No abstract

Gas volumes for gas shale reservoirs are generally estimated through a combination of geochemical analysis and complex log interpretation techniques. Here geochemical data including TOC (Total Organic Carbon) and results from pyrolysis-based on core and cuttings are integrated with log derived TOC and other petrophysical outputs to calculate the volume of kerogen (for adsorbed gas), kerogen and clay-free porosity, and best estimates of volume of clay (VCL) and water saturation (Sw ). The samples and logs come from the Cooper basin, Australia, where the Roseneath and Muteree fomarions are currently of interest for shale gas potential. This study developed a framework to assist in the selection of a proper mineralogical model. The framework involved grouping of similar minerals into a single mineral category to make a simple mineralogical model because of shortcomings of the stochastic petrophysical techniques, which cannot solve for more minerals than the input curves (only a handful of logs were available for all the wells). The same mineralogical model was used for other wells in the study area where there was no XRD and core data available.Total Organic Content is the basis for the absorbed gas and provides means to correct the total porosity for kerogen and clay. Hence, TOC was estimated cautiously. The log-derived TOC profiles exhibit the best fit to core data in the Murteree Shale as compare to Roseneath Shale where both the resistivity and the sonic logs depict the best overlay. When a proper core calibrated mineral model is chosen that fits well with the XRD mineral proportions, then the porosity fits well with the core derived porosity. After achieving a good correlation between the log-derived mineral constituents and XRD mineral constituents, the user only requires additional conductivity estimates from the Waxman and Smits techniques to solve for gas volume in a gas shale reservoir. The input parameters of the wells having a full log and core data were noted and used consistently in the other wells from the Cooper Basin, which had often either only short core sections available or core data missing. Murteree Shale exhibits excellent potential in and around Nappameri, Patchawarra and Tenappera Troughs but the poor potential in Allunga trough, where Roseneath Shale shows moderate potential in these troughs. The petrophysical interpretation shows that Murteree Shale has the potential to produce commercial quantities of hydrocarbon economically because of significant volume of kerogen (for adsorbed gas), good porosity, significant amount of brittle minerals and producible hydrocarbon.

Brittleness and plasticity indices in hydrocarbon reservoirs are calculated to understand how rocks behave under stress, and for assessing the fracturing performance of clay-rich shale reservoirs and assessing borehole stability. Evaluating shale plasticity/brittleness requires careful analysis of clay mineral composition in target shales and the development of fracking strategies for optimal shale stimulation. Here we report on the mineralogical variability of two Permian lacustrine shale units, the Roseneath and Murteree shales in the Cooper Basin, Australia, that are considered to have potential as unconventional hydrocarbon producers. The study involved a combination of X-ray diffraction, scanning electron microscopy and petrophysical modelling of the Roseneath and Murteree shales in order to obtain a better understanding of the compositions and microfabrics of these two units. This is part of a larger investigation of the shale gas potential of these two units in the Cooper Basin, and the results presented here may ultimately lead to improved reservoir stimulation techniques in both units. Core data has been integrated with wireline logging data to better identify brittle and plastic zones within the Roseneath and Murteree shales. Mineralogical analysis shows that both units are composed mainly of detrital quartz and clay/mica minerals with siderite cement. The clay mineral composition is dominated by illite/mica, and kaolinite in both units. However, based on the relative mineralogical differences between the two units, the Murteree Shale has more favourable brittle properties than the Roseneath Shale, and is considered to be more amenable to hydraulic fracturing for

Changes made as a result of publishing processes such as copy-editing, formatting and page numbers may not be reflected in this version. For the definitive version of this publication, please refer to the published source. You are advised to consult the publisher's version if you wish to cite this paper.

This study investigates petrophysical characteristics of lacustrine Permian Murteree and Roseneath shales in relation to reservoir evaluation of the most prospective gas shale plays in the Cooper Basin, Australia. Both shales were investigated for gas volumes by employing unconventional petrophysical techniques through a combination of source rock parameters acquired by geochemical analysis, and integrating the extracted parameters into log interpretation and core studies. Modeling mineralogical composition using wireline logs require the selection of a proper mineral model. In this study, the mineral model was built in the Interactive Petrophysics (IP's) Mineral Solver module by integrating all regional sedimentological, petrographic, SEM (Scanning electronic microscope), pulse decay and X-ray diffraction data (XRD) from core and chip cutting samples. This study developed a mineral grouping framework to assist in the selection of a proper model to easily solve complex shale gas reservoirs for gas volumes. Furthermore, the permeability of both shales depends on insitu confining stress and permeability of these cores and can be calculated through decay rate of a pressure pulse applied to experimental data. Subsequent to the integrated study as explained above, it is concluded on the basis of extruded parameters (shale porosity, permeability, volume of kerogen, volume of brittle minerals and water saturation) that Murteree formation exhibits better potential than Roseneath formation in and around Nappameri, Patchawarra and Tenappera troughs, while poor potential is exhibited in the Allunga trough. The only location where Roseneath exhibits better potential is in Encounter-01 well.