| Laoshishan Tunnel of Yungui Railway is in the Yiliang County. Yunnan Province. Its total length is8075m, the maximum depth is approximately600m. With the construction at parallel guiding adit PDK717+772. the detected gas concentration exceeded the alert limit. And the backplane was on fire during the evacuation process because of the friction. In order to ensure the safety of the tunnel construction, this paper studied the forming reason, the distribution characteristics, and the project impact assessment of the Laoshishan Tunnel.This paper is based on the existing exploration and development information of oil and gas and the existing survey data, and studied the forming reason, the distribution characteristics, and the reservoirs properties of the Laoshishan Tunnel, and assess the danger level of the construction in the Laoshishan Tunnel.By the research, Laoshishan Tunnel is near the southwest edge of the area of the Dianqiangui Qujing-Luliang oil and gas exploration, which is a favourable oil-gas bearing area. The tunnel passes through multiple sets of oil and gas formation, there are multiple sets of source rocks and reservoirs under the area. Although few parts of the source rocks are directly exposed to the surface, the reservoir performance is poor. It is possible that the zone is rich accumulation of oil and gas. This paper predicated that most of the natural gas came from the bottom of the tunnel. The source of the natural gas is deep-seated natural gas from the Longquan Temple Fault and the cracks provide channels for natural gas overflow. The source of natural gas in the tunnel is from deep Silurian strata. Silurian black shales are source rocks, Sandstone and Limestone are good reservoirs. According to the comprehensive judgment the Laoshishan Tunnel is a high gassy tunnel. And DK717+210～DK717+900is high gassy work area, the other sections are low gassy work area. The amount of natural gas spillage is about22.5×104m3, and the largest spillage per unit time is1.152m3/min. |
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