Pore Structure Characterization of the Tight Reservoir: Systematic Integration of Mercury Injection and Nuclear Magnetic Resonance

Pore structure is the most important factor affecting reservoir quality and petrophysical property of tight reservoir. The effective characterization of pore structures, including pore radius distribution (PRD), throat radius distribution (TRD), pore-throat radius distribution (PTRD), relevant pore structure parameters, etc., is of great importance for the oil exploration and exploitation. Taking the tight sandy conglomerate reservoir as research target of tight reservoir, this paper characterizes the pore structures by a combination of experiments on parallel core samples. These experiments include high-pressure mercury injection (HPMI), constant-rate mercury injection (CRMI), nuclear magnetic resonance (NMR), as well as microscopic analysis of casting thin sections and scanning electron microscopy (SEM). This paper systematically analyzes the advantages and shortcomings of these commonly used experimental techniques. And then, novel methods are proposed to characterize the pore structure (especially the full-range PRD, TRD, and PTRD) by utilizing the advantages of these techniques. In addition, an advanced pore classification scheme is proposed to reclassify the pore types. Finally, the controls of the pore structure on the flow characteristics are investigated, which in turn further demonstrates the correctness and importance of the proposed novel methods for characterizing pore structures. In summary, this study proposes novel methods to characterize the pore structure by integration of HPMI, CRMI, and NMR and provides insights into the pore structure characteristics of the tight sandy conglomerate reservoir.