Pore Structure Analysis of Tight Sandstone Using NMR , MIP and Micro‐ CT Methods: A Case Study From the Longdong , Ordos Basin, China

ABSTRACT Pore structure is a key factor of fluid flow within a reservoir. Tight oil has become an increasingly important target in contemporary petroleum exploration and development due to advances in horizontal drilling and hydraulic fracturing technologies. However, tight sandstone reservoirs exhibit poor petrophysical characteristics, strong heterogeneity, complex fluid movement behaviour and poor pore structures. These factors hinder effective reservoir evaluation and oil recovery. Due to their heterogeneous nature, fluids in these nano‐micrometre‐scale pore networks do not follow simple Darcy flow. Thereby complicates the assessment of reservoir quality using traditional methods. We thus examined a multi‐method approach, utilising NMR, MIP and Micro‐CT to comprehensively analyse the pore structure of tight sandstone in the Ordos Basin. The T 2 spectra in NMR were classified into four categories based on their different morphologies, which were mainly single‐peak modes dominated by small pores. The mercury pressure curves were classified into three categories according to their shapes, corresponding to different pore‐throat structures. Micro‐CT shows that amongst them are mainly small pores with low coordination number interconnectivity and complex pore morphology. Finally, we found that the pore structure of tight sandstone has complexity and heterogeneity in different pore scales, and the pore‐throat radius is the key factor that controls the physical properties and pore structure of the study.