PROJECT PROPOSAL SHARC2

Transcription

1 PROJECT PROPOSAL SHARC2 Resource Characterisation and Reservoir Performance of Gas Shales Proposed Plan for a Joint Industry Project Commercial-in-confidence

2 Executive Summary CSIRO, in collaboration with Nagra (the Swiss radioactive waste disposal cooperative), Ecole Polytechnique Federal de Lausanne (EPFL), Zurich University of Applied Sciences (ZHAW) and Curtin University, has developed a proposal for investigating the links between geomechanics, rock physics, petrophysics and microstructure in gas shales. The research programme will take a micro-to-macro, experiment-to-theory, lab-to-field approach to evaluate gas storage, gas flow, reservoir properties and performance. The project will involve a systematic experimental characterisation of the impact of partial saturation and organic matter on rock properties and their anisotropy. The experimental results will then be used to inform rock physics, petrophysics and reservoir models in order to improve scientific understanding and aid decision making for shale gas plays. The programme comprises three major parts: 1. Organic matter characterisation, where maceral composition and thermal maturity will be assessed. In addition, microfabrics will be investigated from the centimetre to nanometre scale in order to determine maceral-mineral relationships and maceral-porosity relationships. These results will be linked to potential reservoir performance through integration with measurements mentioned below. The outputs of this program are full characterisation of the nature, porosity and thermal maturity of the organic matter as well as relationships between porosity and maceral type/thermal maturity, leading towards evaluation of potential sites for gas storage and flow paths. 2. Fundamental rock characterisation, including the full CSIRO shale evaluation workflow, plus incorporation of downhole log data where available. The laboratory core plug workflow involves CT scanning, low and high field nuclear magnetic resonance, permeability testing, electrical properties from millihertz to gigahertz plus rock mechanics and chemo-mechanics testing with rock physics and /or microseismic measurements to high pressures and temperatures (up to 100 MPa and 200 C). These tests will be performed across a range of gas saturations to systematically evaluate the impact of gas saturation on rock properties. In addition, offcuts from core plugs are characterised in terms of composition (from XRD, FTIR, neutron capture spectroscopy) and physical properties (permeability, cation exchange capacity, specific surface area, porosimetry, dielectric analysis of pastes, microfabric analysis by optical microscopy, scanning and transmission electron microscopy and focused ion beam nanotomography). Downhole logs will be integrated with core petrophysics and rock physics measurements. Example outputs include: a. systematic evaluation of the impact of saturation on rock properties in gas shales. b. empirical relationships between rock properties, organic matter, saturation and strength. c. rock physics models predicting saturation and elastic properties. d. calibrated petrophysical wireline log workflows for enhanced gas shale evaluation.

3 CONFIDENTIAL RESEARCH PROPOSAL 3. Reservoir performance, where experimental determination of the impact of nonadsorbing (helium) and sorbing (methane) gases on permeability, flow properties physical properties and geomechanical properties will be combined with reservoir simulation in order to improve understanding of the mechanisms of gas migration in shales and to test improved descriptions of matrix-fracture gas transfer and the role these play in production behaviour. Example outputs include quantification of free and adsorbed gas storage properties including methane isotherms, determining the role of organic matter in gas storage and flow and characterising matrix-fracture gas transfer during pressure drawdown. The research program offers a number of benefits to sponsors: Identifying the most effective methods for characterising prospectivity, including downhole tools, and determining whether these techniques are adequate to accurately predict the behaviour and extractability of gas shales in situ. For example, the wide variety of compositions of gas shales may lead to different wireline logging tools being more appropriate for specific plays (e.g. clay-bearing as opposed to carbonate or siliceous). Adding value to core and log data (and seismic if available) from specific fields where a large financial commitment has been made on acquisition but interpretation is difficult due to lack of comparative laboratory data taken under controlled conditions. Improved understanding of micro- and nano-scale porosity which are crucial to the determination of gas storage sites, OGIP calculations, identifying gas flow regimes and ultimately the stimulation design. Development of fit-for-purpose models which could aid in interpretation of future wells in the same field or wells in plays of similar style, elsewhere. Improved rock property determinations from core and seismic data; although partial saturation is known to significantly impact on rock properties, good constraint of its role is currently lacking. Information to assist in the selection of appropriate compositions for reservoir stimulation fluids. The proposed research offers a systematic investigation into gas shale properties from a highly multi-disciplinary research agency with partner institutions specialising in specific relevant aspects of gas shales. Our capability in terms of both world class laboratories and experienced researchers is not available elsewhere, such that the R&D program allows unique and highly novel approaches to gas shale characterisation. The track record of the partner organisations in unconventional gas, shale properties, partially saturated media, micro- to nano-fabric analysis and low frequency measurements is unrivalled and will ensure considerable value-add for the sponsoring companies. [CSIRO Shale Gas Research Proposal March 2012] Page 3

4 1. PROJECT OVERVIEW AND MOTIVATION Shale gas has in recent years moved from a niche area to core business for many major oil and gas producers and has driven the emergence and growth of many smaller players in an expanding marketplace. Major successes in North America have spurred worldwide interest in gas shales, not least in Australia. However, many aspects of resource characterisation and productivity for shale gas plays remain poorly understood, meaning that further research is required to unlock this valuable resource. The CSIRO has extensive experience and a proven track record in the assessment and characterisation of conventional and unconventional hydrocarbon resources and for many years has been at the forefront of both shale and coal research. CSIRO Earth Science and Resource Engineering (CESRE) has been extensively involved in coal seam gas reservoir characterisation and production modelling underpinned by detailed laboratory investigations of gas storage and transport in coal. CESRE has built up a unique broad expertise in shale analysis over many years, culminating in the launch of the CSIRO Shale Research Centre and the development of the current seven member Shale Research Centre (SHARC) consortium. Bringing these elements together to focus effort specifically on gas shales is therefore an obvious and timely next step. The current SHARC consortium involves collaboration with Nagra (the Swiss radioactive waste disposal co-operative), ZHAW (Zurich University of Applied Sciences) and EPFL (the Ecole Polytechnique Federal de Lausanne), who have significant expertise in shale permeability, thermoporomechanics and partial saturation, as well as microfabric evaluation, visualisation and quantification. We intend to continue this collaboration in SHARC2 due to their highly relevant expertise. The SHARC2 project involves integration of CSIRO s specialist capabilities for rock and organic matter characterisation, resource evaluation and reservoir performance modelling as applied to gas shale occurrences across exploration, development and production phases. It builds directly on the track record of the current SHARC consortium and uses the same business model of a Joint Industry Project. The high level goal of SHARC2 is to improve understanding of gas distribution, rock properties and production potential. This will be achieved through targeted research leveraging CSIRO s specialist knowledge and unique facilities, focusing on: 1. Organic composition/distribution and gas storage properties, including the development of laboratory methods that can more rapidly and accurately generate this information benchmarked against standard procedures. 2. Fundamental physical and petrophysical rock properties and how these are related to microstructure, the type and distribution of organic matter and the degree of gas saturation. 3. Systematic understanding of rock mechanics and rock physics of shales as a function of organic matter type, content and gas saturation. 4. Water-rock-gas interactions and experimental methods to monitor the impact of gas adsorption on mechanical properties. 5. Capturing the details of physical and chemical processes operating at nano- to macro-scales in shale gas reservoirs and their accurate representation in thermodynamically consistent production models running with the appropriate level of coupling.

5 CONFIDENTIAL RESEARCH PROPOSAL The proposed 3-year work plan depends in part on materials and data supplied by sponsors to build up elements of an overall characterisation workflow. The experimental workflow will be combined rock physics, petrophysics and reservoir simulation models to better predict reservoir properties and performance. 2. PROPOSED RESEARCH 2.1 Organic Petrology, Mineralogy and Microstructure The microstructure of gas shales is critical to the understanding of a number of basic issues relating to gas residence and rock properties. There are significant unresolved questions on the location of gas in gas shales and these are related to the amount, type and location of porosity in these rocks. For example, a major issue is whether gas is mainly sorbed on and/or in organic matter and associated porosity or if it is distributed throughout the reservoir porosity adsorbed on mineral surfaces and as free gas in inter- and intra-mineral porosity. Clay-bearing gas shales are likely to have pore sizes in the micron to nanometre range and pores in organic matter are of a similar size range, although mainly towards the nanometre end. Figure 1. Bitumen associated with carbonate porosity in Posidonia Shale. Mean random vitrinite reflectance of 0.77%. Reflected white light illumination, oil immersion. Horizontal axis of image = 0.2 mm. [CSIRO Shale Gas Research Proposal March 2012] Page 5

6 Organic petrological analysis using reflected white light and fluorescence mode illumination (e.g. Figure 1) will be carried out to yield information on maceral composition and thermal maturity, which will lead to an understanding of the influence of these properties on gas contents, gas storage and flow properties. Interpretations of organic facies/depositional environment and mineral-maceral relationships will be integrated with other experimental findings mentioned below. The results will be compared to those of other gas shales from the literature to evaluate potential relationships and analogues. Ideally, the samples analysed will include gas immature as well as gas mature shales in order to investigate changes with thermal maturity that may provide insights into gas shale reservoir behaviour. Fabric analysis from millimetre to nanometre scale will be carried out using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and focused ion beam nanotomography (FIB-nt). Such methods will allow us to augment facies interpretations at the millimetre scale, while also investigating pore structure in organic matter and between minerals. The porosity evaluations will lead to a better understanding of any relationships with maceral type and thermal maturity. Furthermore, such porosity evaluations can be compared with those derived from other techniques outlined below (e.g. drying, mercury porosimetry, nitrogen adsorption, image quantification). Some of this work will be performed by CSIRO and some through collaboration with Nagra and ZHAW. Standard mineralogical characterisation will be carried out using x-ray diffraction for composition of the bulk rock as well as smaller grain size fractions. In some cases this will also be supplemented by mineral determinations using FTIR techniques and neutron capture spectroscopy. In addition, other physicochemical properties that are crucial to understanding rock behaviour, such as cation exchange capacity (CEC) and specific surface area (SSA), will be determined. Much of the standard characterisation done in this module will be integrated throughout the rest of the research programme outlined below in order to understand the impact of organic matter and minerals on petrophysical response, geomechanical properties and rock physics behaviour as well as on reservoir simulations. Deliverables: Characterisation of organic matter and mineralogy in appropriate shale suites either provided by sponsors (priority) or acquired by CSIRO, or both. Microfabric characterisation of gas shales and relationship to other rock properties and anisotropy. Evaluation of pore structure and connectivity in organic matter and relationship to thermal maturity and maceral composition. Relationships between organic matter type, total rock porosity, individual porosity elements, gas potential, gas storage sites and implications for gas flow.

7 CONFIDENTIAL RESEARCH PROPOSAL 2.2 Petrophysics, Core, Cuttings and Logs CSIRO has developed a workflow (Figure 2) for characterising shales starting with whole preserved cores and we will adapt this process for handling partially saturated shales and integrate with cuttings analysis. The objectives are to calibrate core to cuttings to log, to integrate mineralogy and geochemistry with petrophysical measurements, cross correlate static and dynamic elastic and mechanical properties in the lab with petrophysical measurements and to provide input to rock physics models. X-ray imaging The petrophysical workflow will involve evaluation of whole cores and core plugs using x-ray CT scanning in order to maximise preservation, orient core plugs and evaluate centimetre to millimetre scale structures present. CSIRO has a conventional medical x- ray CT scanner and it is anticipated that we will have available a latest generation 64- slice scanner for forthcoming projects. Both 2D and 3D images of full core sections in their liners and extracted plugs can be acquired very rapidly at a resolution of about 0.3 mm. These data can be used to assess for example, the presence and impact of bioturbation on rock properties and the orientation of laminations, microfractures and other features which impact on the development of anisotropy (in strength, permeability, velocity, resistivity). Once data has been collected on plugs, further nondestructive imaging will be performed with a new state-of-the art micro-ct scanner which enables an entire core plug to be surveyed at ~10 micron resolution; in addition, regions of interest or oriented sub-samples can be scanned down to a voxel size of about 0.6 microns. Figure 2. CSIRO workflow for characterising shale properties and microfabric. [CSIRO Shale Gas Research Proposal March 2012] Page 7

8 Permeability Testing The establishment of protocols and workflows for accurate and repeatable measurements of gas permeability in gas shale reservoirs is critical. Currently many different methods are used, some of which are inappropriate in terms of technique and others which are inappropriate due to the processes applied to the sample before testing (e.g. drying, crushing). Working in collaboration with Nagra, who have vast expertise in gas permeability testing of shales, we aim to develop appropriate fit-forpurpose techniques and testing protocols that provide reliable and repeatable results on gas shales. Anisotropy of permeability related to microfabric and sedimentary structures will be evaluated, as will relationships between diffusivity, surface chemistry, wetting state, permeability and gas trapping. Dielectric Characterisation The impacts of saturation, water content, stress and organic matter on resistivity and dielectric constants for gas shales will be evaluated experimentally using CSIRO s specialised in-house systems. These will help us to understand the fundamentals of gas shale properties as well as enabling the log-to-lab correlation various types of resistivity and dielectric tools, including the latest generation of multi-frequency devices. Our existing systems enable us to measure a wide range of frequencies and incorporate a range of sample sizes, types and formats (plugs and discs) as well as specialised cells for determining anisotropy of electric properties (cubes). We also integrate measurements on dry and hydrated powders and pastes made from cuttings and standard minerals. Dielectric measurements between 100 khz and 3 GHz will be made using systems designed in-house. This frequency range covers the range of all dielectric logs and also induction- or propagation-type resistivity logs that can be influenced by dielectric effects. Both dielectric constants and conductivities derived from the measurements are strongly frequency dependent, with water content governing the dielectric response at the highest frequencies and various surface charge effects increasing the dielectric constant as frequency decreases. Such surface charge effects are related to the cation exchange capacity (CEC) and specific surface area (SSA) of the minerals present within the rock and are generally dominated by the effects of clays. Given this known behaviour, dielectric properties of rocks can thus be used to evaluate water content independently of mineralogy at high frequencies, whereas the dispersion at lower frequencies can be used to evaluate CEC and indirectly estimate mineralogy in terms of clay fraction and activity of the clays. This enables us to measure water saturation in and estimate rock strength of preserved clay-bearing gas shales and as the latter commonly depends on the amount and types of clays, their hydration state and rock porosity. Our research over the past years has clarified many of these relationships for saturated, lean shales. However, the role of organic matter on dielectric response is very poorly understood. Whereas most organic matter is electrically inert, it may be associated with pyrite that exhibits strong induced polarization, or it may affect clay surface electrochemistry and hence electrical activity. By combining the organic matter analyses with the dielectric analyses, we intend to evaluate the role of organic matter on dielectric constants and conductivities. Dielectric measurements can also be evaluated for powders or pastes derived from cuttings and therefore can also be used

9 CONFIDENTIAL RESEARCH PROPOSAL to develop a dielectric log for comparison with downhole log response. Finally, dielectric analyses of synthetic samples comprising mixtures of clay/carbonate/silica and organic matter extracted from gas shales will be performed to further assess the role of organic matter on dielectric response. Low Frequency Electrical Properties CSIRO s in-house impedance measurement systems give us the capability to investigate the entire frequency range between milli-hz and MHz, where diffusive and surface-controlled low frequency polarisation mechanisms are manifest. Resistivity measurements will be made on preserved plugs with a 4 electrode cell in the form of an impedance spectrum from <1 Hz to 100 khz corresponding to all types of galvanic and induction logs. Impedance spectroscopy captures resistivity dispersion caused by low frequency electrical polarisation mechanisms that can be diagnostic of clay mineral chemical sensitivity. In conventional reservoirs, resistivity is the main method used to assess hydrocarbon saturation. In some gas shale reservoirs, a modified shaly sand approach for saturation estimation appears to work, whereas in others, electrically-based estimates of saturation correspond poorly to independent measurements of gas content. Therefore, more research at a fundamental level is needed to illuminate the roles of surface charge distributions and tortuosity of the capillary bound brine in controlling conductivity and to clarify the effects that organic matter has on low frequency electrical behaviour. One approach to investigating partial saturation will be the use of various salt solutions under different relative humidity atmospheres to induce dehydration to specific partial saturations so that a large range of saturations can be investigated systematically, ideally between fully water saturated and about 20% water saturated (close to maximum gas saturations observed in situ). We know from previous studies that the interactions of oil with clay minerals are complex and lead to unusual electrical behaviour. Oils may be bound onto clay surfaces and deactivate them electrically, reducing conduction and polarisation, or can increase conductivity at low water contents by restricting the amount of water on surfaces and enabling the brine to concentrate in pore pathways. The hydrophobicity of certain mineral surfaces leads to the water forming droplets that have a characteristic dielectric response. Our experiments will ascertain whether the various types of organic matter behave in the same way as oils or are simply inert and can be counted as non-conducting matrix. Low and High Field Nuclear Magnetic Resonance In gas shales, the main objective of NMR logging is for detecting gas and water contents independent of matrix mineralogy. The large range of NMR techniques we have available in the lab can be employed to better interpret conventional data and to develop entirely new models of fluid-rock interaction. CSIRO has a Maran 2 MHz spectrometer with gradient coil system that enables the non-destructive measurement of the distribution of water in pores of varying size down to nanometre scale and also to evaluate the response of different fluids in the pores. This low field system can also be used to measure local diffusivity and anisotropy of diffusivity using magnetic gradient [CSIRO Shale Gas Research Proposal March 2012] Page 9

10 methods. A high pressure (5000 psi) elevated temperature (80 C) core holder system enables the measurement of properties nearer to in-situ conditions with elevated gas and water pressures. The Maran system is complimented by two Bruker Minispec instruments that operate at 10 MHz (homogeneous field) and 16 MHz (with permanent gradients similar to pad-type downhole NMR tools). The former is especially useful for detecting bound water/liquid hydrocarbons that have very short relaxation times; the response for short times can be further improved by using SOLID echo methods. The latter helps to understand fluid distributions using diffusion editing techniques and can operate on very small samples such as extracts of organic rich concentrates or fractions of experimental columns. CSIRO also has a suite of advanced high field NMR instruments which can be used for both solution and solid state NMR experiments, using probes tuned to 13 C, 23 Na 29 Si and 27 Al as well as the protons discernible at low field. Solid state 13 C NMR can be used for organic matter typing; for example, it can distinguish between aromatic and aliphatic bonding in macerals and oils. Using direct or cross-polarisation methods to excite different nuclei and with an almost unlimited range of programmable pulse sequences available, characterisation procedures can be custom designed to detect and quantify the dynamics of hydration/dehydration and adsorption/desorption to gases. Even the solid rock matrix can be studied with probes tuned to aluminium and silicon nuclei, whereas the fluids change mobility, relaxation time and chemical shift according to binding strength and the thickness of adsorbed layers. For example, CSIRO has previously determined a relationship between proton chemical shift anisotropy of bound water and the wettability of that mineral surface to crude oil. Wettability is crucial to how gas resides and migrates in shales and may well be important in terms of loss of fluids to the reservoir formations during the hydraulic fracturing processes (see Geomechanics section below). Neutron Petrophysics Arguably one of the most important of the petrophysical technologies is that related to neutrons. Neutrons respond to both fluids and solids in complex ways and can also penetrate steel casing, making them especially attractive for shale gas applications if the range of open hole logs is limited. There are three main types of neutron petrophysics applied downhole: 1. Neutron porosity is fundamental in combination with density porosity to compute pore space and clay content. Methods for neutron porosity measurement have recently become more sophisticated incorporating thermal and epithermal energies and near and far detector arrays. This leads to improvements in accuracy of the measurement when the tool physics and data corrections are properly understood. 2. Pulsed neutron capture spectroscopy from a high energy downhole source can directly detect light elements other than hydrogen, especially C, O and Cl. 3. Pulsed neutron capture spectroscopy methods optimised for elements such as Si, Ca, Mg, Fe can be used to constrain the mineral content of a formation.

11 CONFIDENTIAL RESEARCH PROPOSAL As gamma ray emission spectra of different elements overlap and neutrons and photons can be scattered and adsorbed by minerals and fluids in formations, making quantitative measurements is challenging. Therefore physical understanding at a fundamental level, modelling and laboratory calibration are all needed. CSIRO is one of the few research organisations to have a dedicated neutron petrophysics team. As well as having wide expertise and experience in theory and computational methods for neutron physics, the team has built an experimental facility complete with a programmable pulsed neutron generation and detection system. The proposed research plan will therefore combine analyses of existing log data from sponsors with theory, tool response modelling (forward and inverse) and experiments directed at improving interpretations and understandings of neutron porosity and the elemental determinations and products derived from them. The team has worked on topics of special relevance to shale gas, such as applications to coal and determination of water salinity in situ using calibrated chlorine detection. Even with little environmental correction, the C/O ratio of the formation can indicate potential pay zones behind casing and whether there may be liquids potential. We will also investigate the potential for sophisticated organic matter quantification and typing. Matrix element logs are valuable for detecting and correlating gas sweet spots in shale formations as well as providing the input to form a closed-form matrix mineralogy model vital for determining elastic properties and to compute grain densities needed for mechanical, rock physics and porosity/saturation computations. Our research here will focus on efficient data analyses and calibration against XRD/XRF and infrared determinations of mineralogy made on slabbed core and cuttings using a number of standard and CSIRO in-house methods. A further way neutrons can be used for gas shale petrophysics is small angle scattering (SANS). SANS will be applied to gas shales to establish whether the amount of closed porosity is different under wet and dry conditions for the shale samples to be investigated. The SANS technique also allows identification of pores that water cannot access. If closed porosity is significant in shales, then methane extraction is likely to be limited. The degree of accessibility by methane may vary with moisture content if the shale is highly susceptible to water-swelling and this would affect interpretation of experimental results. It is proposed that SANS analyses are performed on the samples and that the findings are compared to the other analyses of the proposed study, such as XRD, microstructural analysis from SEM and x-ray methods, liquid and gas permeability and NMR-derived fluid diffusivity. Data Integration The laboratory based petrophysical characterisation outlined above is intended to provide a basis for the development and calibration of workflows for downhole log evaluation. Core to log integration would be performed on available logs provided by sponsors, preferably including both standard and special tools. The latter include spectral gamma ray, neutron capture spectroscopy, standard density/neutron logs, NMR logs, electric and dielectric logs and advanced sonic logs (e.g. cross-dipole shear, Stoneley waves and frequency dispersion curves). These logs can be robustly calibrated from laboratory measurements and used to develop enhanced workflows towards evaluation of organic matter content, saturation, mineralogy and rock strength. [CSIRO Shale Gas Research Proposal March 2012] Page 11

12 Deliverables: 2D and 3D CT images of gas shales interpreted to evaluate sedimentary or other millimetre scale visible structures and integrated with interpretations from the other measurements made. High frequency dielectric response in gas shales related to organic matter contents, saturation, mineralogy and rock strength as appropriate. Development of dielectric logs from powders and pastes tied to wireline electrical logs. Determine factors affecting resistivity at low frequency and tie in with downhole logs to develop workflows for assessing saturation in gas shales. Assess validity of Archie-type and shaly sand approaches for gas shales. Calibration of NMR water and gas relaxation signals in shales and integration with diffusivity measurements using low field NMR; investigation of organic matter types, fluid-rock interactions and wetting tendencies using high field NMR. Improved calibration of neutron capture spectroscopy for quantification of matrix mineral assemblages as well as for organic matter quantification and typing. Develop relationships between neutron response, porosity, saturation and pore size in gas shales. Calibrated robust wireline log workflows for characterising properties of gas shales. Gas permeability protocols and workflows to reliably assess gas permeability in low permeability gas shales. Stress dependence and organic matter impact on gas permeability and anisotropy of gas permeability for selected samples. 2.3 Geomechanics and rock physics: roles of mineralogy, microstructure, organic matter and saturation Strength, stiffness (static/dynamic) and their anisotropy for gas shales is important for directional drilling as well as the location and propagation of hydraulic fractures. Gas saturation, which has significant impact on rock strength and both static and dynamic stiffnesses, will vary across a given shale reservoir as a function of the pore size distribution. This parameter can vary over at least three orders of magnitude, normally from micron to nanometre scale. The interlinking of these factors causes considerable complications for calculating static and dynamic rock properties. For example, dynamic stiffness is often assessed in the field from velocity in order to help locate hydraulic fractures, but these methods assume constant saturation and as such may be erroneous. Currently, there are few experimental tests run under controlled conditions to evaluate the impact of partial saturation on strength and stiffness and no models for understanding or predicting the rock physics response of gas shale reservoirs. The role of organic matter on strength, stiffness and permeability in gas shales is currently uncertain. In coal and soft clays, the amount and type of organic matter has a

13 CONFIDENTIAL RESEARCH PROPOSAL significant impact on strength and permeability due to swelling and shrinkage. Understanding the role organic matter plays in determining storage, permeability, strength and anisotropy characteristics in these rocks will be critical for producibility of these reservoirs. In addition, the chemically active nature of clay-bearing gas shales and the degree of partial saturation may also affect pore fluids injected into the system for hydraulic fracturing. In some cases, significant amounts of water have been lost in the subsurface and there is debate as to whether osmotic processes or capillary processes related to partial saturation and wettability have been a factor. In this part of the project, we propose to investigate the issues outlined above. The impact of partial saturation can be investigated systematically by using sponsor-derived samples that have been preserved as close as possible to in situ water contents, evaluating saturations by some of the petrophysical methods outlined above and then using rock mechanical testing techniques to evaluate strength (friction coefficient, cohesion, unconfined compressive strength), stiffness (static/dynamic Poisson s ratio, Young s modulus) and low frequency response in gas shales in relation to saturation. In addition, CSIRO will acquire some preserved shales at close to 100% water content and systematically dehydrate them using specific relative humidity atmospheres to set levels of water saturation and evaluate rock mechanics, rock physics and petrophysical properties. The role of organic matter in anisotropy of velocity and strength properties will also be investigated through triaxial, ultrasonic and low frequency tests. Mechanical properties experiments (oedometric and triaxial) will also be performed by our collaborators Nagra/EPFL on the Opalinus Clay as an analogue as there is already considerable knowledge of the behaviour of this shale under partially saturated conditions. The development and validation of a constitutive model for partially saturated shale mechanical properties would be possible through this collaboration. The low frequency tests will be performed at Curtin University in Perth (who are colocated with CSIRO). Rock physics models will be developed on the basis of both laboratory measurements at low and high frequency and any other available data provided by sponsors (e.g. sonic logs, VSPs, seismic data, microseismics). Attenuation and dispersion of elastic waves are partially caused by wave-induced flow phenomena. This includes the mesoscopic effect of partial saturation but also squirt flow and microscopic boundary layer flow. Numerical tools will be developed to model these effects based on anisotropic differential effective medium modelling. In terms of elastic wave propagation through fractured media, either existing or newly created fractures can dominate flow permeability in gas shales. These fracture networks will change wave propagation properties, not only in the effective medium sense, but also with regard to the amount of elastic scattering. An example would be the propagation of a highfrequency microseismic signal through a newly created fracture network. Our aim is to model these wave propagation effects using time-domain finite element simulations. Hydraulic fracturing operations in gas shales can cause microseismicity. The mapping and tracking of microseismic events in space and in time gives additional insight into the evolution and preferred directionality of flow permeability. Numerical finite element modelling based on both experimental and field microseismic events will give further [CSIRO Shale Gas Research Proposal March 2012] Page 13

14 insight and can assist data interpretation with respect to (a) the coupling of fluid pressure distribution and regional tectonic stress field, and, (b) the stress sensitivity of gas permeability. The impact of fluid chemistry and capillary effects will also be evaluated through both small (4 mm x 4 mm) and core plug scale experimental testing. The cornerstone of the experimental programme will be experimental testing on the small samples to determine chemo-mechanical properties and likely osmotic response to invasion of hydraulic fracturing fluids of different composition to the shale pore fluid. This will be done on fully saturated and partially saturated samples, where deformation is measured in relation to salt-concentration and the osmotic membrane efficiency and chemomechanical coupling parameter (coupling strain to osmotic pressure) is calculated. Capillary imbibition will also be studied on small samples with fluid chemistry similar to that of the in situ fluids. Some experiments will be performed on larger samples to test for any sample size effect, although these samples would be fewer in number due to long time periods required for equilibration. Deliverables: Relationships between saturation, strength and static/dynamic stiffness in gas shales. Impact of organic matter on strength and velocity anisotropy. Rock physics models for gas saturation and organic matter content in gas shales tied to downhole logs where available. Constitutive mechanical model for partially saturated shales. Role of capillary and osmotic forces for fluid injection into gas shales. 2.4 Laboratory Experimental Studies on Gas Storage and Migration Processes in Shales An important question with gas production from shale reservoirs is related to the role that free gas in the porosity and adsorbed gas, predominantly in the shale matrix, play during production. It has been noted previously that adsorbed gas made up approximately 50% of the total gas content for some gas shale samples. The contribution this makes to production is a function of the diffusion behaviour (including effects such as fracture spacing) and permeability of the shale matrix. A common assumption has been that adsorbed gas makes little contribution to production and that free gas in the shale porosity is the main source. This is based on reservoir simulation where the very low permeability of the shale matrix implies that pressure drawdown and thus gas desorption is limited. However this is being challenged by work which has found that the organic matter in shale can have significant porosity and thus provide a diffusion path for gas migration. In addition, the organic matter typically also comprises the primary gas adsorption capacity. Recently, it was proposed that matrix-fracture

15 CONFIDENTIAL RESEARCH PROPOSAL transfer in some gas shales could be described by a triple porosity model to represent the role of the matrix, the porosity of the organic matter and the fracture network. Thus there is an emerging model for gas storage and migration in shale reservoirs where the organic matter plays a central role. However this conceptual model for shale gas may not encompass all shale reservoirs; most of the emphasis to date has been on the Barnett Shale with little work on other formations worldwide. Given the range of variability present in the characteristics of gas shales their production behaviour is likely to also be highly variable. This research task involves investigations on the nature of gas storage and the mechanisms that determine gas migration in shales, through laboratory experimental studies on core samples. It builds on the organic matter and porosity characterisation work performed in the other tasks mentioned above. The following will be characterised as part of this task: Gas storage: This will involve adsorption measurements on crushed samples combined with measurements on intact core to identify the quantities adsorbed and as free gas. Adsorption behaviour on crushed shale at reservoir temperature with respect to pressure will be measured using CSIRO s volumetric-gravimetric adsorption isotherm rig. Sub-sampling of this crushed material will be used to investigate the relationship between total organic content and adsorption capacity for shale. Gas storage with respect to pressure for intact core samples will be measured in the CSIRO triaxial multi-component gas rig. This equipment is well established through extensive research on gas storage and migration for coal bed methane applications. Gas migration: This will comprise two main activities; gas diffusion experiments on intact core and measurements of matrix and core permeability. Helium and methane are used. The diffusion experiments will involve saturating a core sample with gas and observing the diffusion of gas with time. This data will be used to develop an appropriate modelling description for the gas diffusion process, in particular whether a dual or triple porosity model or some other modelling basis is required. Gas flow through experiments will then be carried out on the gas saturated core samples to measure permeability with respect to effective stress. Shale strain with respect to gas sorption and elastic modulus with respect to effective stress will also be measured. All this information will help develop a gas transport model for shale for non-sorbing and sorbing gases. The impact of gas type on mechanical properties will also be evaluated. Deliverables Characterisation of free and adsorbed gas storage for gas shales. Measurement of methane gas adsorption isotherms and the quantity of free gas. [CSIRO Shale Gas Research Proposal March 2012] Page 15

16 Characterisation of the role of organic matter in gas storage. Impact of gas sorption on mechanical properties. Characterisation of matrix-fracture gas transfer during pressure drawdown. 2.5 Improved simulation of gas production from shale reservoirs There are a number of challenges with the simulation of gas production from shale reservoirs. One relates to the representation of flow within the fracture system, including fractures induced through hydraulic stimulation and those naturally present. Another aspect is the gas transfer into this fracture system from the shale matrix. This task will integrate the characterisation work on shale porosity and the gas migration processes performed in the tasks mentioned above, to focus on reservoir simulations of fracture-matrix transfer. This work will build on experience in modelling fracturematrix transfer in naturally fractured dual porosity adsorbing formations. Deliverables Testing of the accuracy of existing matrix-fracture gas transfer models used in reservoir simulation. Development of improved matrix-fracture gas transfer models for reservoir simulation and the testing of these models using experimental data.

17 CONFIDENTIAL RESEARCH PROPOSAL 3. DELIVERABLES SUMMARY DELIVERABLE 1: Characterisation of organic matter and mineralogy in appropriate shale suites either provided by sponsors (priority) or acquired by CSIRO or both. Microfabric characterisation of gas shales and their relationship to other rock properties and anisotropy. Evaluation of pore structure and connectivity in organic matter and relationships to thermal maturity and maceral type. Relationships between organic matter type, total rock porosity, individual porosity elements and gas storage sites, gas potential and gas flow. DELIVERABLE 2: 2D and 3D CT images of gas shales interpreted to evaluate sedimentary or other millimetre scale visible structures and integrated with interpretations from the other measurements made. High frequency dielectric response in gas shales related to organic matter contents, saturation, mineralogy and rock strength as appropriate. Development of dielectric logs from powders and pastes tied to wireline electrical logs. Determine factors affecting resistivity at low frequency and tie in with downhole logs to develop workflows for assessing saturation in gas shales. Assess validity of Archie-type and shaly sand models for gas shales. Calibration of NMR water and gas relaxation signals in shales and integration with diffusivity measurements using low field NMR. Investigation of organic matter types, fluidrock interactions and wetting tendencies using high field NMR. Determine the relaxation time and diffusivity range of gas and fluids adsorbed on mineral surfaces. Improved calibration of neutron capture spectroscopy for quantification of matrix mineral assemblage and for organic matter quantification and typing. Calibrated robust wireline log workflows for characterising properties of gas shales. Gas permeability protocols and workflows to reliably assess gas permeability in low permeability gas shales. Stress [CSIRO Shale Gas Research Proposal March 2012] Page 17

18 dependence and organic matter impact on gas permeability and anisotropy of gas permeability for selected samples. DELIVERABLE 3: Relationships between saturation, strength and static/ dynamic stiffness in gas shales. Impact of organic matter on strength and velocity anisotropy. Rock physics models for gas saturation and organic matter content in gas shales. Constitutive mechanical model for partially saturated shales. Relationships between water content, methane sorption, mechanical properties and permeability in gas shales. Role of capillary and osmotic forces for fluid injection into gas shales. Incorporation of mechanical and permeability behaviour into appropriate reservoir models. DELIVERABLE 4: Characterisation of free and adsorbed gas storage quantities for gas shales. Measurement of methane gas adsorption isotherm and the quantity of free gas. Characterisation of the role of organic matter in gas storage in gas shales. Characterisation of matrix-fracture gas transfer during pressure drawdown. DELIVERABLE 5: Testing of the accuracy of existing matrix-fracture gas transfer models used in reservoir simulation. Development of improved matrix-fracture gas transfer models for reservoir simulation and the testing of these using experimental data. DELIVERABLE 6: Reporting and Communication CSIRO will provide brief updates on project progress on a bi-monthly basis and will provide a written interim progress report after 6 months Annual REPORT. CSIRO will host an annual conference in Australia and provide an annual report each year with supporting electronic data and database results. CSIRO researchers will visit sponsor companies where

19 CONFIDENTIAL RESEARCH PROPOSAL possible to present on specific parts of the project. 4. KEY PERSONNEL Project Leader: Dr. David Dewhurst (CSIRO) Dave Dewhurst is a geologist and experimental geomechanicist by background and has worked on clays and shale properties for 20 years, investigating strength, compaction, faulting fluid flow and rock physics phenomena. He is head of the CSIRO Shale Research Centre and the leader for the current SHARC JIP. Petrophysicists: Dr. Ben Clennell., Dr. Matthew Josh, Dr. Lionel Esteban (all CSIRO). Ben Clennell has 20 years postdoctoral experience in rock petrophysical properties research, focusing most recently on NMR, electrical and x-ray methods. He was SPWLA Best Paper award winner in 2006 and SEG Honorary Lecturer for the Asia Pacific Region in Matthew has a Ph.D. in borehole dielectric tool development for coal. He is the lead scientist behind the CSIRO dielectrics laboratory and has 5 years postdoctoral experience at CSIRO and ANSTO. Lionel is a geologist with expertise in characterisation of rock physical properties, shales and gas hydrates and has specialised in electrical and NMR petrophysics. NMR Specialist: Dr. Iko Burgar (CSIRO) Iko Burgar runs the CSIRO Nuclear Magnetic Resonance Laboratories in Clayton, Victoria. A physicist by training, he has over 30 years experience in academic and industrial research including many years with BHP. He has worked on a wide range of material and chemical analysis problems, including polymer and interface science, porous media and coal and organic matter analyses. His recent contributions to petrophysics include pioneering work on clay and shale wettability and specialised training courses for oil company staff. Reservoir Engineers: Dr. Luke Connell, Dr. Zhejun Pan (both CSIRO) Dr Luke Connell and Dr Zhejun Pan operate the CSIRO unconventional gas laboratory which specialises in the study of gas storage and migration processes in adsorption dominated, multi-porosity formations. A key part of this work is the integration of laboratory and field experimental work with the development of improved reservoir simulation tools. Rock Physicists: Professor Boris Gurevich (Curtin University/CSIRO), Dr. Marina Pervukhina (CSIRO), Dr. Maxim Lebedev (Curtin University). Dr. Marina Pervukhina is a geophysicist and physicist by background. Her expertise is on theoretical and numerical modelling of elastic, electrical and transport properties of rocks. Professor Boris Gurevich is a theoretical rock physicist by background, with expertise in numerical modelling of wave propagation through anisotropic media. Dr. Maxim Lebedev is a physicist by background. His expertise is on shock wave propagation, fracture mechanics, instrument development and low frequency testing. [CSIRO Shale Gas Research Proposal March 2012] Page 19

20 Experimental Geomechanics and Rock Physics: Dr Claudio Delle Piane, Dr. Joel Sarout (both CSIRO), Dr. Paul Marschall (Nagra), Professor Lyesse Laloui and Dr Alessio Ferrari (both EPFL). Dr. Claudio Delle Piane has expertise in experimental rock mechanics testing, scanning electron microscopy and a strong structural geological background. Joel Sarout works on rock mechanics and rock physics research in rocks and fluids from experimental and theoretical points of view. Dr. Paul Marschall is a geophysicist and hydrogeologist by background. His expertise is on thermo-hydro-mechanical coupled processes and fluid/gas transport in claystone formations. Professor Lyesse Laloui has a strong expertise in the fundamental study of soils and man-made geo-systems with emphasis on the mechanics of various interacting multi-scale and multi-physics phenomena. This includes theoretical and numerical approaches, engineering applications as well as the development of an advanced experimental geomechanical laboratory. Dr. Alessio Ferrari is a senior researcher at the Soil Mechanics Laboratory of the Swiss Federal Institute of Technology in Lausanne. His expertise focuses on the analysis of the thermo-hydro-mechanical behaviour of soils and shales, the development of advanced testing facilities for geo-materials and the assessment of natural hazards. Microstructure and Visualisation: Dr. Lucas Keller (Zurich University of Applied Sciences). Dr. Lukas Keller is a petrologist and structural geologist by background. His expertise is on the 3D pore analysis of clay rocks. He specialises in focused ion beam nanotomography and extraction of quantitative microstructural parameters from images. Organic Petrology: Dr. Neil Sherwood (CSIRO); Dr. Zhongsheng Li Neil Sherwood leads unconventional gas activities in CSIRO and with his team has developed a range of innovative methods for organic matter characterisation including laser micropyrolysis and Fluorescence Alteration of Multiple Macerals (FAMM ). He has about 30 years experience in organic petrological analyses, including coals, petroleum source rocks, oil shales and gas shales. Zhongsheng Li works with the Organic Petrology team and has experience on various aspects of coal/organic matter characterisation including developing techniques for elemental analyses and elemental mapping of coal macerals using electron microprobe techniques, applying micro-ftir analysis to identify functional groups in macerals, using SEM for microstructure analysis, and applying quantitative X-ray diffraction analyses for a range of coal-related materials. 5. BENEFITS AND IMPACTS This research offers a number of benefits to potential sponsors: 1. Identifying the most effective methods for characterising prospectivity, including wire line tools and determining whether these techniques are adequate to accurately predict the behaviour and extractability of gas shales in situ. For example, the wide variety of compositions of gas shales may lead to wireline logging tool choices appropriate for specific plays (e.g. clay-bearing as opposed to carbonate or siliceous).