Numerical Simulation of the Influence of Pore Structure on Resistivity, Formation Factor and Cementation Index in Tight Sandstone

Abstract

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.

Characteristics of Tight Gas Reservoirs in the Xujiahe Formation in the Western Sichuan Depression: A Systematic Review

“…In tight gas reservoirs in the Xujiahe Formation in the Western Sichuan Depression, nanoscale pore throats often take the form of sheets or bent sheets, with their formation primarily linked to compaction during diagenesis [29,36,38,41,49]. Studies comparing pore throat development in the T 3 x 2 and T 3 x 4 sections have suggested that the latter exhibits a greater number of throats, with larger throat radii.…”

Pore-scale gas–water flow in rock: Visualization experiment and simulation

“…The western Sichuan depression entered the foreland basin development stage from the end of the Late Triassic and deposited a thick Triassic-Jurassic-Cretaceous terrigenous clastic strata. A large number of tight gas reservoirs have been found in the Triassic Xujiahe Formation, the Shaximiao Formation and the Penglaizhen Formation in the Jurassic [38]. The study area of this research is the Majing-Shifang-Xinchang contiguous structure and the object of the study is the tight sandstone reservoirs of the Shaximiao Formation and the Penglaizhen Formation in the Jurassic (Figure 5).…”

An Experiment-Based Study of Formation Damage Using a Microetching Model Displacement Method

“…During the drilling fluid cycle, the drilling fluid infiltrates the formation rock through pores, thus blocking the pores in rock (Figure 1b,c) and reducing the permeability of the formation, resulting in a dramatic decline in oil and gas recovery efficiency [5][6][7]. In low-porosity and low-permeability sandstone reservoirs [8][9][10][11][12], the formation damage from drilling fluid is extremely complicated. Therefore, with the gradual advancement of exploration and the development of low-porosity and low-permeability sandstone reservoirs, the study of the microscopic mechanism of formation damage by drilling fluid has received increasing attention in recent years.…”