Key parameters and evaluation methods for large-scale production of lacustrine shale oil

Abstract

Based on the analysis of typical lacustrine shale oil zones in China and their geological characteristics, this study elucidates the fundamental differences between the enrichment patterns of shale oil sweet spots and conventional oil and gas. The key parameters and evaluation methods for assessing the large-scale production potential of lacustrine shale oil are proposed. The results show that shale oil is a petroleum resource that exists in organic-rich shale formations, in other words, it is preserved in its source bed, following a different process of generation–accumulation–enrichment from conventional oil and gas. Thus, the concept of “reservoir” seems to be inapplicable to shale oil. In China, lacustrine shale oil is distributed widely, but the geological characteristics and sweet spots enrichment patterns of shale oil vary significantly in lacustrine basins where the water environment and the tectonic evolution and diagenetic transformation frameworks are distinct. The core of the evaluation of lacustrine shale oil is “sweet spot volume”. The key factors for evaluating the large-scale production of continental shale oil are the oil storage capacity, oil-bearing capacity and oil producing capacity. The key parameters for evaluating these capacities are total porosity, oil content, and free oil content, respectively. It is recommended to determine the total porosity of shale by combining helium porosity measurement with nuclear magnetic resonance (NMR) method, the oil content of key layers by using organic solvent extraction, NMR method and high pressure mercury intrusion methods, and the free oil content by using NMR fluid distribution secondary spectral stripping decomposition and logging. The research results contribute supplemental insights on continental shale oil deliverability in China, and provide a scientific basis for the rapid exploration and large-scale production of lacustrine shale oil.