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1978年以来,LBL已经在每年工作的基础上取得不Cerro Prieto地区的重复的偶极-偶极电阻率资料。沿着一条从Cucupa山延伸到Mexicali谷中心和穿过目前开采区的唯一的测线上布设的测点,具有足够高的测量精度,一直在进行重复观测,以探测地下电阻率的变化。其中有一些变化可能与流体开采有关,最近大多数测量结果(1981.11)的精度平均约为1％。两年半的监测结果说明,现开采区的视电阻率每年增加5％,而就这个区的东部和西部,视电阻率每年都以相同的幅度减小。开采区电阻率增加很可能是由于较淡的水稀释了热储流体所致,采出的水中氯化物含量降低就是这种推断的依据。为了确定钻孔中特定岩层的电阻率是否随时间变化,我们设法比较了新孔与邻近旧孔的测井资料,结果表明,相距甚近的钻孔中,各地层单位的横向电阻率的变化足以掩盖电阻率随时间的变化部分。开采区东部电阻率减小的地区与陡峭倾斜的导电体,即与较高的热梯度带和该区内页岩厚度的增加有关。测井分析表明,低阻很可能由较高的温度所致,该区电阻率的减小可能是由来自深部温度更高、含盐分更多的盐水液体所引起的。最近的观测结果也表明,监测测线的西端近地表的电阻率急剧增加,这很可能是由于局部灌溉活动近期的变化所引起,这种灌溉能导致地下水质量的改观。为了考察地下水运动和化学反应所引起的电阻率变化现象,我们建议另增一条电阻率测线,穿过东部的开采区,并与现在的测线成60°交角,这条测线连同现在的测线将使我们获得未来开采区的基本数据(Cerro Prieto 2区和3区),这样就可建立一个观测网,以绘制地下水的运动图象。
Since 1978, the LBL has made repeated dipole-dipole resistivity data on the basis of its annual work without the Cerro Prieto region. Measuring points laid along a single survey line extending from the Cucupa hills to the center of the Mexicali valley and through the current mining zone have sufficiently high measurement accuracy that repetitive observations have been made to detect changes in the underground resistivity. Some of these changes may be related to fluid production, with the accuracy of most recent measurements (1981.11) averaging about 1%. Two and a half years of monitoring indicate that the apparent resistivity of the existing mining areas increases by 5% per year, while in the eastern and western parts of the area, the apparent resistivity decreases by the same amplitude each year. The increase in resistivity in the mining area is most likely due to dilution of the thermal storage fluid with lighter water, and the reduction of chloride in the produced water is the basis for this extrapolation. In order to determine whether the resistivity of a particular rock formation in a borehole has changed over time, we have tried to compare the log data of the new and adjacent old holes. The results show that the lateral resistivity changes of the strata in closely spaced boreholes Enough to cover up the resistivity changes over time. Areas with reduced resistivity in the eastern part of the mining area are associated with steeply inclined conductors, ie, with higher thermal gradient zones and increased shale thickness in the area. Log analysis shows that low resistance is likely to be caused by higher temperatures, and the decrease in resistivity in this zone may be caused by brine from deeper temperatures and more salinity. Recent observations have also shown that the near-surface resistivity at the western end of the monitoring line has risen sharply, most likely due to recent changes in local irrigation activity that can lead to improvements in groundwater quality. In order to examine the resistivity changes caused by groundwater movement and chemical reactions, we propose to add another resistivity line through the eastern mining area and at an angle of 60 ° with the current line, which, along with the current The survey will allow us to capture the basic data of the future mining area (Cerro Prieto Zone 2 and Zone 3) so that a network of observations can be made to map the movement of groundwater.