Transcript Studies on quartz as the tracer of fluid migration

Fluid inclusion studies in search
for hydrocarbons in marine and
mountain regions
Katarzyna Jarmołowicz-Szulc
POLISH GEOLOGICAL INSTITUTE
CENTRE OF EXCELLENCE
Research on Abiotic Environment
REA
Objectives
The aims of the presentation are:
- to show characteristic features of fluid
inclusions in the quartz and in the quartz
cements
- to interpret the results of the isotope,
microthermometry and fluorescence studies in
the context of fluid evolution and formation of
the rocks.
Quartz - one of the best known and studied minerals in the world has been occurring in different geological environments, in that as
the cement in the sedimentary rocks in the hydrocarbon reservoirs ,
as well as the vein mineral of certain characteristics
called the Marmarosh diamonds.
Localization and structures
The Marmarosh diamonds
• The second variety of the
quartz mentioned, has
been studied for about a
century in the
Carpathians in Europe ,
aiming at explanation of
the phenomena of its
formation and
characteristics
(Tokarski, 1905; Hurai
et al., 1989; Dudok et al.,
1997; JarmolowiczSzulc, 2001a).
Methods used
• Double-sided-polished thin sections of the sandstones, and quartz
crystals themselves, were prepared for fluid inclusion studies using
two preparation techniques (Jarmołowicz-Szulc 2001a,b).
• The microscopic studies performed in the Petrological Department of
the Polish Geological Institute in Warsaw, Poland comprised:
• - a microscope analysis of fluid inclusions (Leitz Orthoplan);
• - fluorescence studies together with a microphotography (Nikon
microscope and UV device);
• - cold cathodoluminescence studies (CCL 8200 mK3);
• - microthermometric analyses (homogenisation and freezing using
Fluid Inc. System).
Inclusions in the
quartz cement
•
Occur in the early and late
quartz cements. HCFI
display fluorescence in
white – blue colour. Oil is
light and mature. Densities
from 41 to 45°API . AQFI
are at the boundary of the
detrital and the authigenic
quartz, in the early cement
and in the late filling of
microfractures. The HCFI
are most frequent in the
late filling of the fissures.
Isotope studies in quartz
overgrowths & detrital grains
Quartz overgrowths
studied by means of
SIMS point method
display delta oxygen
values in the interval of
23.0 to 25.6 per mille.
Results for sandstones
• The AQFI are at the
boundary of the detrital
and the authigenic quartz,
in the early cement and in
the late filling of
microfractures. The
hydrocarbon inclusions
are most frequent in the
late filling of the fissures,
thus pointing out the late
hydrocarbon migration to
the reservoir
Conclusions
• Oil is present in the late
cements in the Cambrian
sandstones, mostly in the
fillings
of
tectonic
microfractures and stylolitic
sutures. It migrated together
with water and was trapped
in the late quartz in the
conditions of 107C and
317 bars. It is light and
mature. The abundance of
HCFI is restricted to some
boreholes and the upper
parts of the profiles.
Features of the Marmarosh
diamonds
The isotope studies were conducted by means of the method of a point
analysis in quartz.
SIMS isotope analysis of the oxygen was performed at the Arizona State
University in Tempe (AZ, USA) – the procedure of Hervig et al. (1992)
and Williams et al. (1997). Three grains of quartz (the Marmarosh
diamonds) have been studied.
Isotopic point analysis in quartz
(the Marmarosh diamonds)
• The δ 18OSMOW values
for quartz range from
15.7‰ and 26.7‰
(SIMS).
• Data for the crystals
from the eastern part
are most scattered and
lower.
• Average
The Marmarosh diamonds from the
Western and Eastern Carpathians
• Represent a type of the bi-pyramidal quartz
in euhedral, transparent crystals of an ideal
crystal habit and a perfect reflection
(Karwowski & Dorda, 1974). The
inclusions in this type of quartz are either of
primary or of secondary origin.
Presentation of types of
inclusions
Presentation of types of
inclusions
The first type of the quartz filling in the porous space has been the object
of numerous petrological analyses for long years (e.g. Sikorska &
Paczesna, 1997). The present case concerns the Cambrian sandstones from
the Polish segment of the Baltic Sea, which are the reservoir rocks for oil
Microthermometry results and
interpretation for the Marmarosh
diamonds
Fluid iclusions
• The quartz crystals come from the
tectonic zones and contain a
spectrum of fluids - from methane,
through oil to aqueous solutions.
Conclusions
• The fluid inclusions and isotopic studies in both
the quartz cement and the quartz crystals point to
the hydrocarbon migration and the character of the
palaeofluids responsible for the cement formation
and/or the quartz crystallisation.
• The areas of the occurrence of the hydrocarbons in
the inclusions in the quartz may be mostly
prospective for the search for oil and gas
Thank you!