Arthur W. Wells

Probabilistic Design of a Near-Surface CO2 Leak Detection System

A methodology is developed for predicting the performance of near-surface CO(2) leak detection systems at geologic sequestration sites. The methodology integrates site characterization and modeling to predict the statistical properties of natural CO(2) fluxes, the transport of CO(2) from potential subsurface leakage points, and the detection of CO(2) surface fluxes by the monitoring network. The probability of leak detection is computed as the probability that the leakage signal is sufficient to increase the total flux beyond a statistically determined threshold. The methodology is illustrated for a highly idealized site monitored with CO(2) accumulation chamber measurements taken on a uniform grid. The TOUGH2 code is used to predict the spatial profile of surface CO(2) fluxes resulting from different leakage rates and different soil permeabilities. A response surface is fit to the TOUGH2 results to allow interpolation across a continuous range of values of permeability and leakage rate. The spatial distribution of leakage probability is assumed uniform in this application. Nonlinear, nonmonotonic relationships of network performance to soil permeability and network density are evident. In general, dense networks (with ∼10-20 m between monitors) are required to ensure a moderate to high probability of leak detection.

Monitoring, mitigation, and verification at sequestration sites: SEQURE technologies and the challenge for geophysical detection

Editors note: SEQURE is a trademark of The National Energy Technology Laboratory. A critical component of the National Energy Technology Laboratorys Sequestration Program is the development of tools that can reliably monitor and quantify the amount of CO2 that leaks to the surface. One major requirement for the commercial application of geologic sequestration is accurate leak detection; i.e., leak monitoring and accurate estimation of leak volumes through continued monitoring. This is essential to assure that long-term sequestration is achieved. Significant leakage from the sequestration reservoir defeats the purpose of sequestration, which is to stabilize and then reduce atmospheric concentrations of CO2 for several hundreds to thousands of years. Multiple investigators have attempted to estimate the amount of leakage that is acceptable (e.g., Pacala, 2002; Hepple and Benson, 2002; Dooley and Wise, 2002; Herzog, 2002). Their estimates vary considerably, and range from 1% to 0.01% per annum which leads to leakage of 50% of the injected CO2 volume in 70 to 7000 years, respectively.

Ground-penetrating radar survey and tracer observations at the West Pearl Queen carbon sequestration pilot site, New Mexico

The potential for leakage of injected CO2 at carbon sequestration sites is a significant concern in the design and deployment of long-term carbon sequestration efforts. Effective and reliable monitoring of near-surface environments in the vicinity of these sites is essential to ensure the viability of sequestration activities as well as long-term public and environmental safety. Identification of geologic features (such as faults, fracture zones, and solution enhanced joints that might facilitate release of injected CO2 back into the atmosphere) is a key step in this process. This study reports on near-surface geologic and geophysical characterization efforts conducted at the Department of Energy National Energy Technology Laboratory (NETL) West Pearl Queen carbon sequestration pilot site in southeastern New Mexico, USA, and their use for uncovering possible mechanisms associated with escape of small amounts of perfluorocarbon tracers injected with the CO2.

Preconversion chemistry and liquefaction of coal in the presence of a molybdenum-containing catalyst

Publisher Summary This chapter discusses the interactions of a catalyst and several different solvent media with a bituminous coal at various temperatures. Information on the influence of the catalyst during the early stages of conversion is also presented. The results presented show the importance of a solvent medium in enhancing the primary dissolution of coal at lower reaction temperatures. With a catalyst, the presence of coal-derived products provided the best results under these conditions. Softening and solubilization of the coal are likely the important factors in this regime. Analysis of short time products obtained at 375°C show that a major role of the catalyst in the beginning phases of coal dissolution is to facilitate the transfer of hydrogen to aromatic species in the coal. Catalyst is effective above 375°C when used alone.