Relation of Permeability to Water and Volumetric Strain Under Isotropic Cyclic Loading for Terrestrial Oil Sands in China, Xinjiang

Abstract

ABSTRACT The study of transient pulse measurement of core permeability plays a very important role in guiding for field engineers to design reservoir stimulation and development plans. A series of high-temperature and high-pressure triaxial drainage compression tests were conducted on the Karamay oil sands to understand their deformation and flow behavior under multiple stresses, pore pressures, and temperatures. In this paper, the cumulative strain and permeability evolution of Karamay oil sands under shear and isotropic compression are studied experimentally. In this experiment, both vertical and horizontal cores were used to study the anisotropy of the upper compression parameters of the oil sands in two different directions. Through the triaxial compression test, the gauge rate of the oil sands upstream and downstream pressure changing with time was observed. The phenomena of shear rate and isotropic compression rate of Karamay oil sands are proved. The permeability and strain parameters of the accumulator at different temperatures were determined according to the test results. The results show that the vertical permeability and horizontal permeability of oil sands at different temperatures change obviously with the cumulative volumetric strain. The horizontal permeability decreases obviously with the cumulative volumetric strain increasing, and the vertical permeability changes complicated with the cumulative volumetric strain increasing. In general, the vertical permeability at different temperatures is unchanged with the volumetric strain. INTRODUCTION Heavy oil reserves account for more than 70% of the world's proven oil reserves, making it one of the most important oil and gas energy sources in the world. Onshore super-heavy oil reservoir reserves are abundant in China, and their exploitation has an extremely important strategic position and significance. Heavy oil resources in China exceed 200×108t, distributed in more than 70 oil fields in 12 sedimentary basins. At present, petroleum geological reserves put into commercial development are about 14×108t (Jiang et al., 2020). Permeation is a parameter to measure the allowable fluid passage of rock and is one of the key parameters for reservoir evaluation and development (Lu et al., 2021), Permeability reflects the ability of the porous medium rock to transport fluid. Accurate permeability evaluation can effectively improve the efficiency of oil and gas exploration and development (Zhao et al., 2020). Permeability measurement is very important for the reconstruction and development of super-heavy oil reservoirs because it determines the reconstruction effect and production. At present, there are few permeability tests for continental ultra-heavy oil reservoirs in Xinjiang, and the test methods are not uniform. Many people's test results differ greatly. Therefore, we need to conduct a permeability test by transient pulse method for continental ultra-heavy oil reservoirs in Xinjiang to guide field engineers.