Informatics Publishing Limited

Tongtao Wang ¹, Chunhe Yang ¹, Xiangzhen Yan ², Hongling Ma ¹, Xilin Shi ¹, J. J. K. Daemen ³

Affiliations
1 State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, Hubei, CN
2 College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266555, CN
3 Mackay School of Earth Sciences and Engineering, University of Nevada, Reno 89557, Nevada, US

Abstract

An equivalent permeability model (EPM) is presented to calculate the equivalent permeability of non-salt layers, which makes the sealing evaluation of bedded salt cavern natural gas storage by numerical simulation easy and sufficient. In the numerical simulations, the effects of non-salt layer property parameters, i.e. horizontal permeability, vertical permeability and dip angle on the sealing of bedded salt cavern natural gas storage can be expressed by a single parameter, the equivalent permeability. We have studied the influence of non-salt dip angle, permeability anisotropy, permeability, buried depth, gas pressure, etc. on the time that it takes for the natural gas to migrate to the ground surface through the non-salt layer formation. The examples show that the EPM is precise and correct, and can meet the actual engineering demands, which includes fewer parameters, and it is implemented easily in numerical simulations. The time needed for natural gas to migrate to the surface is proportional to the increase in anisotropy of permeability and buried depth, but inversely proportional to the increase of non-salt layer dip angle, permeability and internal pressure. The permeability and the dip angle of non-salt layers are the key factors to be considered when analysing the sealing of bedded salt cavern natural gas storage.

Keywords

Numerical Simulation, Permeability Anisotropy, Salt Cavern, Sealing.

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Feng Xu ¹, Chunhe Yang ¹, Yintong Guo ¹, Tongtao Wang ¹, Lei Wang ¹, Ping Zhang ²

Affiliations
1 State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, Hubei, CN
2 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, CN

Abstract

To understand the effect of confining pressure on the mechanical properties of thermally treated coarse sandstone, uniaxial and triaxial compression tests were conducted for six groups of thermally treated sandstone from Xujiahe Formation in southwestern China under confining pressures of 0-40 MPa. The test results indicate that 600°C is a critical threshold of the thermal damage of sandstone by SEM and mechanical tests. When temperature is below 600°C, few micro cracks are observed by SEM. Peak strength, elastic modulus, cohesion and internal friction angle remain constant or increase with increasing temperature and all these values decrease when temperature is above or equal to 600°C under different confining pressures. Under the uniaxial and low confining pressure (≤ 5 MPa), the failure mode shows single or multiple splitting planes and it is easier to generate complex cracks with increasing temperature. Under high confining pressure (10-40 MPa), the failure mode shows a simple shear plane after treatment at different temperatures, i.e. 25-1000°C. The results may provide guidance for rock engineering design after high temperature exposure.

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