Download Controlled release test facility to develop environmental monitoring

Controlled release test facility to develop environmental monitoring techniques for
geologically stored CO2 in Korea
Seong-Chun Jun1 Jeong-Yong Cheon1 Jong-Hwa Yi1 Seong-Taek Yun2
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GeoGreen21 Co. Ltd.
Department of Earth and Environmental Sciences, Korea University
Abstract
Geologic storage of CO2 is considered as a promising technology to significantly mitigate CO2
emission into the atmosphere. However an unexpected leakage of stored CO2 could occur, various
geophysical and geochemical monitoring techniques have been proposed to secure geologic CO2
storage. Also proper monitoring techniques should be applied for a storage site based on the sitespecific geologic condition. In 2014 the Korea CO2 Storage Environmental Management (KCOSEM) Research Center has been inaugurated by the support from Ministry of Environment to
perform multidisciplinary researches on environmental risk management of geologic carbon storage.
K-COSEM had planned two field sets of controlled CO2 release tests in unsaturated and saturated
zones to develop efficient monitoring tools for leaked CO2 through soil/groundwater and to assess
the impacts of CO2 leakage on subsurface ecosystems. The test facility was named EIT
(Environment Impact Evaluation Test Facility on Seepage of Geologically Stored CO2). From 2014
to 2015, site selection and characterization, installation and preliminary operation of unsaturated
zone EIT, and saturated zone EIT installation were performed.
The experimental site is located in Eumseong-gun (Chungcheongbuk-do) about 80 km southeast of
Seoul. The site is a low hilly area, and geology is Jurassic biotite granite and Quatenary alluvium.
The drill log of site shows very thin alluvium and thick weathered zone about 60~65m. Ground
water table is located at 14~15 m depth, and groundwater flows from northwest to southeast with
hydraulic gradients of about 0.003~0.005. Experimental target layer is weathered zone (soil, mainly
sand), and hydraulic conductivity of that layer is about 10-4~10-3 cm/sec. The major minerals of
weathered zone are quartz, albite, anorthite, microcline, montmorillonite and illite. The geochemical
composition of groundwater shows the typical fresh water of Ca-HCO3 type.
The unsaturated zone EIT is composed of a subsurface horizontal well and the surface CO2
injection control system. The depth of horizontal well was decided to 2.5m considering previous
cases and conceptual numerical simulation result. A subsurface horizontal well was installed by
trenchless drilling to preserve natural soil condition. The horizontal well has the total length of 51m
with five CO2 release sections. The outer diameter of horizontal well is 100 mm, and that of inlet
tube for individual CO2 feeding is 12 mm. The CO2 injection control system was constructed to
enable the automatic control of injection rate of the individual zones. Also several crops and
seedling were cultivated differently for each zone. The first CO2 release test was performed with the
3 release sections in October 2015. The release period was 4 days (96 hours), and total release
amount is about 390kg of CO2. To observe CO2 migration in subsurface and the environmental
impacts of near surface ecosystems, CO2 concentrations at the depths of 15, 30, 60cm were
measured, and geophysical/geochemical/biological monitoring were carried out in each release zone
from pre (baseline)- to post-injection periods. The CO2 concentration of each zone was varied
differently reflecting the heterogeneity of weathered zone soil. Distinct increases (tens of %) of CO2
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concentration appeared at Zone-3 in 1 day, Zone-4 in 2 days, and Zone-2 in 3 days. After an end of
CO2 release, the movement of CO2 gas plume from south to north was observed. In the subsurface
area of high CO2 concentration, the increase of electrical resistivity was observed immediately after
the CO2 release termination, but the decrease was observed after a few weeks. The impact on plant
and microbe were not observed, and it is estimated to be due too short release time.
The saturated zone EIT consists of an injection well and a few multi-level monitoring wells. We
had planned the injection of saturated groundwater with CO2 into the aquifer and the monitoring of
migration of CO2 and geochemical impact on groundwater downstream the CO2 injection well. The
target aquifer of saturated zone EIT is a weathered zone of 15~30m depth (mainly soil), and CO2
injection well was installed 27m depth with 3m screen interval from bottom. Downstream
groundwater monitoring wells were installed in the bundle shape with 4 different depths (2m screen
section, maximum depth 30m), and had 2.5m intervals along the groundwater flow direction. Also
to detect any CO2 degassing and to monitor its movement from groundwater downstream the CO2
injection well, the gas monitoring wells of unsaturated zone were installed in the shape of multilevel well similar to groundwater monitoring well (but, 1m screen section, maximum depth 14m).
The saturated zone EIT was constructed at the end of 2015, and a preliminary test was not
performed yet.
In 2016, the long-term CO2 release test using the two EIT facilities will be performed to acquire
efficient and accurate monitoring methods of groundwater, soil, atmosphere and biota.
(a) location and arrangement of EIT facilities
(b) vertical section of unsaturated zone EIT
(c) vertical section of saturated zone EIT
<Fig 1> Configuration and vertical section of EIT facilities in Korea
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