(516e) Spent Shale Formations: Potential Source for CO2 Sequestration

Spent Shale Formations: Potential source for CO₂
Sequestration

Prashanth Mandalaparty, Robert
Krumm and Milind Deo

While producing oil from
shale in-situ, the shale is retorted in the geological formation without mining
to the surface. The objective of the current study is to explore the
possibility of using the (spent) shale repository as a potential source for
geological sequestration of CO₂. For this research, the shale
samples used were retorted at different temperatures in order to address the
following problem:  the response of
different initial mineral matrices and unreacted
organic components to CO₂ injection. 
The experimental apparatus consists of isolated, high-pressure reactors
operated at varying conditions with pure CO₂ as the feed gas.  Initial XRD analysis of the raw and spent
shale samples from Green River formation reveal carbonates, quartz, and
feldspars as the principal inorganic components. Calcite and dolomite
constitute the carbonate sections in the shale and microcline (K-feldspar) and
plagioclase feldspar make up the silicate section. Kaolinite
is present in significant portions and silica is mainly present as quartz. Illite forms the clay portion of the shale. SEM analysis of
the reacted spent shale sample at 100⁰C reveals precipitation of
calcite, magnesite and possibly dolomite. Carbonation
of feldspars was also observed, made evident by the precipitation of carbonates
with their respective principal ions. These changes in rock mineralogy are
complemented by the changes in brine chemistry. Base case kinetic models were
developed using Geo-Chemists Work Bench (GWB). The results from these models
indicate a rapid pace of sequestration reactions when compared to experiments.
Thus this study provides useful laboratory data (with model comparisons) when
considering CO₂ sequestration in different spent shale
repositories.