Expert-based development of a standard in CO2 sequestration monitoring technology

Bureau of Economic Geolog

Real-scale investigation of the kinematic response of a rockfall protection embankment

This paper addresses the response of rockfall protection embankments when exposed to a rock impact. For this purpose, real-scale impact experiments were conducted with impact energies ranging from 200 to 2200 kJ. The structure was composed of a 4m high cellular wall leaned against a levee. The wall was a double-layer sandwich made from gabion cages filled with either stones or a sand–schreddedtyre mixture. For the first time, sensors were placed in different locations within the structure to measure real-time accelerations and displacements. The test conditions, measurement methods and results are presented in detail. The structure’s response is discussed in a descriptive and phenomenological approach and compared with previous real-scale experiments on other types of embankments

Geographical, Geological, and Hydrogeological Attributes of Formations in the Footprint of the Eagle Ford Shale

This document provides an overview of the geological characteristics of formations within the footprint of the South Texas Eagle Ford (EF) Shale play, with a particular focus on water. The EF play, spanning approximately 25 counties, has experienced significant development in recent years, with expansion into additional counties to the north. Despite its recent growth, the EF area has a long history of oil and gas exploration and production, with over 110,000 wells drilled in the past century, excluding the approximately 5,000 EF wells as of March 2013. The EF shale serves as a source rock, supplying oil and gas to reservoirs such as the Big Well, Pearsall fields, and the Giddings field. While predominantly rural, the EF area encompasses several large cities such as San Antonio and Laredo, which border its edges. This document focuses on two key aspects of hydraulic fracturing (HF) in the EF play: water use and water disposal. The South Texas location of the play, coupled with its limited surface water resources, intensifies perceived conflicts with other water users. The significant depth of the folded Paleozoic basement beneath the EF (exceeding 15,000 ft) allows for a thick sediment sequence of Jurassic and younger age. Positioned in the middle of this sequence (approximately 4,000 to 11,000 ft deep), the EF shale is separated from the ground surface by numerous formations, including the Midway Clay. This geological setup provides multiple horizons for fluid disposal. The thickness of the EF varies from approximately 100 ft east of Austin to over 500 ft at the Mexican border. The sedimentary sequence above the basement initially comprises carbonate-rich formations such as the Edwards, Glenrose, and Austin Chalk formations, with the EF itself being a carbonate mudrock. Towards the end of the Cretaceous period, the succession transitions to siliciclastic formations characterized by alternating sandstones and claystones deposited in fluvial and/or deltaic environments. Some sand-rich intervals within this succession form freshwater aquifers in the EF footprint, including the Carrizo aquifer, as well as other aquifers of lesser water quality such as the Wilcox and Yegua-Jackson aquifers. Shallow subsurface water tends to be brackish outside of the aquifer outcrop areas. In 2011, water use in the EF play amounted to approximately 24 thousand acre-feet (AF). The top HF users in the EF during that year were Webb (4.6 kAF), Karnes (3.9 kAF), Dimmit (3.7 kAF), and La Salle (2.9 kAF) counties. Although overall water use has increased, water use per well has decreased due to operational changes, including a shift from gas to oil and condensate production and the use of gelled HF treatments instead of slick-water treatments. Currently, operators recycle minimal amounts of flowback/produced water, with brackish water accounting for approximately 20% of total water use. Recycling remains limited due to insufficient flowback volumes for subsequent HF operations, particularly in the early stages. Flowback/produced water is primarily disposed of in injection wells, with approximately 2,500 Class II injection wells active between 2008 and 2012, many of which are associated with waterflood operations rather than disposal. Preferred disposal horizons include formations of the Navarro-Taylor Groups in the Maverick Basin and the Wilcox and Edwards formations.Bureau of Economic Geolog

Oil & Gas Water Use in Texas: Update to the 2011 Mining Water Use Report

In Spring 2012, we undertook an update of the hydraulic fracturing sections of the TWDB-sponsored report titled “Current and Projected Water Use in the Texas Mining and Oil and Gas Industry” that we published in June 2011 (Nicot et al., 2011). The 2011 report provided estimated county-level water use in the oil and gas industry in 2008 and projections to 2060. This 2012 update was prompted by two main events: (1) a major shift of the oil and gas industry from gas to oil production, displacing production centers across the state and impacting county-level amounts; (2) rapid development of technological advances, resulting in more common reuse and in the ability to use more brackish water. The timely update was enabled by a faster than anticipated development, translating into abundant statistical data sets from which to derive projections, and by an increased willingness of the industry to participate in providing detailed information about water use in its operations. This document follows the same methodology as the 2011 report but differs from it in two ways. Our current update clearly distinguishes between water use and water consumption. The 2011 report does not include reuse from neighboring hydraulic fracturing jobs, recycling from other industry operations or other treatment plants, and use of brackish water. Our update also presents three scenarios: high, low, and most likely water use and consumption with a focus on water consumption. This update has been reviewed by the TWDB and should supersede oil and gas industry projections from the 2011 report.Bureau of Economic Geolog

Numerical modeling of CO2 injection into a typical US Gulf Coast anticline structure

AbstractThis paper summarizes recent numerical modeling activities investigating geological CO2 sequestration project at the Cranfield field, Mississippi, USA, performed with the commercial compositional flow simulator CMG-GEM. The oilfield was produced from the 1940’s to the 1960’s but has been the recent recipient of an enhanced oil recovery (EOR) CO2 flood. The subset of actual site operations of interest to the BEG consists of (1) an early phase, object of this paper, in which CO2 is injected into the oil-bearing reservoir (the so-called Phase II) and (2) a second phase (started on December 1, 2009) in which CO2 is injected at a high rate (>100 kt/yr for several years) in the saline aquifer down dip of the reservoir (Phase III). We present the modeling efforts related to the early phase of injection (Phase II, started in July 2008) in which CO2 is injected into the oil-bearing reservoir. The objectives of the modeling effort are to (i) to gain insights on how to approach CO2 injection modeling at the site, (ii) to match recent pressure measurements at several wells including a dedicated observation well, and (iii) to vindicate the necessity of monitoring of reservoir pressure. Its intent is not necessarily to do a full-fledged history match of the historical production period (1940’s–1960’s).We conducted numerous repeat simulation runs to modify boundary conditions, fluid properties, and reservoir properties to match observed fluid responses to production and to injection. A good understanding of subsurface heterogeneities, and composition of the oil and gas components, and boundary conditions of the reservoir is the key to successful history matching. However, allocating the correct distribution of rock properties based on historical geophysical logs remained an area of uncertainty even as additional new data were obtained during characterization because of the complex interplay between depositional environment and strong overprint of diagenetic events. Parameters of utmost importance for a correct description of a flow field, in particular the relationship between porosity and permeability and the nature of permeability spatial variations remain uncertain as well as boundary conditions. The uncertainty was dealt with through sensitivity analyses. Ultimately, the constructed model shows a reasonable match with the data

Convection-diffusion-reaction of CO2-enriched brine in porous media: A pore-scale study

Bureau of Economic Geolog

Feasibility of Using Alternative Water Sources for Shale Gas Well Completions

The study presented in this document investigates alternative sources of water to be used in the last completion phase (commonly known as "fracing") of gas wells in the Barnett Shale play. It focuses on more rural counties (Montague, Jack, Palo Pinto, Parker, Erath, Hood, Somervell, Bosque, and Hill) located to the west of the core area (Denton, Johnson, Tarrant, and Wise Counties) where the Trinity aquifer is thin or absent. Millions of gallons are needed to perform the completion phase before gas wells are put online, and, in the past years, gas operators have mostly used: (1) groundwater from dedicated supply wells tapping the Trinity Aquifer, (2) surface water from large reservoirs and rivers, purchasing it from water-rights owners (private or state agencies such as river authorities), and, to a lesser extent, (3) surface water from private ponds and other water bodies, (4) treated water from municipalities and industrial users, and (5) water recycled from previous fracking operations. As gas production moves away from the core area toward the north, south, and west to access the remainder of the play, gas operators are faced with two challenges: (1) increased water scarcity and (2) measured reluctance to impact domestic and public water supplies.Bureau of Economic Geolog

Impact of CO2 Impurities on Storage Performance and Assurance Report on Tasks 1 and 2 Prepared for: CO2 Capture Project (Phase III) Revision 1

The goal of this study was to understand the impact of impurities (mostly N2, O2, and Ar, to which might be added CH4, commonly present to saturation levels in the subsurface) on CO2 plume dynamics, injectivity, and capacity. The study considered up to 15% volume for N2, 5% volume for O2, and 5% volume for Ar. Other gases such as CO, H2, and SOx, which could have non-negligible mole fractions, are not considered in the study. The problem is approached through an extended desktop study using the numerical modeling tool (multiphase flow code CMG-GEM). In order to work with accurate PVT data (Peng-Robinson EOS), laboratory experiments were performed early in the study to access viscosity and density of the mixtures. CMG-GEM relies on many empirical mixing rules for density and viscosity calculations that need to be calibrated and tuned. In parallel, a comprehensive literature survey was undertaken to collect information on solubility of those various mixture components into the aqueous phase under various subsurface pressure, temperature, and salinity conditions. The differential partitioning of gas components in the aqueous phase impacts the gas phase composition. The work presented in this document is part of a larger study that includes geochemical impact of impurities (reactivity of gas components with other components and with minerals), an aspect not treated here. Overall, geochemical processes could affect near-field properties such as injectivity and well integrity whereas larger-scale regional impacts can be studied through an understanding of plume dynamics. An important observation controlling all the results of the study is that viscosity and density of mixtures are lower than that of neat CO2 at identical temperature and pressure. Equally important to note, viscosity and density contrast between mixtures and neat CO2 decreases with depth. The numerical models used grow in complexity from simple box-like generic models, to which heterogeneity is added in a second step, to more realistic models constructed from two actual U.S. Gulf Coast Region locations (clastic sediments) and from a Canadian (Alberta) carbonate formation but representative of many sites around the world. The objective was to reproduce end-members of aquifer architecture such as (1) clean homogeneous, medium permeability sand; (2) homogeneous sand/clay, and (3) heterogeneous sand with discontinuous shale partings and continuous baffles. Progressively more complex systems, binary, ternary, and beyond, were investigated. The results are normalized with respect to corresponding neat CO2 case and draw on two key metrics, time to hit the top and maximum extent, are contrasted for 2 depths "shallow" (~5,000 ft, ~60ºC, 2500 psi, 100,000 mg/L) and "deep" (~10,000 ft, 125ºC, 4500 psi, 180,000 mg/L). Because O2, N2, and Ar have similar properties and behavior, they impact the CO2-dominated mixtures in a similar way, particularly at the concentration level of a couple percent molar and they can be merged in one unique component with properties of N2. However, the approximation deviates from the "true case" beyond a few percents.Bureau of Economic Geolog

Oidium neolycopersici: Intra-specific variability inferred from AFLP analysis and relationship with closely related powdery mildew fungi infecting various plant species

Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges