Assessment of the water-sealed safety of underground crude oil storage based on a three-dimensional refined numerical model
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摘要:
地下水封油库利用"隙存水封"原理实现原油大规模地下储存, 水封安全性是决定地下油库安全经济运行的重要前提。为评价某地下水封油库的水封安全性, 基于精细化工程地质勘察, 获取了洞库围岩、库区内断层带、节理裂隙密集带、破碎带的渗透系数, 综合分析了库址区范围内的渗透系数空间变化规律; 并结合多源高精度勘察信息构建了三维精细化渗流数值模拟模型, 在对比分析三维精细化模型与均匀介质模型的优劣后, 通过数值模拟, 对比分析了有、无水幕条件下洞库的水封可靠性, 并预测了洞库施工和运营期的涌水量。结果表明: 三维精细化数值模型可以精确地反映地质构造对地下水位及水压力的影响, 使得分析结果更加符合实际情况; 水幕系统可以有效提高洞库水封安全性, 具体表现为, 在无水幕条件下进行洞室开挖时, 地下水位明显下降, 部分洞室上方出现疏干区, 而在有水幕条件下进行洞室开挖时, 地下水位下降不明显, 洞室上方具有较厚的含水层, 其厚度足以保证洞室水封安全性; 同时, 洞室涌水量在可控范围内。本研究提出的地下油库水封安全评价方法对类似工程具有借鉴意义。
Abstract:Objective The principle of a "gap storage water seal" is used to realize large-scale underground storage of crude oil, in which water-sealed safety is an important prerequisite for the safe and economical operation of underground oil storage.
Methods To evaluate the water-sealed safety of underground oil storage, based on a refined engineering geological survey, the permeability coefficients of cavern surrounding rock, fault zones, dense joint fracture zones, and broken zones are obtained accurately, and the spatial variation of the permeability coefficient within the reservoir area is comprehensively analysed. Combined with multi-source high-precision survey information, a three-dimensional refined seepage numerical simulation model is constructed. After comparing and analysing both advantages and disadvantages of the three-dimensional refined model and corresponding homogeneous medium model, a numerical simulation is carried out to compare and analyse the reliability of cave storage with or without a water seal, and the water inflow of cavern during construction and operation is also predicted.
Results Results show that the three-dimensional refined model can accurately reflect the influence of geological structures on the groundwater level and water pressure, making analysis more in line with the real situation.The water curtain system can effectively improve the water-sealed safety of underground oil storage. Specifically, when the cavern is excavated without water curtain, the groundwater level drops significantly, and drainage area exists above some caverns. When the cavern is excavated under water curtain, the groundwater level does not drop significantly, and thick aquifer exists above the cavern, ensuring the water-sealed safety of underground oil storage; at the same time, the water inflow of cavern is under control.
Conclusion Assessment of the water-sealed safety of underground crude oil storage provided in this article can be used as a reference for other similar projects.
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图 10 地下水封油库储油原理示意图[22]
Figure 10. Schematic diagram of oil storage of underground water-sealed oil depot
表 1 洞库各区渗透系数和渗透张量修正结果
Table 1. Permeability coefficient and correction of the permeability tensor in each cavern area
分区 渗透系数主值/(m·d-1) 压水试验渗透系数/(m·d-1) 修正系数 修正后的渗透系数主值/(m·d-1) Ⅰ 3.97×10-4 8.87×10-4 2.27 9.02×10-4 3.53×10-6 8.01×10-6 3.94×10-4 8.94×10-4 Ⅱ 1.02×10-3 9.74×10-4 1.12 1.14×10-3 1.91×10-4 2.15×10-4 8.27×10-4 9.29×10-4 Ⅲ 1.12×10-3 1.95×10-3 2.01 2.25×10-3 6.49×10-4 1.31×10-3 9.79×10-4 1.97×10-3 Ⅳ 1.21×10-3 1.35×10-3 1.40 1.70×10-3 5.56×10-4 7.80×10-4 6.55×10-4 9.19×10-4 表 2 库区优势节理隙宽、结构面间距、倾向及倾角
Table 2. Dominant joint gap width, structural plane spacing, tendency and dip angle in the reservoir area
优势节理 隙宽/mm 结构面间距/m 倾向/(°) 倾角/(°) 西北区域优势节理1 0.09 1.05 250.0 70.0 西北区域优势节理2 0.09 1.22 155.0 70.0 东北区域优势节理1 0.07 0.70 255.0 65.0 东北区域优势节理2 0.08 0.83 70.0 12.5 东北区域优势节理3 0.06 0.61 170.0 67.5 西南区域优势节理1 0.05 0.60 230.0 75.0 西南区域优势节理2 0.05 0.58 155.0 60.0 东南区域优势节理1 0.08 0.91 240.0 70.0 东南区域优势节理2 0.08 0.98 185.0 70.0 表 3 库区断层、节理密集带以及破碎带渗透系数
Table 3. Permeability coefficient of the fault, joint dense zone and fracture zone in the reservoir area
断层 渗透系数/(10-2m·d-1) 节理 渗透系数/(10-3m·d-1) 破碎带 渗透系数/(10-3m·d-1) F1 1.95 J1 5.35 P2 6.45 F4 1.25 J2 9.11 P4 1.15 F5 1.24 J3 6.14 — J4
J57.13
6.77— — 表 4 洞库涌水量计算结果汇总
Table 4. Summary of water inflow calculation of caverns
数值模拟 工况 施工工序 涌水量/(m3·d-1) 施工期 开挖1层 1 785.5 开挖2层 2 017.2 开挖3层 3 380.0 运营期 1 032.0 -
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