Submarine storage in near-shore volcanic regions is attractive because the extensive reservoir volumes may be accessed with on-shore drilling and injection, the formation waters are cold so CO2 is relatively dense, and CO2-hydrate may be an additional trapping mechanism. This project aims to critically evaluate this new storage paradigm focusing initially on two regions: Hawaii and Japan. The ultimate goal is to develop a reservoir model to assess the viability of large-scale CO2 storage in known and generic saline volcanic basins. The components of the proposed research are (*recently added efforts) (info last updated Dec 2021):
- Evaluation, and hydrologic and geochemical characterization of potential storage reservoirs in the Hawaiian Islands, Northwestern U.S., and the Japanese Islands. (In year 2 this task will be expanded to include regions of Iceland far from geothermal areas.)
- Chemical and isotopic analysis of available subsurface fluid samples to place constraints on the age, source, flow rates, and mineral reactivity of fluids.
- *Analysis of available borehole water level and temperature data to constrain the formation permeability and fluid flow at storage depths.
- Laboratory experiments aimed at understanding the contributions of mineralization and capillary effects to CO2
- *Hydrologic modeling of coastal basins to understand controls on thermohaline circulation and subsurface temperatures.
- *Development of quantitative models to assess the efficacy of CO2 hydrate formation as a subsurface trapping mechanism.
- Process models and dimensional analysis to understand the relative timescales of the competing processes of injection flow, background flow, buoyancy-driven flow, structural trapping, capillary trapping, dissolution trapping, mineral trapping and hydrate trapping.
Basin scale flow and reactive transport modeling of CO2 injection in generic saline basalt formations and at sites modeled after those identified in Hawaii and Japan.
Task: Hydrologic and geochemical characterization of potential storage reservoirs
Executive Summary: Evaluation, and hydrologic and geochemical characterization of potential storage reservoirs in the Hawaiian Islands, Northwestern U.S., the Japanese Islands, and Iceland.
Background: The ultimate objective of this project is to identify the parameter ranges required for optimal injection and trapping in basaltic rocks and then map these onto known or measured values for the Hawaiian island chain, Japan, Iceland, and eventually other areas where we can find suitable information.
Due to the paucity of hydrologic characterization of deep volcanic basins, we are setting up the capability to model 2D thermohaline circulation of the seawater through volcanic edifices that we hope will help us understand how formation permeability relates to subsurface temperature and flow velocities.
Task: Chemical and isotopic analysis of subsurface fluid samples
Executive Summary: Aqueous fluids saturated with CO2 are reactive with basaltic rocks, so there is the prospect of a substantial fraction of injected CO2 being converted to carbonate minerals within decades to centuries (Zhang and DePaolo, 2017; also see DePaolo et al., 2021). CO2 is also soluble in water, and flow through the volcanic rocks could enhance solubility trapping. Research questions involving geochemistry include:
- Are chemical reactions between basalt and carbonated fluid fast enough at low temperature to expect significant CO2 mineralization?
- Can slow circulation of seawater or brackish water through heterogeneous pore space accelerate CO2 dissolution?
- What is the relationship between the residence time of fluids in the volcanic pile and the timescale for mineralization, capillary, or solubility trapping?
- Can fluid residence times be estimated based on Sr isotope and radiocarbon measurements of fluids sampled in the HSDP2 well.
Background: An important characteristic of the NE flank of the island of Hawaii, and we suspect of many other near-shore marine volcanic regions, is low subsurface temperatures. The depressed temperature is a result of cold deep seawater circulating through the flanks of the volcanic pile at depths down to 3 to 5 kilometers and at rates that are sufficiently fast to cool the rocks to temperatures well below a normal conductive geotherm (Thomas et al., 1996; Büttner and Huenges, 2003). Measurements of fluid samples from 2000 to 3000 meters depth indicate substantial reaction with the basalts.
Task: Process models and dimensional analysis
Executive Summary: Process models and dimensional analysis to understand the relative timescales of the competing processes of injection flow, background flow, buoyancy-driven flow, structural trapping, capillary trapping, dissolution trapping, mineral trapping and hydrate trapping.
Background: Simulation studies are aimed at determining the relative magnitudes of the contributions to transport and trapping of the various mechanisms as well as the time scales over which they function most effectively to immobilize or release CO2.
Task: Laboratory experiments
Executive Summary: Laboratory experiments aimed at understanding the contributions of geochemistry and capillary effects to CO2 trapping.
Background: Our initial objective was to evaluate the roles of secondary mineral reactions in mineral trapping of CO2. This is still an interesting issue, but perhaps a more fundamental one is to get the reaction kinetics better constrained for the major mineralogical components of basalt – plagioclase feldspar, clinopyroxene, and glass. Literature values for plagioclase (PLAG) and clinopyroxene (CPX) vary by factors of 100 to 1000 at low temperature, and few studies have been done using CO2-saturated water or seawater (Beckingham et al., 2016; 2017) in a way that allows retrieval of the reaction rate constants from the experimental data. Hence our focus for this task is experiments designed to do just that. These experiments are being carried out at RITE by Saeko Mito, using techniques reported on previously (Mito et al., 2008). Don DePaolo and Nick Pester from LBNL are involved in experiment design and interpretation. John Christensen will be involved for isotopic analysis of fluid samples, which will start in a month or two.
Task: Reactive transport models
Executive Summary: Basin scale reactive transport simulations to integrate available knowledge and information to evaluate the likely evolution of CO2 injected into the subsurface in saline volcanic basins and the efficiency of overall trapping.
Background: To evaluate the efficacy of CO2 disposal in deep saline volcanic basins requires 2D and 3D reactive transport simulations. Such simulations can help to evaluate the relative roles and timescales of all trapping mechanisms, and the effects of subsurface fluid convection and hydrate formation. The target is to evaluate all but hydrate formation first, and then to add hydrate formation separately. This approach is planned mainly because there is not currently software that will do hydrates as well as everything else.
With additional contributions from: