25th International Meeting on Organic Geochemistry IMOG 2011

P-022
Open-system hydrous pyrolysis of source rock with continuous
recovery
Martin Stockhausen, Lorenz Schwark
Christian-Albrechts-University - Institute for Geosciences, Kiel, Germany (corresponding
author:mst@gpi.uni-kiel.de)
In order to understand the generation of petroleum
fluids from kerogen under increasing thermal stress,
laboratory pyrolysis procedures have been applied for
several decades. Pyrolysis techniques vary
substantially and can be generally separated into
open versus closed and dry versus hydrous pyrolysis.
Hydrous pyrolysis has been found to mimic natural
processes more closely leading preferentially to
formation of oil-like products, whereas dry pyrolysis
often leads to production of less soluble bitumen not
comparable to free oil. The application of closed
pyrolysis suffers from the formation of primary
generation products, which are subject to subsequent
secondary reactions in the closed system. These
reactions can either break down primary products or
lead to neo-formation from primary compounds by
condensation or recombination reactions.
The combination of hydrous pyrolysis with open
conditions has not been realized routinely. It has thus
been the aim of this study to perform open hydrous
pyrolysis by connecting a continuous recovery system
to a hydrous pyrolysis vessel in order to directly
capture the generated oil/water emulsions and gases.
The water content in the reaction vessel was
maintained stable by adding appropriate amounts of
water via a pump. It is expected that the continuous
recovery of the generated fluids diminishes the effect
of secondary alteration reactions.
Results from the open hydrous pyrolysis experiments
are compared with closed hydrous pyrolysis
experiments applying the same autoclave assembly
(600 ml capacity) for larger sample volumes (50 – 100
g of source rock). In addition smaller volume closed
vessel hydrous pyrolysis using 30 ml reaction tubes
and 500 to 1000 mg of source rock at several
temperatures were conducted for comparison. In the
temperature regime up to 300-320°C differences in
generation yield are small for hydrous and anhydrous
pyrolysis. At temperatures in excess of 300-320°C an
increase in pyrolysis yields under hydrous conditions
occurs. We have thus conducted experiments up to
360°C for hydrous as well as anhydrous pyrolysis
employing small and large volume reactors to
estimate the differences in pyrolyzate formation under
these conditions.
Open system dry pyrolysis was conducted as
reference using Rock Eval techniques. The samples
utilized in the different experiments are chemically
homogenous and derived from a single plate (200 cm
x 100 cm x 5 cm) of Toarcian source rock from the
Dotternhausen quarry in SW-Germany. The thermal
maturity of the sample was 0.4 % Rr, the TOC value
of the starting material was 10.31% TOC, the HI value
was 656 [mgHC/gTOC] and the PI value
corresponded to 0.06.
The data obtained from closed hydrous and
anhydrous pyrolysis, using small and large volume
reactors and those obtained from large volume
continuous open hydrous pyrolysis will be discussed.
This will include mass balances between gases, free
floating oil in the water phase, free oil collected from
the reactor wall and the residual bitumen and also the
analysis of the hydrocarbon compositions.
Fig 1: Schematic setup for an open hydrous pyrolysis
unit with continuous pyrolyzate recovery.
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