Tight sandstone, with severe diagenesis and complex pore structure, differs greatly from conventional sandstone in terms of rock electrical parameters. In subsurface rock electrical experiments, various electrical parameters are confounded and can only be analyzed qualitatively. The lack of quantitative analysis for each individual electrical parameter presents a challenge for the evaluation of oil and gas saturation in tight sandstone. Based on the 2D pore‐throat model and the features of pore structure in the tight sandstone of the Penglaizhen and Shaximiao Formations in the upper and middle Jurassic of the Western Sichuan Depression, this paper presents 3D micro pore‐throat models for three types of tight sandstone. It proposes a finite element‐based rock electrical simulation method to analyze the influence of pore structure parameters, such as throat radius and throat tortuosity, on electrical parameters such as resistivity, formation factor, and cementation index quantitatively. The research revealed the following results: (1) Throats of tight sandstone usually have lamellar or curved lamellar shapes that are slender and narrow. The lamellar throat used in the proposed pore‐throat model is more consistent with the features of tight sandstone than the tubular throat used in the original model. (2) The throat determines the conductivity of tight sandstone. The throat parallel to the electric potential has the greatest influence on conductivity, and the throat perpendicular to the potential has the least influence. (3) In tight sandstone grades I to III, as the porosity decreases, the formation factor increases and the cementation index decreases. (4) The results of the rock electrical simulation are consistent with the results of the rock electrical experiment, which indicates that the proposed rock electrical simulation method of tight sandstone is effective and accurate.

The characteristics of pore-scale two-phase flow are of significance to the effective development of oil and gas resources, and visualization has gradually become one of the hot spots in the research of pore-scale two-phase flow. Based on the pore structure of rock, this research proposed a microscopic glass etching displacement experiment and a Navier–Stokes equation based finite element simulation to study the pore-scale gas–water two-phase flow. Then, this research conducted the proposed methods on the type I, type II and type III tight sandstone reservoirs in the Penglaizhen Formation of western Sichuan Basin, China. Results show that the outcomes of both the microscopic glass etching displacement experiment and the finite element simulation are by and large consistent. The water distributed in the large pores is displaced, and the trapped water mainly exists in the area induced by flow around high-permeability pores, perpendicular pores and disconnected ends of pores. The microscopic glass etching displacement experiment is conducive to better observing the phenomenon of a viscous finger-like breakthrough and air jumps in migration flows in narrow throats, while the finite element simulation has the advantages of cost effectiveness, easy operation and strong experimental reproducibility.

Shaly sandstone reservoir is one of the most significant targets in petroleum and gas exploration. However, the influences of various factors on the resistivity of irregular laminated shaly sandstone are yet to be determined, and it is extremely challenging to accurately calculate the water saturation. By considering shaly sandstone in Zhujiang Formation of Neogene in Pearl River Mouth Basin as an example, this research extracts the shale distribution form and the pore structure by image processing, simulates the resistivity of rock by finite element method, analyzes the influence of shale parameters on resistivity, and deduces the water saturation equation of shaly sandstone. Results show that, in shaly sandstone, shale distributes in irregular laminated patterns on a millimeter scale. The other clean sandstone areas have high porosity and the capacity to reserve oil and gas. At high water saturation states, the shaly sandstone mainly conducts electricity in the clean sandstone area and various shale parameters have minor influences on the resistivity of shaly sandstone. At low water saturation states, the shaly sandstone mainly conducts electricity in the shale area, the resistivity of shaly sandstone is very close to the resistivity of the water layer, and the reservoir is the so-called low resistivity reservoir. The conductive form of clean sandstone area and shale laminae tends to parallel but remains a noticeable difference from total parallel. The simulation results deduced that the water saturation equation of shaly sandstone is more accurate than other equations, which provides an innovative mindset to calculate the water saturation of shaly sandstone.