (DNV), (3) Wood Group Mustang and sister company Wood Group Kenny (Wood Group), (4) Texas General Land Office (GLO), (5) Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi (HRI), and (6) The University of Houston Law Center. Individual team members have expertise in carbon sequestration monitoring, CO2-pipeline design and construction, and domestic and international offshore environmental policy. The BMPs will be reviewed by external experts after it is generated and before being submitted to BOEM. The purpose of the BMPs will be to provide technical guidance to BOEM and BSEE (U.S. DOI Bureau of Safety and Environmental Enforcement) to establish regulatory guidelines for offshore components of future U.S. Carbon Capture and Storage, which is sometimes referred to as sequestration, (CCS) industry. Sub-seabed geologic sequestration (GS) is the process whereby CO2 captured from large volume industrial sources (e.g., power plants, oil refineries) will be (1) compressed to supercritical state and transported via pipeline to offshore injection wells, and (2) injected into geologic strata deep (thousands of feet) below the seafloor. Objectives of the CO2 injection will be for “pure sequestration” (i.e., long-term storage of CO2 in subseafloor saline reservoirs) or sequestration combined with enhanced oil recovery (EOR). Sub-seabed geologic sequestration is very different from ocean dumping (i.e. dissolution of CO2 into circulating seawater) or injection of CO2 into deep water, shallow sub-seabed sediments. Some researchers proposed in the past that shallow subseafloor depths (<; 1,000 ft) were sufficient for permanent CO2 storage in deep marine environments (>; 11,000 ft water depth) (e.g., House et al., 2006). However, the shallow sedimentary subseafloor environment could become unstable and allow release of CO2 into ocean water, the end result of which would be ocean dumping. One mechanism of seafloor instability could be the release of gas from hydrates owing to pressure and temperature perturbations that may be introduced by shallow drilling and CO2 injection. Furthermore, the logistics of transporting CO2 hundreds of miles offshore to areas with sufficient water depths for storage in shallow subsea sediments would probably not be economically feasible. We want to emphasize that subseabed GS of CO2 is not ocean dumping. One of the biggest concerns for onshore GS is the potential to impact shallow drinking water resources. Injecting CO2 deep below the seafloor will avoid this potential consequence. But there are sensitive marine environments of concern in offshore settings, protection of which is critical. Environmental monitoring of marine ecosystems (nearshore, along CO2 pipeline corridors, and outer continental shelf) and subseafloor geological strata in which CO2 will be injected will be a large component of the BMPs. Topics being included in the BMPs, a draft of which will be submitted to BOEM in June of 2013, are: (1) site selection and characterization, (2) risk analysis, (3) project planning and execution, (4) environmental monitoring, (5) mitigation, (6) inspection and auditing, (7) reporting requirements, (8) emergency response and contingency planning, (9) decommissioning and site closure, and (10) legal issues. Where possible, we are using existing regulatory, policy, and technical guidance documents as a starting point for the BMPs. We think the most likely location for initiation of U.S. offshore geologic sequestration of CO2 will be in the western or central sectors of the Gulf of Mexico where extensive offshore oil and gas infrastructure already exists. Academic members of our project team are actively working on criteria for site selection [1]. However, private industry is also assessing the feasibility of offshore geologic sequestration below the Atlantic seafloor [2].

Potential Sinks for Geologic Storage of CO2 Generated in the Carolinas

Duke Energy, Progress Energy, Santee Cooper Power, South Carolina Electric and Gas, Electric Power Research Institute (EPRI), Southern States Energy Board (SSEB)