综合地球物理勘探在齐齐哈尔地区低温地热系统调查中的应用——以HLD1井为例

随着我国"蓝天保卫战"打响,以及快速经济社会发展对清洁能源的需求急剧增加,地热资源因资源量巨大、分布广泛、清洁、可再生、利用率较高等优点,逐渐成为人们关注的热点.本文针对齐齐哈尔龙安桥地区的地热资源开展综合地球物理调查研究,方法包括有可控源音频大地电磁测深、大地电磁测深与反射地震勘探,通过对地热能控热要素——盖层、热储层、热源与导热通道的综合分析,查明了控热要素的空间配置关系,确立了该地区地热系统的成因模式,为该区低温地热资源调查提供有益的指导.通过研究发现,盖层主要为白垩系嫩江组与明水组的泥岩层,盖层厚度大,其中以嫩江组为主的低阻盖层主体埋深范围620 ～ 1020 m;热储层主要为白垩系泉头组、青山口组和姚家组的砂岩层,热储层厚度中等,主要埋深范围1050～ 1350 m;热源——盆地下部与基底的花岗岩、花岗斑岩等酸性岩体富含放射性元素,其衰变生热,以及下部幔源热向上热传导产生的热量;导热通道为热储层内部及下部断裂构造,这些断裂为热量的传导及热液的运移提供了运输通道.最后提出了该区的低温地热系统的成因模式为"层控热盖热储-岩体放射生热与地幔热共同供热-热传导与断裂通道共同导热"的热水系统成因模式.     

北京平原区西北部大地热流与深部地温分布特征

北京平原区蕴藏着丰富的中-低温水热型地热资源,其西北部分布着小汤山地热田和京西北地热田,两大地热田以南口—孙河断裂带为界.地热田及其外围地区基础的地热地质研究工作较少.为给地热学研究和地热资源精细勘探提供科学依据,本文基于前人23眼钻孔的温度测量数据以及近期完成的548件热导率和100件放射性生热率实测数据,研究了区域大地热流和0~4 km深部地温特征.结果表明：（1）研究区现今地温梯度为11.31~94.89℃·km^-1,平均值为31.79℃·km^-1;岩石热导率为0.895~5.111 W·（m·K）^-1,放射性生热率为0.257~2.305 μW·m^-3,大地热流为48.1~99.1 mW·m^-2,平均值为68.3 mW·m^-2,热流的分布受基底形态和断裂构造控制.研究区东部南口—孙河断裂带两侧小汤山和郑各庄地区为高热流异常区,中部马池口地区也存在局部高热流异常区.（2）在南口—孙河断裂带的不同位置,不同深度地层温度差异明显,体现出区域现今地温场不只受控于该活动断裂,更是多期次构造事件复合叠加的结果.（3）南口—孙河断裂带南侧存在两处有意义的较高地温异常区,分别为郑各庄异常区和马池口异常区,其中马池口异常区是未来地热开发利用有一定潜力的地区.     

京北地区热水水文地球化学特征与地热系统的成因模式

京北地热田包括小汤山和沙河2个次级地热田,呈三角形展布,东南部边界为黄庄-高丽营断裂,西南部边界为南口-孙河断裂,北部边界为阿苏卫-小汤山断裂。热储层为蓟县系雾迷山组、铁岭组和寒武系—奥陶系碳酸盐岩岩溶裂隙含水层,热储盖层为青白口系页岩、石炭系—二叠系砂页岩和侏罗系火山岩隔水层。该地热田地温场的平面特征是在小汤山镇和汤11井区出现2个高温区;垂向特征是随埋深加大,地温升高,但热储层内垂向增温率较低,热储盖层垂向增温率较高。该区雨水、地下冷水和热水的氢氧同位素组成基本上都落在克雷格降水线上,表明区内热水来源于大气降水。在地下水化学三线图解中,该区热水位于城区热水的下方,说明京北热水比城区热水更靠近冷水补给区。热水的3H值表现出北高南低的特点,14C年龄也由北往南逐渐增大,说明热水自北向南流动。由此认为,由北部山区渗入地下的大气降水,经小汤山以北的十三陵—桃峪口岩溶水分布区,跨过阿苏卫-小汤山断裂后发生深循环并被地热加温,流入京北地区后在该地区赋存,形成热田。根据上述特征,建立了京北地热田地热系统的成因模式并定义为京北中低温对流型地热系统     

共和盆地干热岩地热资源的成因机制:来自岩石放射性生热率的约束

共和盆地位于青藏高原东北缘,是我国重要的干热岩地热资源赋存区之一．成因机制研究是干热岩地热资源研究中最为基础与核心的工作之一,也是干热岩地热资源潜力精细评价和合理开发利用的重要依据．本文基于98块采自共和—贵德盆地岩石样品的放射性生热率数据,分析了盆地主要岩性岩石的放射性生热率分布特征,讨论了共和盆地干热岩地热资源的成因机制,并初步建立了干热岩地热资源的成因模式．研究表明,共和盆地恰卜恰地热区沉积岩（以泥岩和粉砂质泥岩为主）放射性生热率为1.21～2.02μW·m~(-3),平均值为1.67±0.29μW·m~(-3);以花岗岩和花岗岩闪长岩等为主的基底岩石的放射性生热率介于1.17～5.81μW·m~(-3)之间,平均值为3.20±1.07μW·m~(-3)．贵德盆地扎仓寺地热区沉积岩（以砂岩和泥质砂岩为主）放射性生热率为1.83～2.40μW·m~(-3),平均值为2.13±0.23μW·m~(-3);基底花岗质岩石的放射性生热率介于0.92～6.49μW·m~(-3)之间,平均值为2.81±1.40μW·m~(-3)．测试数据显示共和—贵德盆地基底花岗岩不存在高放射性生热率异常．但是,新生代以来印度—欧亚板块持续性陆-陆碰撞作用造成的壳内放射性生热元素富集层增厚,导致了花岗岩放射性生热率的热贡献量同步增大（30.3～40.5mW·m~(-2)）,因此,花岗岩放射性生热可为共和盆地干热岩地热资源提供稳定的壳内热源基础．基于放射性生热率数据和热流配分研究,结合研究区已有地质-地球物理研究资料,本文认为壳内部分熔融层作为附加热源为共和盆地干热岩地热资源提供了重要的附加热流贡献．在此基础上,本文初步构建了共和盆地干热岩地热资源成因模式：加厚地壳花岗岩放射性生热与壳内部分熔融层供热．     

世界地热田重力监测研究进展

水热型地热资源是我国地热开发利用的重要组成部分,长期以来水热型地热资源的持续开发导致了不同程度的地质环境变化,逐渐引起人们的重视,进行地热开采过程中的多方法动态监测十分必要.长周期重复的高精度重力测量可以监测地热田的储层水量和参数变化,为热储建模提供约束,进而为地热田评估及可持续开发提供重要数据,目前正成为研究热点.测量方法一般可分为相对重力测量、绝对重力测量和混合重力测量.本文回顾了世界上多个国家开展地热田重力监测的历史、主要成果和最新进展,梳理了地热田开展重力监测的方法技术,包括监测网布设、设备选择、测点高精度定位新技术、各项改正方法、数据处理和反演方法等,提出了在国内重要地热田开展高精度重力监测的建议.随着仪器设备和方法技术的进步,混合重力测量将成为地热田重力监测的发展重点.数据处理及三维反演是目前地热田重力监测的关键技术问题.     

加利福尼亚HONEY LAKE盆地低温地热资源的综合调查

为了探明加利福尼亚北部Honey Lake地区低温地热储,提出了综合调查研究、确定地热资源的区域性研究包括重力、红外、水温、水质分析,由电阻率测量绘制出5个异常区.为了详细说明地热资源的结构和潜力,用温度梯度和地震方法对三个异常区进行了更多的研究.重力数据显示本区的地堑构造;综合地震反射数据与地面电阻和温度梯度数据指出了有关的断层,这些数据支持了浅部热储由深循环加热大气降水沿断层带补给的解释.     

从地球物理场信息分析西宁盆地地热地质条件

在对西宁盆地进行可控源音频大地电磁测深(CSAMT)全面探测的基础上,结合以往重力、地震、大地电磁测深、直流电测深等物探资料综合解释,揭示了西宁盆地隆坳构造格局和盆地性状,据地温场分布特征探讨了热储类型,指出西宁盆地中西宁坳陷属张性、张扭性,具有地温场高、地温梯度大的特点,且热储类型具盆地传导兼断裂对流型特征;大通、平安坳陷属压性、压扭性坳陷,地温场、地温梯度相对较低,热储类型为盆地传导型.西宁断陷是地热开发有利地段.     

贵德盆地深部地热资源地球物理评价

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.     

新墨西哥州Valles破火山口Baca地热田的地质和地球物理评价

Baca热田一号井位于新墨西哥州中北部上-更新统的Valles破火山口西半部．蒸汽和热水主要由北东向的Redondo Creek地堑产生的,在那里,不到2km的深度井下温度就达260℃．从地层学的角度来讲,热储区可以描述为一个包括第三纪和第四纪火山岩和覆盖于前寒武纪花岗岩基底之上的中生代和第三纪沉积岩在内的五层序列．其形成主要受到与Rio Grande断裂系的活动性有着根本关系的断裂和断层的控制．从地球物理的角度来讲,破火山口西半部以重力值最小、电阻率低为特征．破火山口地区40mGal的重力极小值大部分是由于充填破火山口密度较低的火山岩和沉积岩造成的,或许与深部岩浆源无关．用二维重力模拟指出Redondo峡谷的前寒武纪基底深度在Valles破火山口东部至少是3km,并可超过5km．大地电流和大地电磁法测量表明,热储区与低电阻率有关,而且深部低阻层与用测井资料推断出的结晶岩储集层的深度相关良好．根据大地电流和大地电磁法的测量资料还找到开采区东、西部可能存在的断裂带．断裂带可能构成到Redondo Creek热储的边界．这些资料还表明了热储区位于北东-南西向与南北两条区域断裂线的交汇区．大地电磁测量结果也表明破火山口西缘的深部低电阻率与深部热流体有关．在地球物理和测井资料的基础上,我们对热储的大小做了三种预测．预测热储展布范围是10-30km2,这取决于认为含有深部地热资源的地区是Sulphur Creek还是Valle Seco．     

北京平原区断裂构造重力异常识别研究

区域重力异常蕴含丰富的断裂构造特征信息.采用小波多尺度分解、归一化总水平导数垂向导数(NVDR_THDR)和剖面2.5D重力异常反演方法对北京平原区高精度区域重力资料进行了处理,获得了主要断裂构造平面位置、长度、规模、汇交关系及深浅延伸特征,分析了利用重力异常识别断裂的效果.结果表明:(1)北京平原区NE向断裂平面延展长度大、连续性强,NW向断裂分段性明显,连续性弱,但NW向断裂对NE向断裂有切割改造迹象.近EW或SN向断裂分布较为局限.(2)主控断裂平面和垂向延伸特征差异明显,顺义断裂、孙河断裂、永定河断裂等为盖层断裂;南口断裂、孙河断裂西段、二十里长山断裂和张喜庄断裂为基底断裂;黄庄—高丽营断裂南段、南苑—通县断裂、礼贤断裂、夏垫断裂和皮各庄断裂东段为地壳断裂.(3)利用NVDR_THDR峰值异常带的连续性、幅值、宽度及错切关系可有效识别断裂的平面展布特征,通过小波变换获得的不同深度等效层异常结合2.5D剖面反演可有效研究断裂在基岩内部的深浅延伸情况,但重力异常的垂向分辨能力弱,断裂在新生界内部延伸特征需结合其他地质资料进一步分析.     

Interpretation of gravity data to delineate structural features connected to low-temperature geothermal resources at Northeastern Portugal

A great number of low-temperature geothermal fields occur in Northern-Portugal related to fractured rocks. The most important superficial manifestations of these hydrothermal systems appear in pull-apart tectonic basins and are strongly conditioned by the orientation of the main fault systems in the region. This work presents the interpretation of gravity gradient maps and 3D inversion model produced from a regional gravity survey. The horizontal gradients reveal a complex fault system. The obtained 3D model of density contrast puts into evidence the main fault zone in the region and the depth distribution of the granitic bodies. Their relationship with the hydrothermal systems supports the conceptual models elaborated from hydrochemical and isotopic water analyses. This work emphasizes the importance of the role of the gravity method and analysis to better understand the connection between hydrothermal systems and the fractured rock pattern and surrounding geology.     

Integrated interpretation of the magnetotelluric and magnetic data from Mahallat geothermal field,Iran

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.     

A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric resistivity survey: 2D resistivity modeling

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.     

被动式超低频电磁法在深部地热资源勘察中的应用——以JR-119井及JR-168井为例

分析了深部地热资源勘察中的地球物理电磁法应用现状,阐明了被动式超低频电磁法在深部地热资源勘察中的可用性和优势;重点论述了被动式超低频电磁法在深部地热资源勘察中的探测机理.利用北京大学研制的BD-6型被动式超低频电磁探测仪在京热119井和168井附近布点探测,在探测过程中利用硬件滤波和水平旋转探头方向的方法消除了工频50Hz的部分谐波干扰,同时探测曲线的重复性也非常好,得到了相应井位的超低频电磁探测数据.在对深部热水储层和盖层岩性界面进行地质解释后,得到热储层赋存深度的绝对误差为23-50 m,盖层岩性界面的相对误差小于6.3%.探测结果表明借助被动式超低频电磁探测仪,可以较准确地获得深部岩溶裂隙地热水的分布信息.     

郯庐断裂带是热异常带吗:来自断裂带南段热流的约束

郯庐断裂带是东亚最重要的断裂之一,在构造地质、岩石矿物、地震分布等领域得到了广泛的关注,然而少有针对郯庐断裂带地热学的研究.本文作者对郯庐断裂带南段7口钻井进行了系统测温,采用光学扫描法测试了6口钻井的142块岩心和13块露头样品的热导率,获得了6个高质量的热流数据.结合已发表的热流和地震剖面资料,我们获得了郯庐断裂带南段的岩石圈结构.研究表明,郯庐断裂带南段现今地温梯度从南到北有增大的趋势,介于21.8~30.3℃·km^-1.大地热流值介于44.0~81.7 mW·m^-2,平均61.4±10.8 mW·m^-2,表现为正常大地热流的特征,并非热异常带.最大热流值出现在庐枞盆地的大陆科学钻探井ZK03处,上地壳浅部极高的生热层很可能是高热流的主要因素.沿郯庐断裂南段地震带浅源地震发震带的底界和350℃等温面耦合较好,指示了深部结构的差异.     

用微振动勘探方法探测隐伏断裂构造

介绍了运用微振动勘探方法探测隐伏断裂构造的方法和思路,并对郯庐断裂带两条分支断裂进行了试验性勘探．通过与人工地震勘探结果对比分析,发现微振动勘探方法对隐伏断裂构造具有较好的空间定位能力,其对岩性差异面形成的断裂定位误差与人工地震勘探结果相当; 又因其具有较大的勘探深度,因而可以有效揭示勘探区域下方地层及断裂的空间分布特征及其接触关系,这对于识别和确定断裂构造的主破裂面具有重要意义. 但微振动勘探方法对地层或断裂构造细节特征的揭示能力较差．因此,在实际地层或断裂勘探中,宜采用人工地震勘探方法与微振动勘探方法相结合的方式确定断裂的深浅构造关系,可以用微振动勘探方法进行普查,在确定断裂初步位置及空间展布特征后,再选用人工地震勘探方法进行断裂精确定位．      

Geology of the platanares geothermal area, Departamento de Copán, Honduras

The Platanares geothermal area, Departamento de Copán, Honduras, is located within a graben that is complexly faulted. The graben is bounded on the north by a highland composed of Paleozoic (?) metamorphic rocks in contact with Cretaceous - Tertiary redbeds of unknown thickness. These are unconformably overlain by Tertiary andesitic lavas, rhyolitic ignimbrites, and associated sedimentary rocks. The volcanic rocks are mostly older than 14 Ma, and thus are too old to represent the surface expression of an active crustal magma body. Thermal fluids that discharge in the area are heated during deep circulation of meteoric water along faults in a region of somewhat elevated heat flow. Geothermometry based upon the chemical composition of thermal fluids from hot springs and from geothermal gradient coreholes suggests that the reservoir equilibrated at temperatures as high as 225 to 240°C, within the Cretaceous redbed sequence. Three continuously cored geothermal gradient holes have been drilled; fluids of about 165°C have been produced from two drilled along a NW-trending fault zone, from depths of 250 to 680 m. A conductive thermal gradient of 139°C/km, at a depth of 400 m, was determined from the third well, drilled 0.6 km west of that fault zone. These data indicate that the Platanares geothermal area holds considerable promise for electrical generation by moderate- to hightemperature geothermal fluids.     

Thermal Influence of an Alpine Deep Hydrothermal Fault on the Surrounding Rocks

Major fault zones in mountain areas are often associated with cold‐water circulations and hydrothermal pathways. Compared with the massif as a whole, the deep groundwater flows in these high hydraulic‐conductivity zones modify the thermal state of the surrounding rock. This paper examines the thermal effects of groundwater flow in the area around the steeply dipping La Léchère deep fault zone (LFZ, French Alps) and associated shallow decompressed zone. We used a 3D numerical model drawn up from groundwater circulation data to investigate the La Léchère hydrothermal system and the thermal state of the rock in the valley sides. Hydrothermal simulations showed that convective flow into the LFZ cools the valley sides and creates a thermal upwelling under the valley floor. An unsteady thermal regime that continues for about 10,000 years is also needed to obtain the temperatures currently found under the valley floor in the LFZ. Temperature‐depth profiles around the LFZ show disturbances in the thermal gradients in the valley sides and the valley floor. Convective heat transfer into the LFZ and the decompressed zone, and conductive heat transfer in the surrounding rocks produce an unsteady, asymmetric thermal state in the rock on both sides of the LFZ.     

THE DIFFERENCE OF DEPOSITION RATE IN THE BOREHOLES AT THE JUNCTION BETWEEN NANKOU-SUNHE FAULT AND HUANGZHUANG-GAOLIYING FAULT AND ITS RESPONSE TO FAULT ACTIVITY IN THE BEIJING AREA

Beijing plain area has been always characterized by the tectonic subsidence movement since the Pliocene. Influenced and affected by the extensional tectonic environment, tensional normal faulting occurred on the buried NE-trending faults in this area, forming the "two uplifts and one sag" tectonic pattern. Since Quaternary, the Neocathaysian stress field caused the NW-directed tensional shear faulting, and two groups of active faults are developed. The NE-trending active faults include three major faults, namely, from west to east, the Huangzhuang-Gaoliying Fault, Shunyi Fault and Xiadian Fault. The NW-trending active faults include the Nankou-Sunke Fault, which strikes in the direction of NW320°~330°, with a total length of about 50km in the Beijing area. The northwestern segment of the fault dips SW, forming a NW-directed collapse zone, which controls the NW-directed Machikou Quaternary depression. The thickness of the Quaternary is more than 600 meters; the southeastern segment of the fault dips NE, with a small vertical throw between the two walls of the fault. Huangzhuang-Gaoliying Fault is a discontinuous buried active fault, a boundary line between the Beijing sag and Xishan tectonic uplift. In the Beijing area, it has a total length of 110km, striking NE, dipping SE, with a dip angle of about 50~80 degrees. It is a normal fault, with the maximum fault throw of more than 1 000m since the Tertiary. The fault was formed in the last phase of Yanshan movement and controls the Cretaceous, Paleogene, Neogene and Quaternary sediments.There are four holes drilled at the junction between Nankou-Sunhe Fault and Huangzhuang-Gaoliying Fault in Beijing area. The geographic coordinates of ZK17 is 40°5'51"N, 116°25'40"E, the hole depth is 416.6 meters. The geographic coordinates of ZK18 is 40°5'16"N, 116°25'32"E, the hole depth is 247.6 meters. The geographic coordinates of ZK19 is 40°5'32"N, 116°26'51"E, the hole depth is 500.9 meters. The geographic coordinates of ZK20 is 40°4'27"N, 116°26'30"E, the hole depth is 308.2 meters. The total number of paleomagnetism samples is 687, and 460 of them are selected for thermal demagnetization. Based on the magnetostratigraphic study and analysis on the characteristics of sedimentary rock assemblage and shallow dating data, Quaternary stratigraphic framework of drilling profiles is established. As the sedimentation rate of strata has a good response to the activity of the basin-controlling fault, we discussed the activity of target fault during the Quaternary by studying variations of deposition rate. The results show that the fault block in the junction between the Nankou-Sunhe Fault and the Huangzhuang-Gaoliying Fault is characteristic of obvious differential subsidence. The average deposition rate difference of fault-controlled stratum reflects the control of the neotectonic movement on the sediment distribution of different tectonic units. The activity of Nankou-Sunhe Fault shows the strong-weak alternating pattern from the early Pleistocene to Holocene. In the early Pleistocene the activity intensity of Huangzhuang-Gaoliying Fault is stronger than Nankou-Sunhe Fault. After the early Pleistocene the activity intensity of Nankou-Sunhe Fault is stronger than Huangzhuang-Gaoliying Fault. The activity of the two faults tends to consistent till the Holocene.