Electrical structure identification of deep shale gas reservoir in complex structural area using wide field electromagnetic method

To fully exploit the technical advantages of the large-depth and high-precision artificial source electromagnetic method in the complex structure area of southern Sichuan and compensate for the shortcomings of the conventional electromagnetic method in exploration depth,precision,and accuracy,the large-depth and high-precision wide field electromagnetic method is applied to the complex structure test area of the Luochang syncline and Yuhe nose anticline in the southern Sichuan.The advantages of the wide field electromagnetic method in detecting deep,low-resistivity thin layers are demonstrated.First,on the basis of the analysis of physical property data,a geological–geoelectric model is established in the test area,and the wide field electromagnetic method is numerically simulated to analyze and evaluate the response characteristics of deep thin shale gas layers on wide field electromagnetic curves.Second,a wide field electromagnetic test is conducted in the complex structure area of southern Sichuan.After data processing and inversion imaging,apparent resistivity logging data are used for calibration to develop an apparent resistivity interpretation model suitable for the test area.On the basis of the results,the characteristics of the electrical structure change in the shallow longitudinal formation of 6 km are implemented,and the transverse electrical distribution characteristics of the deep shale gas layer are delineated.In the prediction area near the well,the subsequent data verification shows that the apparent resistivity obtained using the inversion of the wide field electromagnetic method is consistent with the trend of apparent resistivity revealed by logging,which proves that this method can effectively identify the weak response characteristics of deep shale gas formations in complex structural areas.This experiment,it is shown shows that the wide field electromagnetic method with a large depth and high precision can effectively characterize the electrical characteristics of deep,low-resistivity thin layers in complex structural areas,and a new set of low-cost evaluation technologies for shale gas target layers based on the wide field electromagnetic method is explored.

Distributed wide field electromagnetic method based on high-order 2^(n) sequence pseudo random signal

To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this method,only one set of high-order pseudo-random waveforms,which contains all target frequencies,is needed.Based on high-order sequence pseudo-random signal construction algorithm,the waveform can be customized according to different exploration tasks.And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements.A field test in the deep iron ore of Qihe−Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time.Compared with traditional controlled-source electromagnetic methods,the distributed WFEM is much more efficient.Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.

Application of wide-field electromagnetic method in shale gas survey in Eastern Kunlun,Qinghai province,China

In order to study the distribution of shale gas reservoir in the Babaoshan Basin of Eastern Kunlun,the wide-field electromagnetic(WFEM)survey was carried out to obtain the spatial distribution characteristics of the underground electrical volume resistivity based on the delineation of the scope of the Babaoshan Basin by regional gravity data.The basic characteristics of the basement,basin framework,and extension,vertical change,burial depth of dark mud shale in this area were identified,and the electrical distribution of the Babaoshan mud shale horizon was revealed,which has been proved to be a good geological effect by drilling.The exploration results show that the WFEM has significant effects on the exploration of shale gas occurrence strata,which meets the needs of investigation and evaluation of multi-layered and large-scale shale gas,and plays a good demonstration role in the follow-up shale gas exploration.

A differential wide field electromagnetic method and its application in alkaline-surfactant-polymer(ASP) flooding monitoring

To improve effectiveness of ASP flooding, it is necessary to establish a reliable parameter design and tracking adjustment method to monitor the process of oil displacement. A differential wide field electromagnetic method was proposed and applied to the ASP displacement monitoring test in a block of the Daqing Oilfield. In the process of ASP flooding, the electromagnetic field was measured many times. The data acquired before the ASP flooding were set as the background field, and the resistivity model was obtained by inversion. Then, the resistivity data were calibrated by logging data and the resistivity model was established. Finally, the range and front of ASP flooding were deduced with the residual gradient from the spatial domain first-order difference of the resistivity model. Production data of well groups in this block have proved that this method can work out the range and front of ASP flooding accurately, providing support for optimization of ASP flooding parameters.

Application of pseudo-random frequency domain electromagnetic method in mining areas with strong interferences

Due to the strong electromagnetic interferences and human interference,traditional electromagnetic methods cannot obtain high quality resistivity data of mineral deposits in Chinese mines.The wide field electromagnetic method(WFEM),in which the pseudo-random signal is taken as the transmitter source,can extract high quality resistivity data in areas with sever interference by only measuring the electric field component.We use the WFEM to extract the resistivity information of the Dongguashan mine in southeast China.Compared with the audio magnetotelluric(AMT)method,and the controlled source audio-frequency magnetotelluric(CSAMT) method,the WFEM can obtain data with higher quality and simpler operations.The inversion results indicate that the WFEM can accurately identify the location of the main ore-body,which can be used for deep mine exploration in areas with strong interference.

伪随机广域电磁法自动采集系统关键技术

针对川藏铁路、西南山区等高海拔的勘探,急需一套自动采集电磁勘探系统。本文基于伪随机广域电磁法和自动控制技术,攻克了伪随机多频信号发送与接收相结合的自动控制的难题。首先根据2n伪随机序列信号,生成多频波可控信号源,并推导了伪随机多频波信号的自动采集时间节点控制公式;接着设计了一套自动采集参数结构表和通信控制方法,用于实现在不同设备间的参数交互;最后在伪随机广域电磁法装备上编写自动采集控制核心算法,实现了伪随机广域电磁法自动采集系统。结果表明:通过实验测试,自动采集系统可以得到准确的时间域和频域数据,同时工作时间上节省20%,人力资源上可以节省71%。伪随机广域电磁法的自动采集功能实现了非技术人员介入的数据采集,可降低施工成本,提高勘探效率,尤其是在类似于川藏铁路的勘探中,可由登山队员或当地藏民携带仪器进行数据采集。

辽东郑屯地区基于广域电磁法的深孔验证

辽东金矿床的发育被认为受变质核杂岩体系叠加拆离断层带控制,传统观点判定永宁盆地永宁组盖层厚度达到几千米以上,阻碍含矿流体的运移的同时,不利于形成大规模金属矿床。辽东地区矿床深部探测投入少、研究程度低,勘查探测深度长期局限于1 km以内。本文在郑屯地区采用广域电磁法获得了3 km以浅的电阻率分布特征,厘清了辽东盖层厚度为千米左右,突破了对永宁组巨厚盖层的传统认识;进一步施工2 km深钻开展验证,在孔深1 345 m处发现永宁组地层与下伏太古宙基底呈不整合接触关系,界面附近未见明显的构造拆离迹象。本研究证实永宁盆地盖层厚度仅为千米左右,结合区内多期活动断裂构造和密集分布的浅成岩脉群,初步判定永宁盆地的成矿地质背景类似胶东金矿集区,推测存在华北克拉通破坏时期含矿变质流体或岩浆热液运移至界面上部成矿的可能。辽东地区具有实现多金属找矿突破的潜力,广域电磁法勘探为深地成矿预测指明了方向。

湘南铜山岭矿田构造‒成矿特征以及深部成矿预测

湘南铜山岭矿田位于南岭成矿带与钦杭成矿带的结合部位。本文采用构造解析、广域电磁探测、热液矿物地球化学分析等方法对铜山岭矿田1~3 km深度的构造‒岩浆‒成矿系统特征进行了综合研究。研究结果表明:①构造解析显示铜山岭矿田经历了三期构造事件,第一期为成矿前的NWW-SEE向挤压,形成NNE向褶皱和逆断层,以及NWW向张性断裂;第二期为成矿期的NW-SE向伸展,使部分NNE向逆断层转化为正断层,并伴随花岗岩体侵位以及矽卡岩型铜多金属成矿事件;第三期为成矿后的近SN向挤压,使NNE向断层发生左行走滑。成矿前形成的NNE向断层在成矿期重新活动,并成为矿田内主要的控岩控矿断层。②广域电磁法探测表明矿田覆盖区深部的隐伏花岗岩岩体与灰岩地层之间存在较大的物性差异,异常解译结果显示高阻体为花岗岩岩体,层状低阻体为灰岩地层,陡倾低阻体为区域性断层,其中高阻体与层状低阻体之间的过渡带是有利的成矿空间。③断层中发育两期方解石脉,其中第二期方解石脉的地球化学特征指示其与岩浆热液活动有关。基于以上研究我们在铜山岭矿田圈定两个深部成矿预测区。

胶东牟乳成矿带邓格庄金矿区深部构造特征及成矿预测

牟乳成矿带是胶东重要的金成矿带之一,为金矿集中分布区,是国内外金矿勘探和研究的热点。近年来,胶东金矿成矿规律和找矿理论不断取得新认识,尤其是热隆—伸展成矿理论的提出为深部找矿提供了理论基础。热隆—伸展成矿理论更加凸显出构造对金成矿的重要意义,深部构造研究由此显得尤为重要。广域电磁法是何继善院士团队研发的一种人工源频率域电磁勘探方法.

论电场近区双频测深的可行性

非平面波区测深是频率域电磁勘探方法理论发展的重要动力。广域电磁法不对非平面波区电磁场表达式做简化,通过迭代求解获取全区视电阻率,极大拓展了人工源频率域电磁法的观测空间范围与探测深度。E-Ex模式是现今最为常用的广域电磁法观测模式,但其近区测深能力有限。本文探讨了两种广域电磁法E-Ex模式近区双频测深方案的可行性。首先,简述了高阶近似和低阶近似两种近区电场双频测深视电阻率计算方案的基本原理;然后采用一维模型进行数值模拟,对比了半空间模型中E-Ex模式不同场成分的强度与感应数的关系,计算了典型地电模型的视电阻率,分析了频率间隔及观测误差等对计算结果的影响。结果表明:高阶近似方案基本不具备可行性;低阶近似双频测深方案在理想条件下可以获得近区地电介质的变化信息,对地下低阻层反映更为灵敏,受观测角度、接地导线偶极长度及观测频率间隔等因素影响均较小,但对观测数据误差极为敏感,观测总场中较小的误差也将导致近区视电阻率信息提取失败。因此,广域电磁法E-Ex模式近区双频测深方案实际应用的关键在于控制观测精度。

广域电磁法在山东济阳坳陷氦气探测中的应用

利用广域电磁法在山东济阳坳陷氦气富集区开展方法实验,采用“电磁勘探资料处理解释一体化系统”进行广域电磁法数据处理与反演成像,获得地下3 km深度范围内的地层电阻率分布特征;建立了广域视电阻率与试验区盖层、储层之间的电性关系,同时也揭示了深部断裂构造与氦气运移通道之间的关系。在综合研究的基础上,基本查明了区内氦气主要储层馆陶组、东营组、沙一段、沙三段地层分布、厚度及氦气运移通道、构造圈闭等信息,形成了适用于济阳坳陷氦气勘探的广域电磁数据采集及处理方法,丰富了济阳拗陷氦气探测研究成果,为进一步推动济阳拗陷氦气勘探提供地球物理参数。

广域电磁法在强干扰碳酸盐岩矿区的应用探索

目前中国各成熟矿山大多面临浅部资源量不足的危机,对深部资源勘探的需求在不断增强。在实际勘探应用中,除了要进行大深度高精度探测,还要克服复杂地形与强电磁干扰的影响,因此对勘探技术提出了更高的要求。本文采用广域电磁法,在地形复杂且电磁干扰严重的云南某碳酸盐岩矿区开展了应用探索研究。结果认为广域电磁法在复杂碳酸盐岩矿区能够有效地压制干扰,对断层和已知矿体反映明显。据此在矿区深部圈定了可能的矿致异常,为矿区深边部找矿提供了指示方向,在复杂地形强电磁干扰的碳酸盐岩矿区开展攻深找盲探矿工作,广域电磁法能够实现高精度大深度探测,抗干扰能力强,工作效率高,可作为一种深部找探矿的技术手段。

人工源电磁法聚类分析处理技术在金属矿区的应用——以冬瓜山铜矿为例

人工源电磁法是一种重要的金属矿勘探方法。工业文明带来了复杂的噪声,含噪电磁响应信息的提取成为强干扰区电磁勘探的关键问题。本文提出了基于聚类分析的人工源电磁法去噪处理新技术,应用聚类分析对含噪频谱进行分类,以识别出具备人工源特征的功率谱数据,提高响应提取质量。实测数据处理结果表明,相较于常规处理方法,本文算法能够更好的压制噪声,提高人工源电磁法的数据预处理质量。

综合电磁法在凤太二里河铅锌矿深部的找矿效果分析

二里河铅锌矿是凤太矿集区中具有代表性的重要铅锌矿床之一,近些年找矿方向转向已知矿体深部及外围。根据二里河地区地质、地球物理特征,结合多年在凤太地区的综合地球物理找矿工作,分析了回线源瞬变电磁法、电性源短偏移距瞬变电磁法及广域电磁法在二里河地区的实际应用效果,对3种方法的特点和适用性进行总结,认为:回线源瞬变电磁法、电性源短偏移距瞬变电磁法及广域电磁法在该地区深部找矿具有可行性;回线源瞬变电磁法对于圈定矿体水平位置具有较好的效果,电性源短偏移距瞬变电磁法对低阻异常较为敏感,广域电磁法分辨率较高,同时探测深度可达到2500 m。此外针对二里河矿区的找矿工作,提出物探工作建议:采用以广域电磁法和电性源短偏移距瞬变电磁法为首选的综合电磁探测方法,同时应尽可能采用长剖面和面积性物探工作。

分布式三维广域电磁法在山东齐河—禹城李屯厚覆盖区富铁矿勘查中的应用

近年来,山东齐河—禹城李屯厚覆盖区富铁矿勘查取得了重大进展,但该区新生界厚度大(900~1100 m)、磁铁矿体埋藏深,矿体引起的地球物理异常弱,找矿难度大。为了揭示李屯富铁矿深部地质构造,开展了分布式三维广域电磁探测,应用高阶2n序列伪随机信号,一次发射49个频率并同时接收,实现分布式滚动测量,获得了地下2000 m以浅地电特征,并对地下地质结构进行解释,构建了重点研究区的三维地质模型,解释结果与已有的二维地震和钻探信息吻合度较高,为重磁联合反演提供有效的地质结构约束,结合重磁场特征和成矿规律圈定新的找矿靶区。结果表明,分布式三维广域电磁法是获取厚覆盖地区深部地质结构的有效探测方法,具有良好的应用前景。

广域电磁法在滇西北斑岩铜矿中的应用研究

普朗超大斑岩型铜多金属矿床产于石英闪长玢岩-石英二长斑岩-花岗闪长斑岩复式侵入体内,其成矿作用跟岩体密切相关,为了探测矿区深部隐伏岩体的形态及规模,拓展深部找矿空间,运用广域电磁法在矿区进行测深勘探。对采集数据进行了精细处理和综合地质解译分析,成果显示广域电磁法能有效地识别深部隐伏岩体和大型构造,通过与施工钻孔揭露的地质信息对比,较完整且规模较大的花岗岩体电阻率更稳定,本方法对岩性分界线响应的准确度也更高。探测结果表明矿区东侧和南部的深部还存在大范围复式岩体,在岩体内构造裂隙发育地段具有较大找矿潜力,可为后期优选深部找矿靶区提供地球物理参数。

广域电磁法在黄沙坪铅锌多金属矿田深部探测中的应用

位于南岭成矿带中段北缘的黄沙坪铅锌多金属矿田,是湖南省最大的铅锌矿产地,其开采历史悠久,基础地质研究程度较高。目前矿区面临资源枯竭与接续问题,亟需开展地球物理深部探测,预测及寻找深部隐伏矿体。本文采用广域电磁法探测研究区深部地质构造和隐伏岩体的形态及规模,拓展深部找矿空间。探测结果表明:广域电磁法在本区能较好的识别深部地质信息,矿区深部还存在大范围岩体,在岩体与围岩接触带仍具有较大找矿潜力。

个旧高松矿田广域电磁法深部探测与综合找矿研究

个旧超大型锡多金属矿床开采历史悠久,成矿作用和矿化类型复杂多样。随着浅部资源的消耗,如何寻找深部接触交代矽卡岩型锡多金属矿和层间硫化物型锡多金属矿,成为个旧高松矿田亟待解决的重要课题。为推动高松矿田中深部找矿突破,本文将广域电磁法应用到高松矿田进行深部探测,查明了深部地质体的分布形态;综合分析了矿田成矿地质特征,总结了矽卡岩型矿体和层间硫化物型矿体的矿床地质特征;同时结合广域视电阻率特征,建立了高松矿田两种主要矿床类型的地质-地球物理模型,以此模型进行成矿有利区预测,可为个旧地区及国内其他类似多金属矿的地球物理勘探提供参考和借鉴。

崇阳高枧钨、金多金属矿区找矿方向探讨

崇阳高枧钨、金多金属矿区位于长江中下游钨、金多金属成矿带,前人在此虽开展了大量矿产勘查和科研工作,但对该区深部成矿认识却无新进展,为探寻该地区深部找矿信息,笔者通过开展重磁异常特征、CSAMT异常剖面、广域电磁法剖面等工作,在高枧矿区南部发现的一处重磁低值正异常,并对2线,3线深部异常的电阻率中高阻隆起等现象进行研究,推断隐伏岩体分布于研究区西南部,其矽卡岩化接触带有利于W元素富集,是寻找矽卡岩型白钨矿的有利部位。推测高枧地区可能存在深部岩体,其位置应该在高枧西南部,区域空间位置显示岩脉最有可能来源于幕阜山岩体,两条北北东向断层形成了岩浆与矿液有利的运移通道。

广域电磁法在煤矿水患探测中的应用研究

煤矿水害探查的主要方向是探测煤层顶底板含水层的富水性和构造的含(导)水性。以安徽一煤田广域电磁勘探为例,通过分析广域电磁法的基本原理、野外施工技术、资料处理和解释方法,明确了广域电磁法可以作为1种新兴的物探手段用于煤矿防治水工作中。在探测过程中运用震电数据多属性融合技术减少物探异常解释的多解性,提高了勘探精度,为煤矿防治水工作提供了可靠的参考。