Transcript Tarik_Saif_Pore-scaleMeeting2015 - Workspace

Pore-Scale Imaging and Analysis
of Oil Shale
Tarik Saif
Supervisors: Prof. Martin Blunt & Dr Branko Bijeljic
12 January 2015
Unconventionals: Oil Shale
What is Oil Shale?
• The term Oil Shale is a misnomer
because it does not contain oil, and is not
always made of shale.
• Instead, rock is actually marlstone (mixture
of clay and calcium carbonate), and the
main organic constituent is kerogen.
• It is a potential petroleum source rock
that would have generated hydrocarbons if
it had been subjected to geological burial
at the requisite temperatures and
pressures for a sufficient time.
Where is Oil Shale found?
Canada
Estonia
UK
France
United
States
Morocco
Russia
Italy
Egypt
Israel
Jordan
China
Zaire
Brazil
Australia
2.8-3.3 Trillion Barrels of Shale Oil Worldwide
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Oil Shale Pyrolysis
• Several complex physical changes occur during the thermal
conversion of kerogen in oil shale to produce hydrocarbons.
• It is (1) the formation of oil and gas resulting from kerogen
decomposition, (2) the creation of pore structure in the shale, (3)
the fluid flow through the pore channels and the ultimate recovery
which are of interest in this research.
• The pore structure and the connectivity of the pore space are
important characteristics which determine fluid flow. A study
investigating the nature of the pores and subsequent permeability
is essential.
Previous Literature
•
X-ray micro tomography has been applied to describe
thermal cracking of Chinese Fushun oil shale at
different temperatures for sample sizes of 7 mm
(Kang et al., 2011).
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A study on the characterisation of oil shale using Xray tomography before and after pyrolysis has also
been presented in recent literature (Tiwari et al.,
2013, Mustafaoglu, 2010).
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However, the exact mechanism of kerogen
decomposition at the pore-scale and the flow
behaviour of the produced oil and gas are unknown.
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Therefore, with improved imaging techniques and
advanced modelling methods this research is
intended to make a valuable contribution to the oil
shale industry.
Before Pyrolysis
After Pyrolysis (500°C,
100°C/min, 24 hours)
Source: Tiwari et al. (2012)
Research Aims & Objectives
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The aim of this research is to describe how oil shale reacts at a given
temperature where kerogen decomposes to produce oil and gas, and to
understand the dynamics of the subsequent two-phase flow through the
pore space created.
As well as temperature (300°C, 400°C, 500°C, 600°C), heating rate (1, 10,
100°C/min), this study will investigate the effects of stress state/lithostatic
load.
The goal is to have a model based on experimental observation of the
physico-chemical mechanisms that govern the process, which will be able
to advise on how the recovery can be optimised.
Emphasis on understanding changes in pore structure and fluid
distribution.
Research Aims & Objectives
Primary sample – Kimmeridge Oil Shale
 Kimmeridge oil shale samples
collected from the cliffs in Dorset
 This oil shale is from the Upper
Jurassic and is the primary sample
for this study
 The Kimmeridge Clay Formation
contains shales with some of the
highest total organic carbon (TOC)
contents 20%+
 Bulk density ~ 1.7g/cm3
Kimmerdige Oil shale – mineral analysis
Mineral
Quartz
Pyrite
Chemical Formula
SiO2
FeS2
Mineral %
10.4
1.3
Oligoclase
Na0.8Ca0.2Al1.2Si2.8O8
14.2
Microcline
KAlSi3O8
3.8
Illite
Calcite
Dolomite
KAl2[AlSi3O8](OH)2
CaCO3
CaMg(CO3)2
6.2
22.8
23.4
Total Organic
Carbon (TOC)
24.2
Micro-CT: before and after pyrolisis
• Sample size: 6mm
• Xradia micro-CT scanner
• Image size: 10003 voxels
Before Pyrolysis
• Pixel size of 1µm
• Exposure time: 10 seconds
• 3200 projections in 11 hours
After Pyrolysis (500°C, 10°C/min, 3
hours)
FIB – Focused Ion Beam
• Helios NanoLab 600
• Uses Ga+ ion beam to
mill a small amount of
material from the
surface
• The generated
secondary electrons (or
ions) are collected to
form an image of the
surface of the sample
• Sample size: 6mm
Nano-CT: dry image
• Photon Energy:
Monochromatic beam,
11.8 keV
• Voxel size: 60 nm
• Exposure time: 15 s
per projection
• Total tomography time:
3 to 4 hours (800
projections)
10 µm
Future work: Imaging
Heating Oil Shale - Furnace
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Furnace has capability to reach ~ 1400°C.
Heating rates of 1, 10 and 100°C/min to be tested.
10mm holes on either side of the furnace to allow
penetration of X-rays for imaging.
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Two ceramic end caps placed on either end for a
closed system.
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Ex-situ experiments to be
performed initially.
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In-situ experiments to be
performed at a later stage.
Future work: Modelling
 Modelling the kerogen decomposition to produce oil and gas and the flow
of the fluids through the created pore structure using pore network
modelling and also a Finite Volume method.
The research questions to be answered include:
1. Does the solid-fluid conversion occur at the rock matrix-kerogen
interface, at the centre of the organic matter, or randomly?
2. What is the percolation threshold point at which the pores become
connected?
3. What are the changes in fluid distribution as pyrolysis progresses?
 The network will be periodically updated by extracting it over selected
times. Initially, the parameters studied will include pore size distribution,
connectivity (topological), and the rate of fluid formation as a temperature
dependence.
Pore-Scale Imaging and Analysis of Oil Shale
Thank You!
Tarik M. A. Saif
PhD Student (Petroleum Engineering)
Earth Science and Engineering Department
Imperial College London
Email: [email protected]
References

Aboulkas, A., & El Harfi, K. (2008). Study of the kinetics and mechanisms of thermal decomposition of
Moroccan Tarfaya oil shale and its kerogen. Oil shale, 25(4), 426-443.

Doan VL., (2011). Oil Shale Pyrolysis Laboratory & Technique. Oil Shale Symposium.

Han X., Xiumin J., Lijun Y., Zhigang C., (2006). Change of pore structure of oil shale particles during
combustion. Part 1. Evolution mechanism. Energy Fuels; 20, 2408-12.

Kang Z., Yang D., Zhao Y., Hu Y., (2011). Thermal cracking and corresponding permeability of
Fushun oil shale. Oil shale; 28, 273-83.

Külaots, I., Goldfarb, JL., & Suuberg, EM., (2010). Characterization of Chinese, American and
Estonian oil shale semicokes and their sorptive potential. Fuel, 89(11), 3300-3306.

Lin CL., Miller JD., (2011). Pore scale analysis of Oil Shale/Sands pyrolysis. Prepared for the United
States Department of Energy and the National Energy Technology Laboratory. Oil & Natural Gas
Technology.
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Mustafaoglu O., (2010). Charactrization and pyrolysis of oil shale samples: An alternative energy
option. LAP Lambert Academic Publishing.

Nazzal, JM., (2002). Influence of heating rate on the pyrolysis of Jordan oil shale. Journal of analytical
and applied pyrolysis, 62(2), 225-238.

Tiwari, P., Deo, M., Lin, CL. & Miller, JD., (2012). Characterization of Core Pore Structure Before and
After Pyrolysis using X-ray Micro CT. Fuel, 2013, 107, 547-554.

Williams PT., Ahmad, N., (1999). Influence of process conditions on the pyrolysis of Pakistani oil
shales. Fuel, 78(6), 653-662.