Frio brine sequestration pilot in the Texas Gulf Coast

A field experiment to pioneer CO2 injection for sequestration in a brine-bearing sandstone-shale sequence in the Texas Gulf Coast, USA, is in the preinjection modeling and planning phase. Innovations in this experiment include (1) CO2 injection into high-volume highpermeability rocks that have storage capacity sufficient to impact greenhouse gas emissions, (2) injection into a setting lacking the complications introduced by hydrocarbons and perturbations resulting from production and secondary recovery, and (3) intensive pre-, syn-, and post-injection monitoring and modeling for validation of the effectiveness of sequestration. The experiment is designed to provide a rapid increase in information from a small-volume and short-duration injection.Bureau of Economic Geolog

EOR as sequestration: Geoscience perspective

CO2 Enhanced Oil Recovery (EOR) has a development and operational history several decades longer than geologic sequestration of CO2 designed to benefit the atmosphere and provides much of the experience on which confidence in the newer technology is based. With modest increases in surveillance and accounting, future CO2 EOR using anthropogenic CO2 (CO2-A) captured to decrease atmospheric emissions can be used as part of a sequestration program.Bureau of Economic Geolog

Salt Caverns Studies - Regional map of Salt Thickness in the Midland Basin

Regional variation in the thickness of the major bedded salt-bearing interval of West Texas, the Salado Formation, serves as a screening criterion for distinguishing areas where the salt is heterogeneous, complex, and potentially less stable from areas where salt is more homogeneous. Areas with reduced and variable salt thickness and relatively shallow depths to the top of the salt are identified on the eastern shelf of the Midland Basin in Garza, Borden, Howard, Glasscock, and Reagan counties; along the Pecos River in Crockett, Upton, Crane, and Pecos Counties; and along the western edge of the Central Basin Platform in Ward and Winkler Counties. Initial data suggest that salt may be locally or regionally actively dissolving from these areas. Salt thinning is observed in areas where the top of salt is relatively deep (>1500 ft) south of the Matador Arch in Cochran, Hockley, and Lubbock counties, and locally along the eastern edge of the Central Basin Platform in Gaines, Andrews, and Ector Counties. This thinning is tentatively interpreted as predominantly resulting from deposition of thin salt or Permian salt dissolution. In all areas of thinning, sedimentary patterns suggest that facies changes may also influence the quality of the salt (salt purity, water content, bed thickness) over short distances. In other areas within the Midland and Delaware Basins, salt thickness changes occur gradually. However, the potential for local areas of salt dissolution, such as those beneath saline lakes, to impact the suitability of salt in these areas as host strata for cavern development, was not investigated in this regional study.Bureau of Economic Geolog

Carbon Capture and Geologic Sequestration from Intermittent Use of Fossil Fuels

Essentially all scenarios for reducing greenhouse gas emissions require deployment of a portfolio of mechanisms. In this paper, I consider the interactions among different emissions reductions methods focusing on how much flexibility in source-sink matching and intermittent operation is possible in Carbon capture and sequestration (CCS) methods. CCS is one of the mechanisms proposed to mitigate CO2 released from stationary sources. Much of the previous evaluation has focused on electricity generation from traditional base-load power plants, especially those that use coal as an energy source. This is reasonable for several reasons: flue gas from coal combustion has high CO2 concentrations, making post-combustion capture more efficient; coal has relatively high CO2 emissions per unit of energy, so that mitigation is needed; gasifiers and other chemical processes are widely used on coal, providing concentrated CO2 stream; and coal interest groups have organized programs to build “clean coal” programs in many regions. Coal has been widely used a base load power, with electricity from gas deployed as peak load. Planning a capture system to run as continuously as possible lowers cost per ton abated and per kilowatt generated and a stable system reduces design complexity and risk. However, shifting energy systems show that the assumption that CCS will be applied to base load coal power may be limited, and more complex scenarios are needed. In US markets low prices for natural gas have caused a shift from coal to natural gas. A system designed to reduce overall emissions by shifting dispatch away from the most carbon intensive facilities, such as the US Clean Power Plan seems likely to incentivize fuel switching from coal to natural gas. Changes in deployment of nuclear generation may also impact dispatch order. Further, deeper application of intermittent renewables, smart grid, and energy storage seem likely to have impacts on dispatch order and correspondingly drive needs for CCS to be used intermittently and on generators who are supplied with natural gas. Increasing use of natural gas also creates different non-combustion CO2 sources. Many unconventional gas sources have high CO2 impurities, which must be removed prior to market, therefore mitigation of this CO2 is part of the CCS picture. When natural gas is compressed to NLG, additional purification typically includes further lowering CO2. Traditionally use of CO2 for enhanced oil recovery is based on a steady stream from a natural source. CO2 from gas separation is also available in a steady stream, however the addition of gas resources will shift the location of mitigation regionally and internationally, including to offshore settings. If fossil-fuel-powered electricity generation is used to back-stop intermittent renewables, captured CO2 will be supplied only intermittently. An initial simplified study shows no harm to oil production from intermittent CO2 injection during EOR. The most significant impacts from intermittency would be from the need to oversize surface facilities to accept the high end of variable volumes of CO2. Further, the water-alternating- gas operation commonly used for EOR provides some confidence that intermittent CO2 injection would not be technically difficult. The impact of intermittency on capture operations may shift emphasis to lower CAPEX operations, and further study is needed

Quaternary Evolution of Playa Lakes on the Southern High Plains- A Case Study from the Amarillo Area

Playa lakes are abundant, small (generally <0.5 km in area) ephemeral lakes that occur in shallow (<11 m deep) depressions on the surface of the Southern High Plains. This study, based on analysis of excavations and 63 hollow-stem auger cores taken from 10 lakes in the study area around the Pantex Plant northeast of Amarillo, Texas, resolves long-standing controversies regarding origin, evolution, and recharge behavior of playa lakes. Origin of playa lakes has been debated for decades because the lakes are abundant but small, and the processes that form them are obscure. Although the ephemerally ponded playa lakes are floored by clay soils, ground-water and unsaturated-zone investigations show that playa lakes serve as sites of focused recharge. Description of a spectrum of playa basins of various sizes and recharge behaviors defines the similar characteristics and variable features in playa basins and documents the long-term maintenance of the seasonally ephemeral lakes and their responses to past climatic changes. These observations can be used to constrain assumptions that will be made about subsurface stratigraphy and recharge from the playas at the Pantex Plant.Bureau of Economic Geolog

Diagenesis of the San Andres Formation: Unit 4 Carbonate, G. Friemel and Detten Wells

Petrographic examination of 71 thin sections from the San Andres unit 4 carbonate reveals a complex diagenetic history. Diagenetic events include precipitation of calcite cement, neomorphic replacement of micrite by sparry calcite, development of moldic porosity, dolomitization, precipitation of halite and anhydrite, minor precipitation of celestite, and replacement of halite by calcite, dolomite, and anhydrite. Porous intervals are recognized within the San Andres unit 4 carbonate, corresponding to partly or completely dolomitized intervals. These diagenetic phases reflect an active history of changes in water composition, suggesting potential for further studies of rock-water relationships.Bureau of Economic Geolog

Investigation of water displacement following large CO2 sequestration operations

The scale of CO2 injection into the subsurface required to address CO2 atmospheric concentrations is unprecedented. Multiple injection sites injecting into multiple formations will create a large excess pressure zone extending far beyond the limited volume where CO2 is present. In a closed system, additional mass is accommodated by the compressibility of system components, an increase in fluid pressure, and possibly an uplift of the land surface. In an open system, as assumed in this analysis, another coping mechanism involves fluid flux out of the boundaries of the system, in which case the fresh-water-bearing outcrop areas, corresponding to the up-dip sections of the down-dip formations into which CO2 is injected, could be impacted. A preliminary study using a MODFLOW groundwater model extending far down-dip shows that injecting a large amount of fluid does have an impact some distance away from the injection area but most likely only in localized areas. A major assumption of this preliminary work was that multiphase processes do not matter some distance away from the injection zones. In a second step, presented in this paper, to demonstrate that a simplified model can yield results as useful as those of a more sophisticated multiphase-flow compositional model, we model the same system using CMG-GEM software. Because the chosen software lacks the ability to deal easily with unconfined water flow, we compare fluxes through time, as given by MODFLOW and CMG-GEM models at the confined/unconfined interface.Bureau of Economic Geolog

Characterization of Bedded Salt for Storage Caverns- A Case Study from the Midland Basin, Texas

The geometry of Permian bedded salt in the Midland Basin is a result of the interplay between depositional facies and post-depositional modification by salt dissolution. Mapping high-frequency cycle patterns in cross-section and map view using wireline logs helps document the salt geometry. Geologically based interpretation of depositional and dissolution processes offers a robust tool for mapping the geometry of salt to evaluate the suitability of sites for developing solution-mined storage caverns. Furthermore, this process-based description of salt geometry enhances the understanding of one of the most well-known sedimentary basins globally and can serve as a genetic model to aid in interpreting other salt basins. Solution-mined caverns in salt in the Midland Basin Salado Formation are cost-effective, large-volume storage facilities utilized for chemical feedstock. Caverns are also formed during salt dissolution to produce NaCl brine for drilling mud and other applications. More recently, solution-mined caverns have been employed for the disposal of oil-field wastes. This log-based regional analysis of salt character provides fundamental descriptive information on the geometry of salt necessary for siting and regulating the development, use, and decommissioning of these facilities, within the context of an exploration of facies relationships and implications for depositional history in this section of the Permian Basin.Bureau of Economic Geolog

What to do with CO2: The Knowns and Unknowns of Geologic Sequestration and CO2 EOR in Greenhouse Gas Context

Bureau of Economic Geolog

Monitoring and verification issues for carbon storage

Bureau of Economic Geolog