Speaker: Arachna Jagadisan, University of Texas at Austin
Speaker Bio:
Arachna Jagadisan, is a Ph.D. student in the Department of Petroleum and
Geosystems Engineering at The University of Texas at Austin. She received her
master's degree in Geological Engineering from Indian Institute of Technology,
Roorkee in 2013. She worked as a Production Geologist and Petrophysicist
at Shell for 3 years. Archana is currently a graduate research assistant at The
University of Texas at Austin under the supervision of Dr. Heidari. Her
research interests include petrophysics of unconventional reservoirs and
geochemistry of organic-rich mudrocks.
EXPERIMENTAL
QUANTIFICATION OF KEROGEN WETTABILITY AS A FUNCTION OF THERMAL MATURITY
Abstract:
Kerogen is often considered to be fully
hydrocarbon-wet in reservoir characterization. Wettability of kerogen
is, however, not well understood and quantified. Thermal maturation induces
changes in the chemical structure of kerogen and alters its oxygen and
hydrogen content. This process affects surface properties of kerogen and
can influence its wettability. Assumptions made about wettability
of kerogen affects interpretation of borehole geophysical measurements
such as electromagnetic measurements. It is therefore important to
quantify wettability of kerogen as a function of its
thermal maturity. The objectives of this paper are to
experimentally quantify wettability of kerogen at different thermal
maturity levels and to quantify the influence of chemical composition of
kerogen on its wettability.
In order to achieve the aforementioned objectives, we first isolated
kerogen from organic-rich mudrock samples from two different formations at
different thermal maturity levels. The extracted kerogen samples are
then synthetically matured and the chemical composition of kerogen is
quantified using XPS (X-ray Photoelectron Spectrometer)
and pyrolysis. We used the sessile drop method to measure the contact
angle, to quantify wettability of kerogen. We then investigated the
impacts of thermal maturity and chemical composition of kerogen on its
wettability.
We tested kerogen samples from two organic-rich mudrock formations (named
A and B) and
demonstrated experimentally that the wettability of kerogen varies with
thermal maturity. Kerogen from formation A at low thermal maturity formed
a 44° contact angle of water. However, at higher thermal maturities
(heat-treated at 650°C) this contact angle of water increased to 122°. We
show that kerogen samples from two organic-rich mudrock formations,
heat-treated at 650°C (high thermal maturity), become oil-wet. The results
suggest that kerogen is hydrocarbon-wet at high thermal maturity and remains
water-wet at low thermal maturity. We also recorded the contact angle in
kerogen samples after removal of bitumen generated during synthetic maturation
of kerogen using chloroform. We demonstrated that contact angle increases from
44° to 90° and from in 111° to 125° with increase in thermal maturity in formations
A and B, respectively. Thus, kerogen becomes hydrocarbon-wet with increasing
thermal maturity both with and without the presence of
bitumen. The outcomes of this paper improve formation evaluation of
organic-rich mudrocks by providing quantitative information on
wettability of kerogen. It can also contribute to correcting the
assumptions made in reservoir simulators developed for organic-rich mudrocks
and can significantly improve our understanding of fluid flow mechanisms in
unconventional reservoirs.
WHEN:
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Morning - Monday, November 26th, 8am – 9am US Central Time;
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