Joonsang Park

Using Prokaryotes for Carbon Capture Storage

Geological storage of CO2 is a fast-developing technology that can mitigate rising carbon emissions. However, there are environmental concerns with the long-term storage and implications of a leak from a carbon capture storage (CCS) site. Traditional monitoring lacks clear protocols and relies heavily on physical methods. Here, we discuss the potential of biotechnology, focusing on microbes with a natural ability to utilize and assimilate CO2 through different metabolic pathways. We propose the use of natural microbial communities for CCS monitoring and CO2 utilization, and, with examples, demonstrate how synthetic biology may maximize CO2 uptake within and above storage sites. An integrated physical and biological approach, combined with metagenomics data and biotechnological advances, will enhance CO2 sequestration and prevent large-scale leakages.

Response of Layered Half-Space Obtained Directly in the Time Domain, Part II: SV-P and Three-Dimensional Sources

In Part I of this set of two companion articles we presented a new, rigorous method to obtain the seismic response of horizontally layered, viscoelastic (or elastic) half-spaces caused by antiplane ( SH ) sources anywhere. This method is formulated directly in the time domain, and can be applied even in the absence of attenuation. This article (Part II) generalizes the concept to SV-P line sources and to three-dimensional point sources, including seismic moments.

Response of Layered Half-Space Obtained Directly in the Time Domain, Part I: SH Sources

A rigorous method is presented to obtain—directly in the time domain and without the need for an integral transform over frequencies—the seismic response of horizontally layered, viscoelastic half-spaces due to arbitrarily distributed (or concentrated) sources. The method is based on exact expressions for the response of the underlying half-space cast in the wavenumber-time domain, and a complete modal solution in that domain for the layers. The proposed method is highly effective and avoids the problems of the usual propagator matrix method that arise when numerical integrations over both frequencies and wavenumbers are carried out, especially the waviness of the kernels due to resonances and reverberations in the layers when damping is light or even absent. Part I presents the basic methodology for the relatively simple case of antiplane SH sources in two-dimensional space, while Part II generalizes the concept to two-dimensional SV - P line sources and to three- dimensional point sources, including seismic couples.

Vertically integrated models for coupled two‐phase flow and geomechanics in porous media

Models of reduced dimensionality have been found to be particularly attractive in simulating the fate of injected CO2 in supercritical state in the context of carbon capture and storage. This is motivated by the confluence of three aspects: the strong buoyant segregation of the lighter CO2 phase above water, the relatively long time scales associated with storage, and finally the large aspect ratios that characterize the geometry of typical storage aquifers. However, to date, these models have been confined to considering only the flow problem, as the coupling between reduced dimensionality models for flow and models for geomechanical response has previously not been developed. Herein, we develop a fully coupled, reduced dimension, model for multiphase flow and geomechanics. It is characterized by the aquifer(s) being of lower dimension(s), while the surrounding overburden and underburden being of full dimension. The model allows for general constitutive functions for fluid flow (relative permeability and capillary pressure) and uses the standard Biot coupling between the flow and mechanical equations. The coupled model retains all the simplicities of reduced-dimensional models for flow, including less stiff nonlinear systems of equations (since the upscaled constitutive functions are closer to linear), longer time steps (since the high grid resolution in the vertical direction can be avoided), and less degrees of freedom. We illustrate the applicability of the new coupled model through both a validation study and a practical computational example.

Geophysical Monitoring of CO2 Flow During Sandstone Flooding Experiments

In this study, liquid CO2 is injected into fully brine saturated reservoir core samples in the laboratory, and consequently changes in electrical resistivity, acoustic velocities (ultrasonic frequency) and their anisotropy are measured. To enhance the spatial resolution, a system enabling velocity and resistivity measurements at different points and in different directions along the specimens axial direction has been developed. Electrical resistivity and acoustic velocity and amplitude are all clearly influenced by pore-scale heterogeneity and fluid flow pattern and it is important to study this interaction. So far, focus has been related to CO2 geological storage, but the outline of the study is believed to also be applicable for CO2 injection for enhanced oil recovery (EOR). The study is still ongoing and some preliminary results are presented here and discussed.

Fast Evaluation of Fluid-rock Coupling in CO2 Storage

Modelling plays an important role in providing capacity estimates and analysing injectivity, long-term safety and risk factors for future storage sites. Hundreds and thousands of potential sites will have to be screened for suitability before more detailed studies are done. In this context, fast yet reliable methods will have to be developed involving simplified models but without losing too much of the accuracy. One key parameter for choosing a storage site is the injectivity; how fast can the CO2 be injected. The basics of hydro-mechanical modelling is explained and a conceptual model for single-phase fluid flow is defined. Various levels of complexity of the governing equations are derived, by considering standard methods and using constant and non-linear hydro-mechanical properties these models are compared. Results show that well defined input data makes the coupling to the geomechanical processes redundant, resulting in considerable savings in computational effort to get reliable and accurate estimates of injection pressure.

Multi-modal Surface Waves for Site Characterization - Results from a Unique Marine Shear Wave Experiment

We revisit a unique marine seismic data set collected with a densely populated ocean bottom cable (2.5 m effective channel spacing) and a prototype shear wave vibrator at the Gjoa field, offshore Norway. Whereas the survey was primarly designed for reservoir illumination, multi-modal surface waves stand out on the seismic data (both time-offset and frequency-wavenumber domains), in the frequency band between 3 and 35 Hz. As the source was operated in both in-line and cross-line direction, we identify multiple Scholte and Love waves that were subsequently used for a constrained inversion for obtaining a detailed shear wave velocity with depth, down to 50 m. In addition, a comparison of the velocities yields an estimate on shear wave anisotropy in the shallow sub-surface, with up to 15%. The data are further used to determine attenuation, a second critical parameter affecting wave propagation and dynamic response of seabed-founded structures, which can also be important for soil characterization. Tuned forward modelling of the fundamental surface wave mode yields shear wave damping of less than 1% for the deepwater soft soils. The attenuation coefficient increases linearly with frequency, and indicates that the damping is to a large degree viscous rather than due to hysteresis.

Resistivity and Ultrasonic Velocity Measurements During CO2-brine Drainage and Imbibition

Two different experimental approaches for studying CO2–brine displacement and relation to a heterogeneous (layered) rock drilled perpendicular and parallel to bedding under isotropic is presented: One uses CT imaging to locally resolve the structural heterogeneity effect on pore fluid distribution and saturation and directly linking it to the geophysical measurements (resistivity and sonic velocity), the other using a ring electrode sample sleeve design to resolve local changes in resistivity in the flow direction during displacement. The studies demonstrates the importance and impact of sub core scale heterogeneity and flow/permeability anisotropy in dictating the electrical conductivity and sonic velocity response, locally and globally, during drainage and imbibition.

Numerical dispersion of SH waves in the thin-layer method

Publisher Summary This chapter presents numerical dispersion of SH waves in the thin-layer method (TLM). The TLM is an effective numerical tool for the analysis of stresses, deformations, and wave motions in laminated media. In a nutshell, the TLM combines the finite element method in the direction of layering together with analytical solutions in the remaining directions. Because of the partial discretization employed, the TLM is subjected to numerical dispersion, the degree of which depends on the refinement of the model. The chapter characterizes analytically the numerical dispersion in the TLM for both linear and quadratic expansions in the context of antiplane waves. It develops optimal tuning factors to minimize the numerical dispersion error and improve the accuracy. The numerical results obtained are compared with both the TLM and the exact continuous models to verify the effectiveness of optimal tuning factors.