Integrated mineralogical and textural datasets for mudrocks based on automated mineral analysis

PIRRIE, D.; SPALLETTI, L.A.; ROLLINSON, G.K.; MATHEOS, S.D.; VEIGA, G.D.; SCHWARZ, E.; SHAIL, R.K.

Manchester

Congreso; 30th IAS Meeting of Sedimentology; 2013

The mineralogy and texture of mudrocks is significant when trying to understand and predict both the microscale porosity-permeability and also their geomechanical properties. Traditional optical microscopy allows the fabric and textures of mudrocks to be imaged, yet determining the overall mineralogy can be difficult or impossible. Bulk rock mineralogical methods such as X Ray Diffraction can provide quantitative mineralogical data sets but lack any textural context. Furthermore, high resolution manual electron microscopy including both SEM and TEM can provide both texture and mineralogy but typically only small areas can be imaged. An alternative approach is the use of automated mineral analysis systems, many of which are just being launched by their respective manufacturers. Although there is some variation in the technologies available and how mineral analysis is achieved, they are all based around automated SEM-EDS analysis. To test the potential application of automated mineral analysis in evaluating the characteristics of mudrocks, we have measured a suite of mudrocks collected from the Tithonian to Valanginian Vaca Muerta Formation, from the Neuquén Basin, Argentina. The Vaca Muerta Formation is of considerable interest as potentially one of the largest shale gas exploration targets in S America. A suite of twenty samples from outcrop representing a range of facies and thermal maturities were analysed for whole rock geochemistry, optical microscopy, whole rock XRD and automated mineral analysis using QEMSCAN® technology. In this presentation the results from the different analytical approaches will be evaluated.