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| Survey of Shallow Layer Natural Gas in Chengdu-Guiyang Railway of South Sichuan and Southwest Sichuan
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| YUE Zhi-qin1, DING Hao-jiang1, SU Pei-dong2, SUN yi1 |
1. China Railway Eryuan Engineering Group Co. Ltd, Chengdu, Sichuan 610031, China；2. Southwest Petroleum University, Chengdu, Sichuan 610500, China
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Abstract Abstract：Research purposes：Chengdu-Guiyang railway is crossing through multiple oil and gas fields and structures in the red-rock region in Leshan and Yibin. The safety of operation and construction of railway tunnel and deep foundation pit are seriously affected by the shallow natural gas. The purpose of survey is to find out the basic rules of extraction, storage and migration of natural gas, and to provide basis for the railway engineering settings.
Research conclusions：(1)Chengdu-Guiyang Railway is located in the natural gas fields of south Sichuan and southwest Sichuan, 9～11 oil and gas reservoirs in total are found in Triassic, Permian and Sinian strata, the depth of industrial valued gas is about 806～2 358 m. (2)Oil and gas are stored in the crack and pore of strata, the top covering are impregnated by the vertical-migrated gas. It makes the sandstone and mudstone of shallow red rock containing natural gas, and the gas content is positively correlated with the vertical depth, some deep crack can be the pipe for gas-overflowing. (3) The depth of gas weathering crust is 70 m. (4) By the estimation of maximum volume of shallow gas-overflowing in unit time, 3 tunnels are judged as gas tunnel, 22 tunnels as low gas tunnel. (5) Bridge and subgrade can be chosen as preferred engineering form in route selection. The tunnel should take shallow buried and short tunnel group form, the core 〖JP2〗of gas field should be bypassed, and the railway should go through small hills and alongside-〖JP〗mountain sections. (6) The results of this survey can be used for the survey and construction of route, underground engineering, deep foundation (wells) in natural gas region.
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