Earth Sciences Division (ESD) Department of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL)

ZERT Task 4:  Fundamental geochemical and hydrological investigations of long-term CO2 storage

Task 4 Leadership ZERT logo

Task Lead (primary contact)

Tim Kneafsey

Key Personnel/Participants

Dmitriy Silin, Tetsu Tokunaga, Jiamin Wan, Jong-Won Jung

ZERT Task 4 Goal

To develop understanding and confidence in solubility trapping, residual gas trapping and mineral trapping, and to identify new trapping mechanisms that can contribute to even greater storage security.

ZERT Task 4 Overview

Theory and experiments will be used to develop a greater understanding of solubility trapping, residual gas trapping and mineral trapping and to identify new trapping mechanisms that can provide even greater storage security.

     Experiments to improve our understanding of residual gas trapping will be conducted in a high pressure 1-D column with X-Ray CT scanning capability.  These experiments are designed to allow monitoring the evolution of trapped gas over time and as fluid slowly dissolves the trapped gas.  Theoretical studies and numerical simulation will be used to interpret and generalize the results from these experiments.  Planning to include measurements to correlate gas-water saturation with geophysical properties (e.g., acoustic wave speed, electrical conductivity) will be undertaken for future investigation in this task.

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Frio sandstone cross-section CO<sub>2</sub> pore space distribution Iliary pressure curves for Frio sandstone.
A cross-section of Frio sandstone partially saturated with water (52%) and CO2 (48%). The black fillings show CO2 and the blue color marks water. Image size is presented by the number of voxels CO2 distribution in the pore space at 34% (left) and 75% (right) gas saturation. Capillary pressure curves for Frio sandstone. Red curves are computed capillary pressures for different parts of the whole image. The blue curve is mercury injection data. The collapse of red curves indicates that the sample size selected for analysis is representative enough. Computed underestimate water saturation at high capillary pressures due to the presence of microporosity (left). The data fitting problem is fixed by introducing a microporosity correction factor (right).
ZERT Task 4 Subtasks

Subtask 4.1. Core flow-through and scanning:

Theory and laboratory experiments are used to develop a greater understanding of solubility trapping, residual gas trapping, and mineral trapping to identify new trapping mechanisms that can provide even greater storage security over long time scales.  Experiments to improve our understanding of residual gas trapping are conducted in a high-pressure 1-D column with X-Ray CT scanning capability.  These experiments will monitor the evolution of trapped gas over time and as fluid slowly dissolves the trapped gas.  Theoretical studies and numerical simulation will be used to interpret and generalize the results from these experiments.

Subtask 4.2. Interfacial tension studies:

Interfacial tension of scCO2 relative to water is the key property controlling residual gas trapping.  We are planning investigations to measure and model the effects of co-injected gases (e.g., N2, Ar, H2S, SOx, etc.) on interfacial tension for CO2 mixtures including effects of mixed wettability.  One approach we are using is the pendulum drop approach.  In addition, we are using a capillary pressure cell to measure interfacial tension.

Subtask 4.3. Evolution of rock flow properties by mineral trapping:

Mineral trapping is a promising mechanism of geologic storage of CO2.  Mineral trapping modifies the pore space geometry that affects the flow properties of the rock.  The evolution of the relative permeabilities and the capillary pressure will affect both the flow near the wellbore, and the long-term trapping of gas.  Experiments are difficult and time consuming.  Modeling can provide useful insights by simulating various what-if scenarios.  We are using the Maximal Inscribed Spheres method to simulate the flow in the changing pore-space geometry and quantify the impact of mineralization on the two-phase flow properties of the rock.  The simulations rely on the micro-CT images of rock samples obtained earlier within this task.  Micro-CT studies of rock mineralization will be used for calibration and verification of the models.  Results of this effort can be used as input data in the TOUGH2 simulations mentioned in Task 2.