Carbon Dioxide Seal Capacity Study, Boggy Creek, Otway Basin, Victoria Daniel, Dr. R.F.

Transcription

1

2

3 Carbon Dioxide Seal Capacity Study, Boggy Creek, Otway Basin, Victoria Daniel, Dr. R.F. September 2005 CO2CRC Report No: RPT

4 Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) GPO Box 463 Level 3, 24 Marcus Clarke Street CANBERRA ACT 2601 Phone: Fax: pjcook@co2crc.com.au Web: Reference: Daniel, R.F., 2005, Boggy Creek Carbon Dioxide Seal Capacity Study, Otway Basin, Victoria, Australia. CO2CRC Publication No RPT , August 2005, 47pp CO2CRC 2005 Unless otherwise specified, the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) retains copyright over this publication through its commercial arm, Innovative Carbon Technologies Pty Ltd. You must not reproduce, distribute, publish, copy, transfer or commercially exploit any information contained in this publication that would be an infringement of any copyright, patent, trademark, design or other intellectual property right. Requests and inquiries concerning copyright should be addressed to the Communication Manager, CO2CRC, GPO Box 463, CANBERRA, ACT, Telephone:

5 Table of Contents Executive Summary...2 Introduction...3 Methodology...4 Mercury Injection Capillary Pressure (MICP)...4 Pore Throat Size Distribution...5 Determination of Seal Capacity...6 Otway Basin Subsurface fluid properties:...7 Results...8 Discussion and Conclusions...10 References...12 Appendix...13 Scanning Electron Microscopy...13 XRD Mineralogy...22 Graphs of; (A) Injection Pressure vs. Hg Saturation and Incremental Pore Volume, (B) Pore Throat Size vs. Frequency and (C) CO2 Seal Capacity above FWL vs. Water Saturation...28 Table of Figures Table 1 Data available on samples from Boggy Creek 1 and Flaxmans Table 2 Primary and derived data used to determine the carbon dioxide column height... 8 Figure 1: Carbon dioxide retention heights for samples from Boggy Creek 1 and Flaxmans 1. Samples analysed by the Australian School of Petroleum Table 3: Spatial distribution of depositional environment analogues for sealing lithologies (after R. Root, 2004) Figure 2 Analogue for Area / Thickness and Length / Width for sealing rock depositional environments after Root in Daniel et al., 2003 and Root et al., Figure 3 SEM of Boggy Creek Waarre Formation Figure 4 - SEM of Boggy Creek Waarre Formation Figure 5 - SEM of Boggy Creek Waarre Formation Figure 6 - SEM of Flaxmans Belfast Mudstone Figure 7 - SEM of Flaxmans b Flaxman Formation Figure 8 - SEM of Flaxmans Flaxman Formation...19 Figure 9 - SEM of Flaxmans Waarre Formation Figure 10 - SEM of Flaxmans Waarre Formation Table 4: Bulk mineralogy of sealing rock samples (M. Raven CSIRO) Figure 11: XRD mineralogy Boggy Creek Figure 12: XRD mineralogy Boggy Creek Figure 13: XRD mineralogy Boggy Creek Figure 14: XRD mineralogy Boggy Creek Figure 15: XRD mineralogy Flaxmans Figure 15: XRD mineralogy Flaxmans Figure 16: XRD mineralogy Flaxmans Figure 17: XRD mineralogy Flaxmans Figure 18: XRD mineralogy Flaxmans

6 Executive Summary Core samples from the Belfast Mudstone and Flaxman Formation regional seals and intraformational seals from the Waarre Formation are analysed for their capacity to retain or support a column carbon dioxide in the subsurface as part of the Otway Basin Pilot Project (OBPP). The samples are from Boggy Creek 1 and Flaxmans 1, which are in the region of the project and the closest wells, which are cored through the zones of interest. This report details the result of MICP (Mercury Injection Capillary Pressure) analyses, scanning electron microscopy (performed at the Australian School of Petroleum) and XRD mineral analyses (CSIRO) on these sealing samples. Capillary pressure data are used to determine threshold or break through pressure, which is used in the calculation of the carbon dioxide retention height of sealing rocks. Pore throat size distributions are also plotted for the analysed samples and the laboratory mercury/air values are converted to subsurface supercritical carbon dioxide values to determine saturation versus height relationships. The carbon dioxide seal retention column for the sample of the Belfast Formation is approximately 840 m, the Flaxman Formation CO2 column height varies between 713 to 987 m and the intraformational seal of the Waarre Formation column height between 0.16 and 1631 m. Mudstones and claystones of the Belfast Mudstone, Flaxman and Waarre Fms in the Boggy Creek 1 and Flaxmans 1 area represent depositional environments from prodelta shelf to upper deltaic coastal shoreface to braided fluvial overbank (intraformational seal) (Faulkner 2000) and an indication of coverage of these depositional environments is provided by ancient and modern analogue data. The areal distribution of these depositional environment analogues vary from 350 to 5,000 km 2 (Belfast Mudstone), 1 to 100 km 2 (Flaxman Formation) and the analogue data for the Waarre Formation varies from 0.4 to 3 km 2. 2

7 Introduction The Otway Basin in the region of Boggy Creek in Victoria is the subject of a pilot injection study to determine the viability of storing super critical carbon dioxide in the partially depleted Waarre C hydrocarbon reservoir. This reservoir is capped by regional sealing lithologies of the Belfast Mudstone and the Flaxman Formation and samples from these formations are the subject of MICP analysis to determine the carbon dioxide seal capacity or retention height. Intraformational seals from the upper Waarre Formation are also analysed to determine the potential for baffling the migration CO 2. Background data for column height determination were obtained from the well completion reports of Boggy Creek 1 and Flaxmans 1. Super critical carbon dioxide saturation versus height and seal retention height were determined from the MICP analyses and these data. An outline of mercury injection capillary porosimetry and the determination of pore throat size and seal capacity is presented under Methodology. Table 1 provides details of the samples analysed. Table 1 Data available on samples from Boggy Creek 1 and Flaxmans 1 Well Depth (m) Formation Core/ Cuttings/ SWC Boggy Creek Waarre Formation Core Boggy Creek Waarre Formation Core Boggy Creek Waarre Formation Core Boggy Creek Waarre Formation Core Flaxmans Belfast Mudstone Core Flaxmans b Flaxman Formation Core Flaxmans Flaxman Formation Core Flaxmans Waarre Formation Core Flaxmans Waarre Formation Core 3

8 Methodology Mercury Injection Capillary Pressure (MICP) The theory of the mercury porosimeter is based on the physical principle that a non-reactive, non-wetting liquid will not penetrate pores until sufficient pressure is applied to force its entrance. The relationship between the applied pressure and the pore throat size into which mercury will intrude is given by the Washburn equation (1921): P c D = 4 γ cos θ (1a) More recently, however, this equation has developed into a more useful style for determining pore throat radius as suggested by Purcell (1949) and Schowalter (1979): P c r = 2 γ cos θ (1b) Where P c is the applied capillary pressure, D is the pore throat diameter, r is the pore throat radius, γ is the surface tension of mercury (480 dyne cm -1 ) and θ is the contact angle between mercury and the pore wall, usually near 140. This equation assumes that all pores are right circular cylinders. As pressure increases, the instrument senses the intrusion volume of mercury by the change in capacitance between the mercury column and a metal sheath surrounding the stem of the penetrometer. As the mercury column shortens, the pressure and volume data are continuously acquired by an attached computer. Mercury porosimetry is a technique, which is rate limited, as predicted by the Darcy equation. This describes the general function of pressure drop vs. flowrate: ρ1 ρ 2 L αµ V = g c (2) Where ρ 1 is the upstream pressure, ρ 2 is the downstream pressure, L is the pore length, 1/α is the permeability coefficient, µ is the fluid viscosity, V is the superficial velocity of fluid and g c is a dimensional constant. The velocity of flow in a viscous liquid such as mercury is proportional to the pressure drop and inversely proportional to the length and surface area of the pore. Hence, given a specific limited flow velocity, the complete filling of a porous network will be a function of time. The larger the volume of pores the more time is required to fill the total pore volume completely. Therefore mercury porosimetry is most accurate when mercury is allowed to fill all the available pores, at equilibration. The mercury injection porosimetry analyses for this study were carried out using a Micromeritics Autopore 9410 instrument. This is composed of two separate systems, one for low pressure runs and the second for the high pressure runs. The low pressure run must always be done first, followed quickly by the high 4

9 pressure run, to preclude the possibility of extra mercury intrusion into the sample by capillary action while the sample is held at atmospheric pressure at the conclusion of the low pressure run. The system operates using the equilibration by time method - after the required pressure for a reading is attained it is held for twenty seconds to allow the amount of mercury entering the pores to stabilise. This is done because the process of mercury filling the pores is not an instantaneous one. Mercury begins entering the pores as soon as the pressure exceeds the value required for the pore throats' diameter, but the time required to fill the pores depends on the volume and shape of the pores. The equilibration by time process allows the pores to fill. If equilibration is not allowed, then the filling may not be complete when the reading is taken, which leads to estimation of lower pore volumes and smaller pore sizes than is actually the case. Readings of mercury intrusion are taken by measuring the electrical capacitance of the penetrometer. This varies as the mercury is intruded from the precision bore stem into the pore space of the sample by the increasing pressure. Each sample is usually dried at 60 o C for at least twenty four hours, weighed and placed into a penetrometer (a glass chamber attached to a precision bore glass tube, which has been nickel-plated) and the entire assembly is weighed. This is placed in the low pressure port and evacuated to 0.05 torr. This vacuum is held for thirty minutes to ensure that no vapour remains in the sample. After this time the penetrometer is filled with mercury and the low pressure run is carried out. The pressure is increased incrementally from 13.8 kpa (2 psia) to kpa (28.94 psia), with a reading taken after 20 seconds of equilibration at each pressure. At the end of the low pressure run the penetrometer returns to atmospheric pressure. It is removed from the instrument and weighed to obtain its weight plus that of the mercury. The penetrometer is then placed in the high pressure chamber, which uses hydraulic oil to take the pressure incrementally from kpa (28.94 psia) to MPa (60,000 psia). Again readings are taken after a twenty second equilibration period (see Graph A of the first three analyses). The pressure then decreases incrementally from MPa (60,000 psia) to 139kPa (20 psia), with readings taken after the equilibration period. The sample is removed from the penetrometer and weighed. The specific gravity and porosity of the sample can be calculated when it is removed from the penetrometer and weighed. Pore Throat Size Distribution Using the following data for the air mercury system from (Vavra et al, 1992), capillary pressure data were converted to effective pore throat size: Air/mercury contact angle (θa/m) = 140, and interfacial tension (σa/m) = 480 dynes/cm. σ(a/m) cos θ(a/m) = cm = 10,000 µ, 1 psi = dynes/cm2 5

10 Solving for r in equation (1b) results in the following relationship of capillary pressure to pore throat size: 1 psi = (approx.) 100 microns 10 psi = (approx.) 10 microns 100 psi = (approx.) 1 micron 1000 psi = (approx.) 0.1 micron (see Graph B of the first three analyses in the Appendix) Determination of Seal Capacity MICP studies done solely for the purpose of determining pore throat radius and pore throat size distribution are valuable. However, there is great benefit in using the MICP analytical data to relate the mercury saturation of the sedimentary rock to the intruding pressure as a function of height above the free water level (FWL). This function indicates the CO 2 column height that a sealing rock will support. The processes of determining column height is described below. Before the mercury injection data can be applied to seal capacity they must be converted to a subsurface CO 2 /brine system using the following equation (after Schowalter, 1979): P bco a / m ( σ cosθ ) bco ( σ cos ) a / m b / CO 2 2 = P (3) 2 θ Where PbCO 2 is the capillary pressure in the brine/co 2 system, P a / m is the capillary pressure in the air/mercury system, σ bco 2 and σ a / m are the interfacial tensions of the brine/co 2 and the air mercury systems respectively, θ b / CO 2 and θ a / m are the contact angles of the brine/co 2 /solid and air/mercury/solid systems respectively. a / m The initial pressure at which the mercury first displaces the air is referred to as the "displacement pressure" (Pd). In the subsurface, buoyancy pressure drives CO 2 (the non-wetting phase) movement and forces it into the pore throats of a rock, displacing water (the wetting phase). Buoyancy is simply the density difference between CO 2 and brine multiplied by the column height and a constant (k) gravitational factor, which is The greater the column thickness, the greater the buoyancy pressure driving the CO2. Pd in the reservoir system is the pressure at which CO2 first entered the pore system by displacing the water. Different rocks with different pore throat sizes will have different displacement pressures and different saturations as a function of height (h) above the free water level (FWL). Thus, in any given 6

11 reservoir section, the lowest indication of live (vs. residual) CO 2 in a particular rock type approximates the displacement pressure (Pd) for that rock. The Pd can thus be considered as the CO 2 water contact for that particular rock type. It should be remembered that a reservoir may have several CO 2 water contacts (as a function of pore properties controlled by rock type), but will have only one FWL. It is therefore of significance to determine the FWL. In order to do this, capillary pressure data must first be converted to height above free water level information by using the equation: Pc b/co2 = h(ρb-ρco 2 ) x (4) Where: Pc b/co2 = Capillary Pressure (psi) reservoir brine/co 2 system h = height (in ft.) ρb = brine density (gm/cc) ρco 2 = CO 2 density (gm/cc) Otway Basin Subsurface fluid properties: Super critical CO 2 Density to 0.70 gm/c 3 (variable ) Brine Density- variable in the range of 1.01 to gm/c 3. Interfacial Tensions were determined from the CO2CRC web-site carbon dioxide calculator (see Table 2 for the parameters of each sample). Generally the interfacial tension for brine/co 2 is approximately 26 dynes/cm and the contact angle is 0 as shown below. System Contact angle ( Interfacial tension ( ) Brine/CO dynes/cm (variable) Air/mercury dynes/cm Once the capillary pressure values have been converted to h (height in metres), a plot of height versus mercury (non-wetting phase) saturations can be constructed. However, conversion of mercury (non-wetting phase) to CO2 (non-wetting phase) will now result in a height versus CO2 saturation plot. Since water (wetting phase) saturation is more commonly used in the oil and gas industry, the non-wetting phase saturation needs to be converted to water (wetting-phase) saturation (Schowalter, 1979). This is done using the simple conversion: 7

12 Sw = 1 Snw (5) Where: Sw = wetting phase (water) saturation Snw = non-wetting phase (CO2) saturation Combining equations (4) and (5) result in a plot of height (above FWL) versus water saturation as highlighted in the third graph (C) shown of each sample (see Graph C of the first three analyses in the Appendix) Results The carbon dioxide seal retention column of the Belfast Formation is calculated to be approximately 840 m from MICP analysis in Flaxmans 1. The Flaxman Formation CO 2 column height varies between 713 to 987 m in Flaxmans 1. The Waarre Formation column height varies between 0.16 and 1631 m in Boggy Creek 1 and 15 to 101 m in Flaxmans 1 (Table 2 and Figure 1). Table 2 Primary and derived data used to determine the carbon dioxide column height. 8

13 0.16 m Figure 1: Carbon dioxide retention heights for samples from Boggy Creek 1 and Flaxmans 1. Samples analysed by the Australian School of Petroleum. 9

14 Discussion and Conclusions CO 2 retention heights in these samples vary with relative clay vs sand content and the presence of partially dissolved feldspars. The four samples with lower retention values all featured a significant medium to very fine grain sand fraction with partial dissolution of feldspar grains. The surfaces of these comparatively larger grains and the partially dissolved grains may act as larger capillary conduits for fluids moving through the formation leading to a reduced retention height. These reductions are occurring only in the Waarre Formation and not the regional seals and hence will act as baffles and increase the potential for mineralogical storage of carbon dioxide. The mudstones and claystones of the Belfast Mudstone represent a prodelta to open shelf depositional environment. Sediments of the Flaxman Formation is attributed to a lower delta to restricted shallow marine depositional environment and the Waarre Formation to a braided fluvial complex with overbank deposits acting as intraformational seals (Faulkner 2000). An indication of coverage of the above depositional environments is provided by ancient and modern analogue data of varying depositional environments (Figure 2). These depositional environment analogues have areal distributions of 350 to 5,000 km 2 (Belfast Mudstone), 1 to 100 km 2 (Flaxman Formation) and the analogue data for the Waarre Formation intraformational seals vary from 0.4 to 3 km 2 (Table 3). Table 3: Spatial distribution of depositional environment analogues for sealing lithologies (after R. Root, 2004) Depositional Lithology Spatial Distribution Environment Area km 2 Package Thickness m Prodelta Mudstone - claystone 1 5,000 ~2 Upper Delta Plain Very fine sand to silty mudstone Fluvial Overbank Vfg sandstone - mudstone Previous investigations of seal capacities within the Otway Basin in the Shipwreck Trough area show that the Belfast Formation can support columns of SC CO2 between 580 and 1100 m (5 samples). The Flaxman Formation retention column varies between 20 and 1400 m (5 samples) and the Waarre Formation intraformational seals between 180 and 1900 (2 samples). 10

15 ,000 10, ,000 Figure 2 Analogue for Area / Thickness and Length / Width for sealing rock depositional environments after Root in Daniel et al., 2003 and Root et al.,

16 References Boyd, G.A. and Gallagher, S.J., The sedimentology and palaeoenvironments of the late Cretaceous Sherbrook Group in the Otway Basin. PESA Eastern Australian Basins Symposium p Buffin, A.J., Waarre Sandstone development within the Port Campbell embayment. APEA Journal, 1989, p., Dewhurst, D.N., Jones, R.M., and Raven, M.D., Microstructural and petrophysical characterisation of Muderong Shale; application to top seal risking. Petroleum Geoscience V 8, p Daniel, R.F., and Kaldi, J.G., Atlas of Australian and New Zealand Hydrocarbon Seals. Volume 3, APCRC Technical Workshop Proceedings, Program 1; Hydrocarbon Sealing Potential of Faults and Cap Rocks. Perth, WA, June p Faulkner, A., Sequence stratigraphy of the late Cretaceous Sherbrook Group, Shipwreck Trough, Otway Basin. Honours Thesis, National Centre for Petroleum Geology and Geophysics, The University of Adelaide. Kaldi, J.G., O Brien, G., and Kivior, T., Seal capacity and hydrocarbon accumulation history in dynamic petroleum systems: the East Java Sea, Indonesia, and the Timor Sea, Australia. APPEA Journal V.39. Kivior, T., Kaldi, J.G. and Lang, S.C., Seal potential in Cretaceous and late Jurassic rocks of the Vulcan Sub-Basin, northwest shelf Australia. APPEA Journal V 42, p Purcell, W.R., Capillary pressures their measurement using mercury and the calculation of permeability therefrom. Petroleum transactions, American Institute of Mining, Metallurgical and Petroleum Engineers, v. 186, p Root, R.S., Gibson-Poole, C.M., Lang, S.C., Streit, J.E., Underschultz, J. and Ennis-King, J., Opportunities for geological storage of carbon dioxide in the offshore Gippsland Basin, SE Australia: An example from the upper Latrobe Group. In Boult, P.J., Johns, D.R. and Lang, S.C. (Eds), Eastern Australasian Basins Symposium II, Petroleum Exploration Society of Australia, Special Publication, p Schowalter, T.T., Mechanics of secondary hydrocarbon migration and entrapment. AAPG Bulletin v. 63, p Sneider, R.M., Practical petrophysics for exploration and development. AAPG Continuing Education Short Course Notes. Wardlaw, N.C., The effects of pore structure on displacement efficiency in reservoir rocks and in glass micromodels. In: 1 st joint SPE/DOE Symposium on Enhanced Oil Recovery, SPE no. 8843, p Wardlaw, N.C., and M. McKellar, Mercury porosimetry and the interpretation of pore geometry in sedimentary rocks and artificial models. Powder Technology v. 29, p

17 Appendix Scanning Electron Microscopy 13

18 Figure 3 SEM of Boggy Creek Waarre Formation a) General view of an intraformational seal within the upper Waarre Formation showing coarse quartz and remnant feldspar grains in a matrix of smectite, muscovite and kaolinite View oblique to bedding. Scale 50 µm b) Microporous framboids of pyrite are common throughout the matrix (see insert) View oblique to bedding. Scale 20 µm c) The matrix is composed of dominantly smectite, illite and kaolinite. Framboids of pyrite upper left. Rhomb of siderite arrowed View oblique to bedding. Scale 10 µm d) Rhombs of siderite encapsulated in a smectite / kaolinite matrix View oblique to bedding. Scale 10 µm q e) EDS spectrum indicates abundant clays with silica and trace anatase (Ti) with siderite and pyrite (Fe). f) Larger grains of muscovite and occasional quartz are highlighted along the bedding plane. View parallel to bedding. Scale 20 µm 14

19 Figure 4 - SEM of Boggy Creek Waarre Formation a) General view of an intraformational seal within the upper Waarre Formation highlighting a matrix of kaolinite and muscovite View perpendicular to bedding. Scale 100µm b) Very fine silty grains of quartz throughout the kaolinite and muscovite matrix. View perpendicular to bedding. Scale 50µm c) Detail of muscovite within the clay matrix View perpendicular to bedding. Scale 20µm d) EDS spectrum indicates silica, kaolinite, minor pyrite. High sulphur due to jarosite (see XRD) e) Elongate grains of mica in a kaolinitic matrix View oblique to bedding. Scale 20µm f) Very fine grained matrix of kaolinite and jarosite with minor pyrite View oblique to bedding. Scale 50µm 15

20 Otway Basin Pilot Project, Seal Capacity Figure 5 - SEM of Boggy Creek Waarre Formation f p a) General view of an intraformational seal within b) Quartz with partially dissolved feldspar and the upper Waarre Formation highlighting fine pyrite molds in the matrix. grained quartz in a kaolinite matrix View oblique to bedding. Scale 50µm View oblique to bedding. Scale 100µm c) Detail of partially dissolved K feldspar showing intra granular microporosity (see insert) View oblique to bedding. Scale 20µm d) EDS spectrum indicating silica, clays, feldspar and pyrite (NB high sulphur) e) General view of overlapping platelets of clay indicating a good sealing lithology View perpendicular to bedding. Scale 50µm f) Detail of overlapping platelets highlighting very low microporosity. View perpendicular to bedding. Scale 5µm 16

21 Otway Basin Pilot Project, Seal Capacity Figure 6 - SEM of Flaxmans Belfast Mudstone a) General view of the Belfast Mudstone, regional seal, highlighting tightly packed matrix View perpendicular to bedding. Scale 50µm b) Detail showing large overlapping clay platelets with little microporosity visible. View perpendicular to bedding. Scale 20µm c) Detail of smectite, illite and kaolinite in the matrix View perpendicular to bedding. Scale 2µm d) EDS spectrum indicates clays with silica and trace feldspar and pyrite. e) View parallel to the bedding shows more micro-porosity and also that the overlapping clay platelets would inhibit flow across the bedding (arrow direction) View parallel to bedding. Scale 20µm f) Detail a large flake of mica with small pyrite framboids in the clay packages. View parallel to bedding. Scale 5µm 17

22 Otway Basin Pilot Project, Seal Capacity Figure 7 - SEM of Flaxmans b Flaxman Formation a) General view of Flaxmans Formation sample showing coarse quartz sand in a very fine matrix Scale - 500µm b) Detail of a rounded quartz grains with very fine grained matrix. Scale 20µm c) Detail of the matrix highlighting a combination of berthierine and siderite with fine grained mica Scale 2µm d) EDS spectrum indicates silica and clay/mica with siderite and berthierine (XRD). e) Microporosity is abundant in areas where there is a lack of siderite and berthierine is common Scale 5µm f) Foliated muscovite platelets among berthierine and rhombs of siderite Scale 2µm 18

23 Figure 8 - SEM of Flaxmans Flaxman Formation a) General view of Flaxmans Formation seal showing fine quartz sand and mica flakes in a very fine matrix. View oblique to bedding. Scale 50µm b) EDS spectrum indicates silica, clays/mica, pyrite and calcite with trace anatase (Ti). c) Detail of common quartz and mica grains throughout the matrix. View oblique to bedding. Scale 10µm d) Matrix detail of kaolinite smectite and mica with View oblique to bedding. Scale 5µm e) Large grains of muscovite in clay matrix with microporosity evident between the platelets View perpendicular to bedding. Scale 20µm f) Detail of smectite / kaolinite matrix with vfg berthierine and pyrite between the clay platelets View perpendicular to bedding. Scale 10µm 19

24 Otway Basin Pilot Project, Seal Capacity Figure 9 - SEM of Flaxmans Waarre Formation a) General view of Waarre Formation intraformational seal showing coarse quartz sand grains in a very fine matrix. View parallel to bedding. Scale 500µm b) Detail of the kaolinite and muscovite matrix between quartz grains View parallel to bedding. Scale 50µm c) Detail of feldspar dissolution with chlorite / berthierine development View parallel to bedding. Scale 20µm d) EDS spectrum indicates abundant silica with kaolinite chlorite/berthierine, mica and feldspar. e) View of large flake of muscovite with kaolinite and minor quartz. View perpendicular to bedding. Scale 50µm f) Detail of muscovite and kaolinite matrix highlighting large overlapping platelets View perpendicular to bedding. Scale 20µm 20

25 Otway Basin Pilot Project, Seal Capacity Figure 10 - SEM of Flaxmans Waarre Formation b) Detail of sub-laminar matrix between the quartz grains. View oblique to bedding. Scale - 50µm. a) General view of Waarre Formation intraformational seal showing coarse quartz sand grains in a very fine matrix. View oblique to bedding. Scale 500µm Kf m b c) Very fine clay matrix between the quartz provides sealing qualities although microporosity is present at the sub-micron level. View oblique to bedding. Scale - 10µm. e) EDS spectrum indicates silica, clays, feldspar and minor pyrite 21 d) Detail of muscovite (m), K feldspar (Kf) and berthierine/chlorite (b). View oblique to bedding. Scale - 2µm. f) Detail shows large overlapping platelets kaolinite and muscovite with small grains of feldspar View perpendicular to bedding. Scale - 5µm.

26 XRD Mineralogy Table 4: Bulk mineralogy of sealing rock samples (M. Raven CSIRO) 22

27 BC-1673 Bulk QUARTZ, SYN MONTMORILLONITE-15A SIDERITE PYRITE KAOLINITE-1A MUSCOVITE-2M1 20 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13670blk.101 Figure 11: XRD mineralogy Boggy Creek BC Bulk QUARTZ, SYN PYRITE KAOLINITE-1A MUSCOVITE-2M JAROSITE, SYN 36 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13672blk.103 Figure 12: XRD mineralogy Boggy Creek

28 BC Bulk QUARTZ, SYN PYRITE KAOLINITE-1A MUSCOVITE-2M HEMATITE, SYN GYPSUM, SYN JAROSITE, SYN MICROCLINE, INTERMEDIATE Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13673blk.104 Figure 13: XRD mineralogy Boggy Creek BC Bulk QUARTZ, SYN PYRITE KAOLINITE-1A MUSCOVITE-2M MICROCLINE, INTERMEDIATE HEMATITE, SYN JAROSITE, SYN 70 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13674blk.105 Figure 14: XRD mineralogy Boggy Creek

29 Fl-6385 Bulk QUARTZ, SYN PYRITE KAOLINITE-1A MUSCOVITE-2M MONTMORILLONITE-15A BERTHIERINE-1M 36 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13677blk.108 Figure 15: XRD mineralogy Flaxmans Fl-6630a Bulk QUARTZ, SYN KAOLINITE-1A MUSCOVITE-2M SIDERITE CALCITE, SYN MICROCLINE, INTERMEDIATE BERTHIERINE-1M Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13678blk.109 Figure 15: XRD mineralogy Flaxmans

30 Fl-6835 Bulk QUARTZ, SYN KAOLINITE-1A MUSCOVITE-2M SIDERITE PYRITE ALBITE, ORDERED MICROCLINE, INTERMEDIATE GYPSUM, SYN 32 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13680blk.111 Figure 16: XRD mineralogy Flaxmans Fl-7201 Bulk QUARTZ, SYN KAOLINITE-1A MUSCOVITE-2M PYRITE MICROCLINE, INTERMEDIATE GYPSUM, SYN CLINOCHLORE-1MIIB, FE-RICH ALBITE, ORDERED BERTHIERINE-1M Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13684blk.115 Figure 17: XRD mineralogy Flaxmans

31 Fl-7205 Bulk QUARTZ, SYN KAOLINITE-1A MUSCOVITE-2M PYRITE MICROCLINE, INTERMEDIATE CLINOCHLORE-1MIIB, FE-RICH ALBITE, ORDERED BERTHIERINE-1M 60 Intensity (Counts) X File Name: Theta Angle (deg) c:\...\13685blk.116 Figure 18: XRD mineralogy Flaxmans

32 Graphs of; (A) Injection Pressure vs. Hg Saturation and Incremental Pore Volume, (B) Pore Throat Size vs. Frequency and (C) CO2 Seal Capacity above FWL vs. Water Saturation A) A B) 28

33 C) 29

34 30

35 31

36 32

37 33

38 34

39 35

40 36

41 37

42 38

43 39

44 40

45 41

46 42

47 43

48 44

49 45

50

51