Environmental Engineering Reference
In-Depth Information
500
400
300
200
100
0
-100
-200
-300
-400
-500
Eh2MP (S3)
Eh4MP (S5)
Eh5MP (S9)
Eh5OP (S10)
3.5
13.5
23.5
2.6
12.6
Time (days)
VIL + Eh
Change of redox signals due to oxygen gas injection
MIDZ
FIGURE 10.9
Gas monitoring devices for RGBZ and gas sensing signals (data from BIOXWAND).
(VIL + Eh—loosen sonic lance filter with redox sensor; MIDZ—flow-through shuttle).
sensor value changes on the cessation of gas injections can be interpreted as
the propagation of incoherent gas clusters and gas dissolution.
Another method for the estimation of gas propagation is trace gas testing;
currently the best available are found to be noble gases (e.g., He, Ne, and Ar).
Trace gases are mixed with a carrier gas and injected at low partial pres-
sures. Due to a lack of interaction with soil and groundwater, environmental
authorities have accepted the use of noble gases. Care is needed during trace
gas sampling due to their high volatility. The use of pressurized samplers or
bailers is also recommended (Uhlig, 2010 and Schinke, 2008).
10.3.3.3 Gas Saturation Testing
To estimate the amount of stored reactive gaseous substances, a gas satu-
ration test that takes pressure dependency into account is required. The
best available techniques for gas saturation estimations are (1) gas-hydro-
geological balancing injection gas models, (2) direct gas profiling, and (3)
local pumping tests in gas storage regions. Aqueous and partitioning trace
gas infiltration methods are time-consuming and are currently still under
evaluation.
Oxygen gas balance models can be parameterized using laboratory tests
and gas monitoring. These models are suitable for the estimation of mean
gas saturations in large gas storage zones, or layers during stationary oper-
ation periods (Ehbrecht and Luckner, 2004; Weber, 2007). The first step is
to estimate the geometry of the storage zones, using gas-hydrogeological
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