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本文使用天然源超低频电磁探测仪对北京大学校园内两口地热井进行了超低频电磁探测试验,获得了1号地热井（京热119号井）连续五天、每天四个时刻的天然源超低频电磁探测数据以及2号地热井（京热168号井）单天的天然源超低频探测的数据.基于所获得的数据,开展了地热井的天然源超低频探测影响因素的研究,这些因素主要包括：天然源超低频电磁场和观测时间的关系、探头摆放方向与接收工频谐波干扰关系以及天气状况对观测数据质量的影响等.研究表明：(1)天然源超低频电磁探测信号存在明显的日夜交替变化,其中相对振幅-频率曲线在不同日期、同一邻近时刻总体的包络线具有较好的重复性和一定的稳定性;(2)工频谐波干扰场方向是影响因素之一,当仪器探头长轴方向与工频谐波干扰场的等效主轴方向平行时噪声影响最小;(3)雨天环境会对天然场源超低频信号中的高频部分造成较大影响. 相似文献
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《地球物理学报》2021,64(6)
极低频电磁探测方法(WEM)是一种新型人工源低频电磁探测技术,目前尚未见极低频电磁探测方法的海区研究,缺少相关经验.为测试WEM在海洋环境中的电磁响应特征,本文将"地-电离层"全空间电磁波传播理论应用到含海水介质的"地-电离层"全空间模型,由地表处数值格林函数出发,利用空气层与海水层界面谢昆诺夫势函数满足的边界条件,推导了海底界面的场强表达式.采用高采样密度的Hankel数字滤波方法进行数值模拟计算.为探究WEM在海洋油气资源探测中的适用性,建立简化海洋地电模型,通过分析WEM对不含异常体的背景场和含高阻油气异常体时的电磁响应曲线差异来检测WEM探测海底高阻油气层的可行性.并讨论不同观测方式、不同收发距以及海水层厚度、油气层埋深和油气藏厚度对WEM电磁响应特征的影响.研究结果表明,WEM可在数百千米收发距下探测浅海区域海底下方电性异常体的存在. 相似文献
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利用地震探测的方法获得地球深部精细构造,从而增强深部资源勘探和重大地质灾害预测能力,是目前地球物理学研究的热点之一.本文简要回顾了国内外深部地震探测研究的历史,分析和解释了在精确深部地震探测中保护低频地震信号的重要性和必要性.在此基础上进一步阐述了地震检波器的低频特性对获取高质量深部地震数据的意义,重点归纳总结了如何利用伺服技术、闭环极点补偿技术以及力平衡反馈技术实现地震检波器的低频拓展,并以典型深部地震探测项目为例介绍了低频检波器在深部探测中的应用及主要取得的成果.最后,结合新型材料和新型加工技术,指出了未来深部地震检波器发展的主要方向. 相似文献
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为了评价贵德盆地深部地热资源远景,使用V8仪器进行了地面大地电磁法和可控源音频大地电磁法工作,首次对贵德盆地深部电性特征和深部地热资源进行评价.查明贵德盆地基底埋深3600 m～4900 m.推断盆地第三系上新统贵德组（上部地层）是浅部热储层,其厚度为370 m;其埋深为530 m.老第三纪渐新统（上部地层）是中部热储层,其厚度为640 m～800 m,其埋深为1810 m～2330 m.侏罗纪、白垩纪地层是深部热储层,其厚度为970 m~1600 m;其埋深为3680 m～4990 m.提出浅部热储层属于盆地型层状热储;中深部热储层属于断裂型带状热储.推断出二条大断裂破碎带. 相似文献
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《中国科学:地球科学》2020,(9)
人工源电磁探测技术作为地球物理电磁探测的重要分支,在过去十年中得到快速发展.中国陆续攻克电磁探测方法的基础理论、正反演方法和核心装备技术难题,在地面电磁法、航空电磁法及海洋电磁法等领域的研究中取得了突破性进展,出现空-地-井立体探测和频-时域多尺度电磁探测新技术,实现对地下10km深度范围内目标体的有效探测.为了进一步满足国家在深部地质找矿、城市地下空间探测、地质灾害探测和监测等方面的迫切需求,仍需继续推动地球物理勘探方法的技术创新,发展高效、可靠、经济的新装备. 相似文献
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东营凹陷深部储层成层性较差,速度结构复杂,工区内井震关系不明确.本文首先通过地质成因分析,明确了研究区深部储层主要发育在沙四下和孔一中的"红层";通过对深部储层测井曲线的雷达图分析和交会分析,确定了SP、AC、GR、CNL、R4为东营凹陷深部储层的五种敏感测井响应;通过井震标定与地震剖面精细解释,完成了研究区井震构架的建立,明确了研究区储层符合薄互层的结构特征;在不同相带井震分析基础上,分别建立了沙四下和孔一中井震关系模板,有利于储层的定性甄别;通过定量研究多属性井震关系,得到了描述深层有利储层的最佳优势属性;最后开展基于多元线性回归和SVM的储层预测研究,找到了预测深部储层井震厚度关系的有效方法. 相似文献
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Behrooz Oskooi Mahmoud Mirzaei Behnam Mohammadi Mohammad Mohammadzadeh-Moghaddam Feridon Ghadimi 《Studia Geophysica et Geodaetica》2016,60(1):141-161
Magnetotelluric (MT) and ground magnetic surveys were conducted on the Mahallat geothermal field situated in Markazi province, central Iran, as a primary part of the explorations and developments of a geothermal energy investigation program in the region. Mahallat region has the greatest geothermal fields in Iran. MT survey was performed in November 2011 on an 8 km profile crossing the hot springs with a total of 17 stations. The 2D inversion of the determinant MT data was performed using a 2D inversion routine based on the Occam approach. The 2D resistivity model obtained from the determinant data shows a low resistivity zone at 800-2000 m depth and a higher resistivity zone above the low resistivity zone, interpreted as geothermal reservoir and cap rock, respectively. It also revealed two major concealed faults which are acting as preferential paths for the circulation of hydrothermal fluids. To obtain more geophysical evidence, a ground magnetic survey with 5000 stations was also performed over an area of 200 km2 around the MT profile. Magnetic measurements show a main positive anomaly of about +1000 nT over the study area, which could be interpreted as an intrusive body with the high magnetic susceptibility (i.e. mafic and ultramafic rocks) into the sedimentary host rocks. We interpret the body as the heat source of the geothermal system. Structural index and depth estimation of the anomaly indicate that the intrusive body is similar to a cylinder extending from about one kilometer depth down to greater depths. The results of MT and magnetic investigations indicate a geothermal reservoir which proves the preliminary geological observations to a great extent. 相似文献
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中低温对流型地热资源在华北地区广泛分布,是一种清洁的替代能源.与活动断裂带相关的水热型地热资源是中低温地热系统的重要组成部分.本文基于高精度重力测量、微动测深及钻孔温度测量等数据,从热源、通道、储层和盖层四个方面探讨了南口—孙河断裂带水热系统特征.低重力异常揭示的燕山期花岗二长岩、闪长岩岩体范围为23.8 km~2和14.3 km~2,放射性测井数据计算得到其生热率均值为3.14μW·m~(-3),侏罗系火山岩生热率均值为1.65μW·m~(-3),隐伏岩体和火山岩均难以构成地热系统的附加热源.重力异常显示南口—孙河断裂带宽度约500~800 m,断裂带切割蓟县系雾迷山组白云岩热储层.钻井温度曲线显示断裂带内水热活动强烈,说明该断裂带是导水、导热的重要通道.断裂带南西侧马池口一带第四系松散层与侏罗系火山岩形成了热储盖层,微动测深显示火山岩最大厚度约1500 m.综上源、通、储、盖四个要素分析,该地热系统为热传导一对流复合型,来自京西北山区的大气降水经远距离径流深循环吸收地层热量后沿南口—孙河断裂上移到达裂隙发育的白云岩地层中形成热水.总之,沿南口—孙河断裂带具备了良好的地热地质条件,可达到规模开采的条件. 相似文献
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Geophysical monitoring and evaluation of coastal plain aquifers 总被引：1，自引：0，他引：1
We use time domain electromagnetic (TDEM) soundings to monitor ground water conditions beneath the coastal plain in eastern North Carolina. The TDEM method measures the earth's response to an induced electromagnetic field. The resulting signal is converted, through a complex inversion process, to apparent resistivity values, which can be directly correlated to borehole resistivity logs. TDEM soundings are used to map the interface between fresh and salt water within coastal aquifers, and estimate depth to basement when siting new monitoring wells. Focused TDEM surveys have identified areas of salt water encroachment caused by high volumes of discharge from local supply wells. Electromagnetic sounding, when used in tandem with the state's network of monitoring wells, is an accurate and inexpensive tool for evaluating fresh water/salt water relationships on both local and regional scales within coastal plain aquifers. 相似文献
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P. Piña-Varas J. Ledo P. Queralt A. Marcuello F. Bellmunt R. Hidalgo M. Messeiller 《Surveys in Geophysics》2014,35(4):1045-1064
The resistivity structure of the Tenerife geothermal system has been determined by the 3-D inversion of data from different magnetotelluric surveys. In this paper, the ocean and topography effects on the magnetotelluric data were investigated by constructing a 3-D conceptual geoelectrical model of the island. The study showed that these effects should be taken into account in order to obtain a reliable subsurface model of the island. Data from 148 sites were used during three-dimensional inversion. The most interesting feature in the final geoelectrical model of the geothermal system is a low resistivity structure (<10 Ωm) above the resistive core of the system. The low resistivity structure has been interpreted as a hydrothermal clay alteration cap typically generated in the conventional geothermal systems. The resistivity model has been correlated with a recent seismic velocity model, showing that a low resistivity structure surrounds an area with high P wave velocity and medium–high resistivity. This medium–high resistivity area can be associated with a slowly solidified magma and, therefore, with a hotter part of the geothermal system. 相似文献
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Magnetotelluric resistivity modeling for 3D characterization of geothermal reservoirs in the Western side of Mt. Aso, SW Japan 总被引：1，自引：1，他引：1
Hisafumi Asaue Katsuaki Koike Toru Yoshinaga Shinichi Takakura 《Journal of Applied Geophysics》2006,58(4):296
Geothermal reservoirs are usually located at a depth range of 2 to 5 km, so to efficiently utilize such resources an advanced prospecting method is needed to detect these deep geologic structures. This study aimed to three-dimensionally characterize geothermal reservoirs by a combination of Magnetotelluric (MT) survey, inversion analysis of apparent resistivity, and interpolation of the resistivity data obtained. The western side of Mt. Aso crater, southwest Japan, was chosen as the case study area. Three hot springs exist there and a fault is assumed to go in the direction connecting them. A MT survey was carried out at 26 sites and the data processed by a remote reference method to reduce artificial noises. Based on skewness and Mohr circle analyses of the impedance tensor, the local geologic structure at each site could be approximated as horizontally layered and therefore, a one-dimensional inversion analysis was applied to the MT raw data. The resultant resistivity column data were then interpolated by the three-dimensional optimization principle method. The resistivity distributions obtained clarified continuous conductors with especially low resistivity (less than 10 Ω·m) at the hot springs along the fault. Because the resistivity decreases largely with an abundance of clay minerals, the conductors could be considered to correspond with the cap rocks. Thus, two geothermal reservoirs, whose shapes were estimated to be pillar, were detected under the cap rocks in an elevation range of − 1000 to − 3000 m. By comparing the resistivity distributions with the temperature distributions based on fluid-flow calculations at a steady state using FEM, the validity of the location and dimension of the estimated reservoirs were confirmed. 相似文献
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Y. Yamaya P. K. B. Alanis A. Takeuchi J. M. Cordon Jr. T. Mogi T. Hashimoto Y. Sasai T. Nagao 《Bulletin of Volcanology》2013,75(7):1-13
Taal Volcano, located in the southwestern part of Luzon Island, Philippines, has frequently experienced catastrophic eruptions from both the Main Crater on Volcano Island and flank eruptions. These eruptions have been magmatic, phreatomagmatic, and hydrothermal, with the latter implying the existence of a large-scale hydrothermal system beneath the volcano. We conducted an electrical resistivity survey using the magnetotelluric method in order to identify the location and geometry of the hydrothermal reservoir and sealing cap rock. Two-dimensional inversion using the observed data indicates four similar resistivity sections. The structure at shallow depths corresponds to volcanic deposits and an aquifer. Below 1 km, the structure features a relatively resistive zone beneath the main crater surrounded by a conductive shell. We interpreted these to be a large hydrothermal reservoir with an impermeable cap rock sealing it. Recent ground deformation detected by GPS measurements suggests that the hydrothermal reservoir is active. The interpreted cap rock thins just beneath the main crater and could easily be destroyed by an imbalance in the hydrothermal system. We conclude that this hydrothermal reservoir plays a significant role in driving catastrophic eruptions that begin with a hydrothermal explosion at the main crater. 相似文献
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为解决内蒙古白旗地区水资源严重短缺的问题,采用瞬变电磁技术进行水资源勘察.本文通过分析平原地区含水层的矿化度和孔隙度对岩石电阻率的影响,得出在内蒙古干旱牧区浑善达克沙地的含水砂砾岩电阻率值为75~150 Ω·m之间变化.以导电球体为模型来计算地下含水层异常的可分辨时间窗口,确定该区地下含水层异常出现最大值的探测条件.瞬变电磁技术在结合已知自流井的电性差异基础上,可以对地下水的含水层和含水深度进行准确勘察,确定新的水井5位置,经钻孔验证喷水量达到每小时100 m3以上,满足白旗供水需求.验证了瞬变电磁技术在地下水资源勘察中的有效性,为西部地区水资源的评价提供了重要的技术依据. 相似文献
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Illuminating and optimising a three‐dimensional model of an oil shale seam and its volume distribution using the transient electromagnetic induction method,central part of Jordan 
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下载免费PDF全文 The oil shale exploration program in Jordan is undertaking great activity in the domain of applied geophysical methods to evaluate bitumen‐bearing rock. In the study area, the bituminous marl or oil shale exhibits a rock type dominated by lithofacies layers composed of chalky limestone, marls, clayey marls, and phosphatic marls. The study aims to present enhancements for oil shale seam detection using progressive interpretation from a one‐dimensional inversion to a three‐dimensional modelling and inversion of ground‐based transient electromagnetic data at an area of stressed geological layers. The geophysical survey combined 58 transient electromagnetic sites to produce geoelectrical structures at different depth slices, and cross sections were used to characterise the horizon of the most likely sites for mining oil shale. The results show valuable information on the thickness of the oil shale seam at 3.7 Ωm, which is correlated to the geoelectrical layer between 2‐ and 4 ms transient time delays, and at depths ranging between 85 and 105 m. The 300 m penetrated depth of the transient electromagnetic soundings allows the resolution of the main geological units at narrow resistivity contrast and the distinction of the main geological structures that constrain the detection of the oil shale seam. This geoelectrical layer at different depth slices illustrates a localised oil shale setting and can be spatially correlated with an area bounded by fold and fault systems. Also, three‐dimensional modelling and inversion for synthetic and experimental data are introduced at the faulted area. The results show the limitations of oil shale imaging at a depth exceeding 130 m, which depends on the near‐surface resistivity layer, the low resistivity contrast of the main lithological units, and the degree of geological detail achieved at a suitable model's misfit value. 相似文献
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In 1979 and 1980, 535 magnetotelluric soundings using a frequency range of 1700 Hz-8 Hz were performed on the island of Réunion for geothermal exploration.Few direct hot-water discharges were observed. Consequently, geophysical methods, particularly the audiomagnetotelluric method, were used extensively. Favourable geological conditions for this method were encountered and the results, which were controlled using classical electrical methods on test areas, suggest an unusual distribution of resistivities for lava flows situated above suspected geothermal areas. These layers progressively decrease in resistivity down to a very conductive layer. In areas where these conductive layers were nearest the surface, detailed studies were carried out showing a close correlation between decreasing resistivity and increasing hydrothermal alteration. In addition, gradient wells reveal high geothermal gradients in such areas. The conductive layers revealed by audiomagnetotelluric soundings seem to correlate with thermal effects creating progressive hydrothermal alteration from an inferred hot-water reservoir up toward the surface. 相似文献