Interference analysis of the water level observation at Ganhai Double Wells in Yanyuan County, Sichuan Province
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摘要: 依据观测日志、降雨、水温监测和周边调查,对四川盐源干海双井水位观测干扰事件进行了详细的分类,按分类统计了干海井和干海机井干扰特征,以更加准确有效地识别与排除干扰。针对发生最为频繁的且对正常观测影响最大的堵塞和人为清洗干扰提出了初步技术解决方案。氢氧同位素分析结果表明双井井水受大气降雨补给,可通过收集降雨、河水资料来识别降雨干扰。Abstract: According to the observation logs, precipitation, temperature monitoring and surrounding investigation, the interference events with the characteristics of the water level observation of the double wells in Ganhai are classified in detail to identify and eliminate interference more accurately and effectively. A preliminary technical solution is proposed for the blockage and man-made cleaning interference that occur most frequently and have the greatest impact on normal observation. The results of hydrogen and oxygen isotope analysis show that the water from two wells is recharged by atmospheric rainfall. Rainfall interference can be identified by collecting rainfall and flow data of river.
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表 1 干海双井基础信息
Table 1. The basic information of Ganhai double wells
观测点 经度/° 纬度/° 海拔/m 钻孔深度/m 仪器类型 监测频率 类型 数字化测项 干海井 101.46 27.48 2286 79 SWY-Ⅱ型数字式水位仪 1次/分钟 动水位 气氡、水位、水温、气温、气压、降雨量 干海机井 101.47 27.47 2303 187 ZKGD3000-N型 1次/分钟 动水位 水位、水温、气压 表 2 水位正常动态类型
Table 2. Dynamic types of the normal water level
大类 基本类型 说明 多年趋势动态 趋势上升型 不多见,只见于油气田外围地区,大面积长期注水 趋势下降型 地下水过量开采,开采量超过大气降雨的渗入补给 趋势平稳型 开采量与补给量均衡/含水层封闭 年动态 上升、下降、平稳、起伏型 月、多日、日动态 固体潮效应微动态 气压效应微动态 表 3 2021年干海双井干扰统计表
Table 3. The interference statistics of Ganhai double wells, in 2021
监测点 干扰类型 发生次数 干扰特征 持续时间/分钟 数据变化幅度/m 最长时间 平均时间 最大变化幅度 平均变化幅度 干海机井 7 1050 607.1 0.18 0.13 人为(抽水灌溉) 1 170 170.0 0.16 0.16 降雨 4 1050 705.0 0.18 0.13 不明原因 2 810 630.0 0.14 0.11 干海井 54 1800 139.4 0.76 0.07 人为(维护水温观测装置) 3 157 89.3 0.1 0.08 人为(清洗) 37 1800 93.2 0.31 0.05 人为(改造井口装置) 3 120 50.0 0.76 0.39 降雨 2 360 265.5 0.04 0.03 观测系统堵塞 3 270 96.7 0.02 0.02 不明原因 6 1320 473.8 0.1 0.05 表 4 干海双井水化学成分及氢氧同位素分析结果
Table 4. Water chemical composition and hydrogen isotope analysis results of Ganhai double wells
观测点 δD/‰ δ18O/‰ Na+ K+ Mg2+ Ca2+ Cl− SO42− CO32− HCO3− 井水类型 mg/L 干海井 −108.9 −14.7 161.2 1 4.1 37.5 105.4 15.9 0 303.2 HCO3·Cl-Na 干海机井 −121.5 −16.3 773.2 4.8 28 111.2 1514.3 29.2 0 287.7 Cl-Na 表 5 地表水体渗入补给干扰的最大影响距离
Table 5. The Maximum influence distance from the surface water infiltration recharge interference
井区水文地质条件分区 含水层渗透性分级 最大影响距离/km 简单地区 弱透水层 1 中等地区 透水层 5 复杂地区 强透水层 10 表 6 地表水荷载作用干扰的最大影响距离
Table 6. The max impact distance of surface water load disturbance
荷载作用类型 最大影响距离/km 海潮荷载作用 10 水库荷载作用 6 江河水体荷载作用 粗砂与砾石含水层5 km 中砂含水层3 km 细砂与粉砂含水层1 km -
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