Evaluating Strategies for the Co-production of Water

The Challenge

Carbon Capture and Storage (CCS) operations involve the separation of carbon dioxide from its source (a step known as "capture") using liquid solvents (usually brine, which is water highly saturated with salt) and the pressurized injection of large amounts of this fluid into subsurface reservoirs. The challenges are to achieve optimal storage capacity for the captured carbon dioxide, and to provide careful management of over-pressures in the reservoirs to avoid unwanted geomechanical effects—all this while finding ways to reduce costs.

The Solution

To address these challenges, the brine pressurized in CCS operations and stored in reservoirs is used as the feedstock for an on-site desalination system for the co-production of water using nanofilteration and reverse osmosis (RO) water-treatment technologies. This solution provides a source of low-cost fresh water, which offsets operational costs and water needs.

This schematic shows a membrane-based water co-production plant using well-head pressure to desalinate brines recovered during underground CO₂ sequestration (click to enlarge image).

Pressurization of the brine feed is a major and very costly component in traditional desalination operations using seawater. By using the reservoir brine already at high pressure, this capital and operating component is eliminated.

To ensure these solutions are feasable, the Laboratory is currently conducting computer modeling (as well as laboratory-scale experimentation) to determine mineral scaling and osmotic pressure limitations for brines typical at CCS sites. Results to date (Aines et al., 2009) are very promising. Models have shown that using reservoir-pressured reverse osmosis to produce fresh water increases the storage capacity for the carbon dioxide. Results have also shown that effectively managing reservoir pressure appears to be possible at many proposed and potential sequestration sites.

The Expertise

The Laboratory has successfully demonstrated expertise in nanofilteration and reverse osmosis water treatment technologies and is capable of extending these technologies to novel applications. The Laboratory's computer software code EQ3/6 (Wolery, 1992) is being used to model brine thermodynamics while NNUFT (Nitao, 1998) code models complex reactive transport and reservoir pressure evolution. With analyzing and modeling expertise over a broad range of technical disciplines, the Laboratory has the resources needed to assess injection operations and to examine membrane treatment processes at a sufficiently detailed level to enable predictions of energy use, scaling potential, and optimization of CCS process configurations.

The Opportunity

Evaluating strategies for the co-production of water at proposed and potential CCS sites.

The Laboratory's extensive informatics capabilities care used to recommend particular water recovery system configurations for CCS sites and to provide the information needed to estimate the capital and operating costs of water recovery. The cost data is then fed into plans for implementing CCS operations.

Learn More

Fresh Water Generation from Aquifer-Pressured Carbon Storage: Interim Progress Report »
R. D. Aines, T. J. Wolery, Y. Hao, W. L. Bourcier. This document discribes geochemical modeling of high-salinity brines and covers the first six months of project execution (September 2008 to March 2009).

Reference Manual for the NUFT Flow and Transport Code »
J. J. Nitao. NUFT 3.0 is a suite of multi-phase, multicomponent computer models for numerical solution of non-isothermal flow and transport in porous media with application to subsurface contaminant-transport problems.

EQ3/6 Package Overview and Installation Guide »
J. J. Nitao. EQ3/6 (version 7.0) is a software package for geochemical modeling of aqueous systems.

Predicting the Consequences of Releases of CO₂

The Challenge

There are risks assosciated with carbon capture and storage (CCS) beyond the operational liability of capturing, transporting, and injecting carbon dioxide (CO₂). After CO₂ has been injected into an injection well, failure of the well has the potential of releasing huge amounts of CO₂ that can cause serious damage to the environment and human health. Managing these risks presents a unique set of challenges because of the large number of proposed and potential CCS sites, the long time periods over which the carbon is stored in subsurface geological formations, and the ever-changing characteristics of the geophysical systems.

As if those challenges weren't enough, an equally significant challenge involves predicting the consequences to the environment and human health if (or when) a release of CO₂ should occur at a CSS site.

The Solution

Analysis using energy informatics provides a means to meet the challege of predicting the consequences of a release of CO₂. First steps would be to collect and assess information about the topography, climatic conditions, and other site-dependent characteristics at each CCS site. Such data are critical to the development of computer models for predicting the consequences of CO₂ releases. Livermore Laboratory has a wealth of experience in collecting data and conducting assessments.

The Expertise

The National Atmospheric Release Advisory Center (NARAC) at Livermore Laboratory provides the tools and expert services to map the spread of airborne hazardous materials. These tools include global geographical and real-time meteorological databases to support model calculations. The tools also include modules that enable the modeling of flow and dispersion in settings where there are buildings and complex topography.

NARAC conducts research and development using novel tools and capabilities. This figure shows a computer-generated model of dense-gas dispersion in a complex setting involving interactions with terrain and buildings (click to enlarge image).

NARAC has provided contingency planning services to over 300 government organizations. They have predicted the dispersion of plumes from a wide variety of sources, such as spills of toxic industrial chemicals, smoke from fires and smoke-stack emissions. On average, NARAC responds to over 8,000 requests each year, which includes requests for technical and scientific staff to participate in 100 major exercises and 25 incidents and assessments related to atmospheric releases.

The Opportunity

Predicting the consequences of atmospheric releases of CO₂.

In advance of an incident, Livermore Laboratory uses NARAC's expertise to simulate CO₂ levels from actual terrain, weather and historical climate data obtained at the CSS site.

Predicting the potential hazards using computer models helps CCS site operators develop effective emergency response plans, communication strategies and public outreach programs to appropriately respond to incidents. In addition, the computer models of airborne toxic releases enable event reconstruction.

Learn More

National Atmospheric Release Advisory Center »
This Livermore Laboratory organization provides tools and services to the U.S. Federal Government that map the probable spread of hazardous material released into the atmosphere.

Climate Change »
U.S. Environmental Protection Agency Web site that openly describes what's known, what's very likely, and what's not certain about the effects of climate change.

U.S. Global Change Research Program »
The U.S. Global Change Research Program coordinates and integrates U.S. Federal Government research on changes in the global environment and the implications for society.

Simulating Subsurface Pressure Build-up

The Challenge

One challenge facing the successful implementation of carbon capture and storage (CCS) is relieving the pressure build-up caused by large-volume, sustained carbon dioxide (CO₂) injected into subsurface geological formations. The pressure wave creates stress gradients. Stress gradients can trigger dilation or closure of faults or planar rock fractures. They can also lead to slippage and dislocation along faults and fractures, trigger changes in the hydraulic connectivity within the injection reservoir, and induce microseismic events.

The Solution

To address this challenge, Livermore Laboratory use their computer codes NUFT, LDEC, FRAC-HMC and WPP to simulate key processes, predict specific outcomes and events, and assess field-monitoring data to possibly discover ways to relieve subsurface pressure build up.

NUFT is based on a non-isothermal/thermal, unsaturated/saturated, flow and transport model (Nitao, 1998) with an associated geochemical database. It is used to simulate coupled fluid movement and chemical reactions in geologic media.

LDEC was developed to simulate the deformation of extensively fractured rock masses and is used to predict permeability evolution in fractured and faulted sequestration targets (Morris et al., 2006; Morris et al., 2009).

FRAC-HMC is a discrete-fracture-network flow computer code that accommodates stress-induced changes in transmissivity at the pore-scale (Detwiler and Rajaram, 2006).

WPP is a comupter program for simulating wave propagation with substantial capabilities for three-dimensional seismic modeling.

The Expertise

Currently, Livermore Laboratory's world-class experts are involved in several large CO₂ injection projects. Most notable among these projects are CCS sites located at In Salah, Algeria, and Weyburn, Canada. Also, Livermore Laboratory is one of the lead institutions in U. S. Department of Energy's (DOE's) National Risk Assessment Program tasked to predict the integrity of the caprock seals that trap the CO₂ in injection wells.

This LDEC model dipicts fracture networks and faults in the Krechba Field at the In Salah, Algeria, carbon sequestration and storage site. It predicts extensive permeability enhancement about the injector due to hydromechanical modification of the fracture network. (click to enlarge image).

The Opportunity

Simulating subsurface pressure build-up in CO₂ injection wells.

Geomechanical modeling of fault-failure envelopes: Given the geometry of major faults and fractures that may be present in and above the reservoir and estimates of the in-situ stresses and mechanical properties, the minimum change in effective stress needed to induce slip along portions of the fault can be forecasted. By incrementally increasing pore pressures within regions of the reservoir in the model, estimates of failure pressures along fault elements within the reservoir can be developed. This analysis can provide estimates of the magnitude of reservoir pressure perturbations likely to cause slip along major faults.

Simulation of induced microseismicity: The orientation and magnitude of local stresses and fracture orientations provide the initial conditions for modeling seismic events. Shear failures, induced by changing pore pressures, produce seismic events that provide source terms for predicting seismograms through wave propagation from the reservoir to the surface. Modeling the failure events as seismic source terms also provides a tool for inverting microseismic results to better interpret the relation between monitored events, CO₂ and pressure distribution at depth.

Learn More

Predicting dissolution patterns in variable aperture fractures: Evaluation of an enhanced depth-averaged computational model »
R.L Detwiler and H. Rajaram. Water Resources Research. 43, W04403, doi:10.1029/2006WR005147, 4 April 2007

Simulations of fracture and fragmentation of geologic materials using combined FEM/DEM analysis »
J. P. Morris. International Journal of Impact Engineering. 33, 463–473, (2006)

Eighth Annual Conference on Carbon Capture and Sequestration »
J. P. Morris. Pittsburgh, PA, U.S.A. (2009).

Reference Manual for the NUFT Flow and Transport Code »
NUFT 3.0 is a suite of multi-phase, multicomponent computer models for numerical solution of non-isothermal flow and transport in porous media with application to subsurface contaminant-transport problems.

Modeling Reactive Transport of CO₂ in Groundwater

The Challenge

Protecting groundwater resources is one of the most vital requirements for developing large-scale carbon dioxide (CO₂) subsurface, geological storage. Initially, large-scale injections displaced water from saline formations at depth, which, in turn, displaced significant water volumes in shallow aquifers. Another concern is the possible release of small amounts of CO₂, which have the potential to affect water quality because CO₂ reacts with brines and enhances dissolution and desorption of trace elements from aquifer host rock. These adverse geochemical transformations may cause groundwater quality to exceed the maximum contaminant levels mandated by the U. S. Environmental Protection Agency as part of their national drinking water standards (Carroll et al., 2009, Carroll 2009).

A three-dimensional geologic model based on a central High Plains aquifer sand and clay lithology.

The Expertise

This challenge is no problem for Livermore Laboratory. The Laboratory has over 25 years of practical experience in protecting and remediating groundwater resources with expertise in the complex reactive transport modeling needed to assess potential groundwater contamination from CO₂ storage operations. Experience includes tackling a variety of problems, including assessments of geological high-level nuclear waste repositories, oil and gas reservoirs, groundwater remediation, and subsurface sequestration of CO₂. Livermore Laboratory's NUFT computer code (non-isothermal/thermal, unsaturated/saturated, flow and transport) is a powerful collection of databases and software (Nitao, 1998). NUFT simulates the flow of multiple liquids and gases and chemical reactions in geologic media. Livermore Laboratory's capabilities in this area include simulation studies and the design and implementation of groundwater-monitoring-well networks.

The Opportunity

Modeling reactive transport of CO₂ in groundwater.

Using Livermore Laboratory's suite of sophisticed computer modeling tools, the potential effects on the chemical composition of aquifers near CCS sites can be simulated. These models provide researchers with the information they need to identify monitoring and verification needs to ensure groundwater is protected.

Learn More

Trace metal release from Frio sandstone reacted with CO₂ and 1.5 N NaCl Brine at 60 Degrees C »
S. Carroll. Eighth Annual Conference on Carbon Capture and Sequestration. Pittsburgh, PA, U.S.A. (2009).

Geochemical detection of carbon dioxide in dilute aquifers »
S. Carroll, Y. Hao, and R. Aines. This document focuses on using static equilibrium and reactive transport computer simulations to test the hypotheses that perturbations in water chemistry associated with a CO₂ leak into dilute groundwater are important measures for the potential release of CO₂ into the atmosphere.

Reference Manual for the NUFT Flow and Transport Code »
J. J. Nitao. NUFT 3.0 is a suite of multi-phase, multicomponent computer models for numerical solution of non-isothermal flow and transport in porous media with application to subsurface contaminant-transport problems.

Monitoring CO₂ Plumes in Subsurface

The Challenge

To demonstrate to regulartory boards, site operators and the community that a carbon sequestration site is safe, it is essential to monitor carbon dioxide (CO₂) plume characteristics in the injection reservoirs located deep beneath the earth's surface.

Monitoring plume characteristics requires sophisticated sensors, data acquisition devices and imaging instruments that are capable of obtaining accurate measurements from boreholes. The results of the monitoring are analyzed to ensure that the site is operating as expected and that accreditation is warranted. Even with the proper equipment, plume movement can be difficult to reconstruct due to uncertainties in reservoir structure and unknown multiphase processes.

The Solution

Two computer software modules of particular interest for analyzing CO₂ plumes in subsurface reservoirs are electrical resistance tomography (ERT) and interometric systhetic aperture radar (InSAR).

ERT is used to convert a large number of resistance measurements into an image of electrical resistivity distribution. This is possible because changes in CO₂ concentration and saturation cause changes in resistivity, making ERT a useful monitoring tool (Carrigan et al., 2009). ERT monitoring is capable of signaling potential surface deformation because observable changes in fluid pressure and volume within a deep reservoir often result in measurable surface deformation.

InSAR data is used to compare predited uplift at the In Salah sequestration site in central Algeria at one year.

InSAR is used to map surface deformation at high resolution over large areas using radar images from satellites. The deformation maps are then analyzed to determine the migration of subsurface fluids.

Livermore Laboratory has also developed novel platforms to formally integrate and compare multiple monitoring data sets. The information obtained from these tools is used to plan effective and efficient monitoring programs for injection sites. One such tool is the Stochastic Engine (SE).

SE processes data using Bayesian inference, which is a probabilistic approach that combines observed data, geophysical forward models, and prior knowledge (such as existing structural geology maps) to identify permeable layers and fracture zones (Ramirez et al., 2006). The results are sample models of the likely plumes that are consistent with the data collected. The SE approach, though computationally intensive, leads to interpretation of monitoring results that is more accurate and less costly than conventional approaches.

The Expertise

For many decades, Livermore Laboratory has played a central role in developing geophysical approaches to characaterize subsurface features.

Livermore Laboratory has used ERT to monitor environmental remediation projects using steam injection and taken baseline data at a field test location in Mississippi as part of the Southeast Regional Carbon Sequestration Partnership's (SECARB) Gulf Coast Stacked Storage Project.

The Laboratory is currently using deformation maps derived from InSAR to constrain flow simulations of the CO₂ plume activity at the In Salah sequestration site in central Algeria.

The Opportunity

Monitoring CO₂ plumes in subsurface.

The Laboratory's expertise can use InSAR, ERT, and SE to design a data collection system network and then oversee its installation, collect and analyze baseline data, combine simulation studies and estimates of ground deformation data and monitor CCS site operations. This data collection system network helps process, invert, interpret, and quantify the probability of CO₂ plume characteristics and distribution at CCS sites.

Learn More

Eighth Annual Conference on Carbon Capture and Sequestration »
C. Carrigan. Pittsburgh, PA, U.S.A. (2009).

Eighth Int. Conf. on Greenhouse Gas Control Technologies »
A. Ramirez. (2006).

Characterizing and Assessing Subsurface Geology

The Challenge

The reliability, safety, and security of a carbon capture and storage (CCS) site depend on accurate characterization and assessment of the site's physical and geological conditions. Effective characterization and assessment of a CCS site requires experience in obtaining field-data, knowledge of subsurface geology, an understanding of the ever-changing geophysical systems, and enough computer power to generate realistic simulations and geomodels.

The Solution

One key solution to solving this challenge is the construction of site-specific, coumputer-generated geomodels. The geomodels would be populated with site-relevant data obtained from partners and information in the public domain. Efforts would begin by focusing on the physical and geological characterization of the reservoir-caprock-overburden system, including hydrologic data; structural and textural data such as faults, joints, and fractures; stratigraphic data; mechanical information (e.g., stress azimuth, breakouts); and geochemical and compositional information.

Computer-generated geologic model of part of the southern San Joaquin Basin, Calif., U.S.A. (click to enlarge image).

The Expertise

Livermore Laboratory has extensive experience in developing three-dimensional static geologic models using EarthVision, a commercial computer platform that integrates well data, geophysical measurements, and surface geologic mappings.

For example, the Laboratory recently constructed a regional three-dimensional geologic model of the southern San Joaquin basin in California for the Westcarb Kimberlina CO₂ sequestration demonstration project (Wagoner, 2009). This model included the entire tertiary stratigraphic section from the surface to the pre-tertiary basement complex, and over 140 faults. In addition, Livermore Laboratory used these geologic models as a framework for the complex reactive transport and geomechanics modeling necessary to assess likely long-term CCS site performance and optimal operating conditions.

The Opportunity

Characterizing and assessing subsurface geology.

It is necessary to integrate data on the geophysical characteristics of the site, including velocity models, acoustic properties, and distribution of hydrocarbons within the reservoir, and to work closely with project teams, service companies, and operators to format, visualize, interpret, share, and update the geomodels.

Site characterization and assessment processes are used to identify geological features and hazards. Geological, geophysical and hydrological teams help to estimate key site parameters and conditions (e.g., capacity), likely plume extend and key hazards (e.g., wells and faults). Also, the geomodels of the injection site are used in carbon capture and storage studies. These efforts assist in stratigraphic characterization of key units (e.g., seals) and provide additional site project support.