Key Evaluation Aspects for Economic Development of Continental Shale Oil

A series of exploration and development breakthroughs for continental shale oil have been achieved in recent years in China. However, there are great challenges to the risk resistance capability and sustainable ability of large-scale development. The reformation of cognition and mentality is critical to achieve large-scale economic development. A constructive view is proposed that the goal is to achieve reasonable economic returns with maximized recovery and minimized environmental impacts in the lifecycle of an asset project. Adhering to this idea, it is emphasized that the fluid transfer capability, reservoir stimulation potential and oil recovery enhancement potential of continental shale oil with associated key contents must be systematically evaluated. Some important factors are reviewed and discussed in depth such as fluid heterogeneities, micro wettability, macro molecular retention, meso-to-macro geomechanical characteristics, mechanism of proactive utilization of stress interference, and so on, which had been paid insufficient attentions previously. It is concluded that fluid transfer capability is the basis of sweet-spot evaluation and enhanced oil recovery. The cumulative effect formed by the coupling evolution process of shale oil in geologic time plays a key role at present. The multi-scale mechanical properties of shale with complex fabrics and the dynamic evolution behavior of induced stress field are key factors for reservoir stimulation potential. The effectiveness of an artificial reservoir can be significantly improved through proactive utilization of stress interference. The oil mobility in nano pores is the core of micro displacement efficiency. Unique recovery mechanisms with the artificial reservoir can be promoted and utilized through stereoscopic development. The fundamental evaluation properties can at least include fluid heterogeneity, micro wettability, mesoscopic geomechanics and the effective matrix permeability of stimulated reservoir volume. It is vital to have proper characterization and theoretical models for them. It is suggested that development of innovative lab equipment and approaches, establishment of on-site scientific laboratory for continental shale oil, research of digital and intelligent emulation technology and associated evaluation methods, and construction of multi-scale mapping and modeling technology based on "digital twins".