Abstract
Using salt caverns for an underground strategic petroleum reserve (SPR) is considered as an ideal approach due to the excellent characteristics of low porosity, low permeability, self-healing of damage, and strong plastic deformation ability of rock salt. Salt deposits in China are mostly layered rock salt structures, with the characteristics of many interlayers, bringing great challenges for the construction of SPR facilities. Studying the microscopic pore characteristics of the rock surrounding SPR salt caverns in different environments (with brine and crude oil erosion) is necessary because the essence of mechanical and permeability characteristics is the macroscopic embodiment of the microscopic pore structure. In this paper, XRD tests and SEM tests are carried out to determine the physical properties of storage media and surrounding rock. Gas adsorption tests and mercury intrusion tests are carried out to analyze the microscopic pore structure, specific surface area variation and total aperture distribution characteristics of SPR salt cavern host rock. Results show that: (1) Large numbers of cores in interlayer and caprock may provide favorable channels for the leakage of high-pressure crude oil and brine. (2) The blockage of pores by macromolecular organic matter (colloid and asphaltene) in crude oil will not significantly change the structural characteristics of the rock skeleton, which is beneficial to the long-term operation of the SPR salt cavern. (3) The water–rock interaction will bring obvious changes in the micro-pore structure of rock and increase the leakage risk of the storage medium. The results can provide theoretical bases and methods for the tightness analysis of China’s first underground SPR salt cavern.
Highlights
The dynamic development of the world economy means that the demand for energy is increasing from year to year in virtually all sectors of this economy [1,2]
When the interlayer is eroded by crude oil, compared with the scanning results of electron microscopy and microcracks onon thethe surface of the sample are microscopy under underconventional conventionalconditions, conditions,the thepores pores and microcracks surface of the sample covered by abylayer of medium, which directly confirms the are covered a layer of medium, which directly confirms theassumption assumptionofofthe thepore poreblockage blockage being being caused by macromolecular organic matter in crude oil
(2) Under the condition of crude oil rock, erosion, the changes inrock the specific areabyand size of pores by macromolecular organic matter in crude oil, which will not distribution characteristics of salt rock, interlayer and cap rock samples are caused by the significantly change the structural characteristics of the rock skeleton, which is beneficial to the blockage pores by macromolecular organic matter in crude oil, which long-termofoperation of the strategic petroleum reserve (SPR) salt cavern; notbrine significantly change thein structural characteristics of the rock skeleton, which is beneficial
Summary
The dynamic development of the world economy means that the demand for energy is increasing from year to year in virtually all sectors of this economy [1,2]. With in the stage of demonstration, and the underground salt cavern oil storage is far behind that of some the advancement of the national strategic petroleum reserve plan, the implementation of underground developed countries. The properties of mudstone interlayers in contact with oil or brine are not clear What is more, these properties are the most crucial factor to ensure the SPR salt cavern long-term safe and stable operation, due to the essence of the mechanical and permeability characteristics of the surrounding rock being the macroscopic embodiment of its microscopic pore structure. This will lay a foundation for further study on the macro-mechanical characteristics and porosity and permeability characteristics of surrounding rock of SPR salt cavern of Jintan, as well as a basic reference for similar engineering practices in other places. The process process of crude oil injection–production of SPR in rock salt
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