AAPG Geoscience Technology Workshop

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Application of Quantitative Mineralogical Analysis and Radioisotope Techniques in the Characterization and Dating of Deep Petroleum Systems

Abstract

Increasing global energy demand is a transitional driver for exploration in challenging frontiers targets such as deep, tight and unconventional reservoirs. Due to sampling limitations in these extreme environments, the availability of geoscience data constraints is generally poor, making it difficult to de-risk the petroleum system. Addressing these issues requires innovative techniques that can maximise the information available from distal materials which enable the reconstruction of ancient sedimentary environments, regional geodynamic processes, and thermal maturation histories. In addition to rock samples, migrated liquid and gas samples can also play important roles in determining the history of petroleum formation, migration and charge. To address these challenges, we present a practical workflow integrating a mineralogical and radioisotope characterisation approach with respect to solid and fluid samples. We utilize the Tescan Integrated Mineral Analyser (TIMA) platform for automated quantitative mineralogy studies of source and reservoir rocks. The TIMA integrates a high-resolution field emission scanning electron microscope with four silicon drift energy dispersive spectroscopy detectors, allowing ultra-fast measurements of mineral association, concentration and grain size, as well as element distributions on multiple samples of grain mounts, thin sections or polished sections (Ward et al., 2018). Its capability in micro-scale mineralogical analysis of rock chip samples is not only valuable for lithological characterisation of sedimentary basins, but also in identifying and targeting appropriate minerals for in situ chronostratigraphy and thermal history analysis using laser ablation mass spectrometry techniques (e.g., U-Pb, Rb-Sr, and (U-Th)/He dating of siliciclastic sediments). This multi-technique characterisation workflow permits the investigation of porosity, provenance, diagenesis and thermal history of precious drilling samples in petroliferous basins, with advantages over conventional methods in terms of sample consumption (especially drill core), time cost, safety and spatial resolution. By combining these techniques with Re-Os mass spectrometry of liquid hydrocarbons (Selby and Creaser, 2005; Li et al., 2017), we begin to approach a potential solution of direct dating of hydrocarbon generation in deep and ultra-deep environments.