Enhanced Reservoir Characterization by Continuous Mineral Composition Logs

Abstract

Reservoir characterization is critical for the exploration and evaluation of oil and gas resources, but also in the context of geological carbon storage. Interbedded baffles play a key role in controlling the CO₂ plume dynamics and geometry and, as a consequence, residual CO₂ trapping capacity can be greatly enhanced due to the presence of baffles. Mineral trapping capacity is also enhanced where CO₂-rich fluids are in contact and react with baffles containing Ca-, Mg-, and Fe-rich silicate minerals leading to the precipitation of carbonates. Importantly, interbedded baffles of a few centimeters are sufficient to affect CO₂ injection and storage conditions as described. In this study, we explore the merit of Hylogger™ data as a complementary approach to traditional reservoir characterisation. The recent development of the Hylogger™ −3 technology with the thermal infrared (TIR) sensor allows the rapid and continuous semiquantitative determination of common minerals in cores and chips from siliciclastic reservoirs at centimeter resolution. As a case study, data from sediment cores from a recent CO₂ storage exploration program in the Darling Basin (New South Wales, Australia) are presented. Hylogger™ data are used in two distinct ways. Firstly, the percentage of mineral groups (framework, carbonate and clay minerals) is calculated based on Hylogger™ data and compared to XRD results on discrete samples. Secondly, the distribution of clay mineral rich intervals is compared to interpreted shales based on wireline log data. We generally found very good agreement between the relative abundance of framework, carbonate and clay minerals when Hylogger™ TIR data were compared to traditional XRD data. The advantage of the Hylogger™ data is it provides a high (centimeter-scale) resolution record of litho-types, while the complementary XRD data can be used to validate the accuracy of the mineral determination by Hylogger™. The comparison of wireline log interpreted shale intervals with clay-mineral rich intervals based on Hylogger™ data mostly showed a good correlation. However, two wireline log shale intervals were found to be composed of almost entirely quartz based on Hylogger™ data. We suspect relatively high gamma ray emissions from very low concentrations of minerals such as K-containing muscovite or kaolinite may have led to the false wireline log interpretation. Spectral gamma ray analysis is currently planned to further explain the observed discrepancy.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015