Evolution of the stress and strain fields in the Eastern Cordillera,Colombia     

《Journal of Structural Geology》2014

This work integrates stress data from Global Positioning System measurements and earthquake focal mechanism solutions, with new borehole breakout and natural fracture system data to better understand the complex interactions between the major tectonic plates in northwestern South America and to examine how the stress regime in the Eastern Cordillera and the Llanos foothills in Colombia has evolved through time. The dataset was used to generate an integrated stress map of the northern Andes and to propose a model for stress evolution in the Eastern Cordillera. In the Cordillera, the primary present-day maximum principal stress direction is WNW–ESE to NW–SE, and is in the direction of maximum shortening in the mountain range. There is also a secondary maximum principal stress direction that is E–W to ENE–WSW, which is associated with the northeastward “escape” of the North Andean block, relative to stable South America. In the Cupiagua hydrocarbon field, located in the Llanos foothills, the dominant NNE–SSW fractures are produced by the Panama arc–North Andes collision and range-normal compression. However, less well developed asymmetrical fractures oriented E–W to WSW–ENE and NNW–SSE are also present, and may be related to pre-folding stresses in the foreland basin of the Central Cordillera or to present-day shear associated with the northeastward “escape” of the north Andean block. Our study results suggest that an important driver for orogenic deformation and changes in the stress field at obliquely convergent subduction zone boundaries is the arrival of thickened crust, such as island arcs and aseismic ridges, at the trench.  相似文献   

Numerical simulation of deep-hole resistivity anomaly caused by drilling construction in Xinfengjiang geoelectric station     

Xing Yan  Zhihui Deng  Jiping Liu  Shishan Ye  Zhiqun Chen  Tianren Zhong 《地震研究进展（英文）》2022,2(3):100139

The Xinfengjiang reservoir in Guangdong Province, is one of the large reservoirs that have triggered earthquakes of magnitude greater than 6. Numerous earthquakes have occurred since the impoundment of the reservoir, making it one of the most active seismic zones in south China. In 2015, a set of deep-hole resistivity anomalies was observed in the Heping geoelectric station in Dongyuan county, located near the Xinfengjiang reservoir. After a field investigation, we found that a planned well drilling construction of new measuring channels was being carried out during that corresponding period of time. After careful comparison and analysis on the basis of the collected raw data, we had a reason to believe that drilling construction, rather than the inducement of the Xinfengjiang reservoir, was the main culprit for those unusual georesistivity values. So as to verify the above conjecture, we constructed a series of 3D finite element models based on the geological and hydrological information around Heping station and analyzed the drilling disturbances, respectively. Some significant conclusions were finally drawn according to the precise numerical simulation. This study gives a good example by combining numerical simulation with engineering practice as a way to understand the root cause of georesistivity anomalies in reality.  相似文献   

声学井下电视在刚果（金）KOLWEZI铜矿矿区中的应用     

方良平 《地下水》2015,(2)

声学井下电视具有不受钻井液限制、图像分辨率高、方位确定准确的特点,特别适合于确定岩石的走向、倾向、倾角、裂隙和破碎软弱发育情况,从而可以更好的统计出岩体的优势结构面,为矿区工程地质边坡稳定性评价提供重要依据。通过介绍声学井下电视的设备及操作过程,软件处理和对 KOLWEZI矿区 GK10号钻孔岩体的井下电视结果进行分析,总结井下电视数据处理方法和实验结果与评价矿区边坡稳定性的重要关系。  相似文献   

Numerical Simulation of 3D Borehole‐to‐Surface Electrical Method     

Xiong Zhitao  Tang Xingong  Li Dandan  Zhao Chunyan 《《地质学报》英文版》2019,93(Z1):340-341

The anomaly response characteristics of the vertical line‐source 3D borehole‐to‐surface model are simulated by an adaptive finite element method. The calculation shows that the anomaly in the radial direction is pressed and the closer to the source, the more pronounced, the anomaly is stretched in the direction perpendicular to the radius. Adding a B pole in the Y direction can offset the effect of stretching to some extent. The anomaly that is closer to the source of the profile is clearer than the anomaly that is far from the source. The research results are of great significance for guiding the practical application of the borehole‐to‐surface electrical method.  相似文献   

Assessing potential land suitable for surface irrigation using groundwater in Ethiopia     

《Applied geography (Sevenoaks, England)》2017

Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized. This study evaluates suitability of lands for irrigation using groundwater in Ethiopia using GIS-based Multi-Criteria Evaluation (MCE) techniques in order to enhance the country's agricultural industry. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope), climate (rainfall and evapotranspiration), and market access (proximity to roads and access to market). These factors were weighted using a pair-wise comparison matrix, then reclassified and overlaid to identify suitable areas for groundwater irrigation using a 1-km grid. Groundwater data from the British Geological Survey were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crops. Results indicated that more than 6 million ha of land are suitable for irrigation in Ethiopia. A large portion of the irrigable land is located in the Abbay, Rift Valley, Omo Ghibe, and Awash River basins. These basins have access to shallow groundwater (i.e., depth of groundwater less than 20 m from the surface) making it easier to extract. The comparison between available groundwater and total crop water requirements indicate that groundwater alone may not be sufficient to supply all suitable land. The study estimates that only 8% of the suitable land can be irrigated with the available shallow groundwater. However, groundwater is a viable option for supplementing surface water resources for irrigation in several basins in the country.  相似文献   

Probing fault zone heterogeneity on the Nojima fault: Constraints from zircon fission-track analysis of borehole samples   总被引：2，自引：0，他引：2  

Takahiro Tagami  Masaki Murakami 《Tectonophysics》2007,443(3-4):139

Fission-track (FT) thermochronologic analysis was performed on zircon separates from rocks in and around the Nojima fault, which was activated during the 1995 Kobe earthquake. Samples were collected from the University Group 500 m (UG-500) borehole and nearby outcrops. FT lengths in zircons from localities > 25 m away from the fault plane as well as one 0.1 m away from the fault in the footwall are characterized by concordant mean values of  10–11 μm and unimodal distributions with negative skewness, which showed no signs of appreciable reduction in FT length. In contrast, those adjacent (< 3 m) to the fault at depths on the hanging wall side showed significantly reduced mean track lengths of  6–8 μm and distributions having a peak around 6–7 μm with rather positive skewness. The former pattern is interpreted to reflect cooling through the zircon partial annealing zone (ZPAZ), without later, partial thermal overprints. The latter indicates substantial track shortening due probably to secondary heating by a thermal event(s) that locally perturbed the geothermal structure. Modeled zircon FT length and age data of partially annealed samples from the UG-500 borehole revealed a cooling episode in the ZPAZ that started at  4 Ma within  3 m from the fault plane, whereas those from the Geological Survey of Japan 750 m borehole record cooling started at  31–38 Ma within  25 m from the fault. On the basis of one-dimensional heat conduction modeling as well as the consistency between the degree of FT annealing and the degree of deformation/alteration of borehole rocks, these cooling ages in both boreholes are interpreted as consequences of ancient thermal overprints by heat transfer or dispersion via fluids in the fault zone. Together with the zircon FT data of a pseudotachylyte layer recently analyzed, it is suggested that the present Nojima fault system was reactivated in the Middle Quaternary from an ancient fault initiated at  56 Ma at mid-crustal depths. Also shown is a temporal/spatial variation in terms of the thermal anomalies recorded in the fault rocks, implying heterogeneity of hot fluid flows in the fault zone.  相似文献   

井下地震计的P波接收函数正演计算及其稳定性研究——以首都圈地区为例          下载免费PDF全文

郑德高  倪四道  杨卓欣  刘志 《地球物理学报》2018,61(10):3964-3979

井下地震计波形记录的P波垂向分量存在频谱极小（spectrum null）现象,导致接收函数的结果不稳定.本文以首都圈地区为例,基于平面波入射的传播矩阵理论,发展了用于计算井下地震计的接收函数正演方法.在此基础上,分析了井下地震计波形垂向分量频谱极小现象,研究其对接收函数稳定性的影响.结果表明,井下地震计波形记录垂向分量的频谱极小开始出现的频率和地震计的埋深相关.该现象可造成反卷积提取的接收函数不稳定,且不稳定情况出现在频谱极小附近的频段,可通过选择合适的高斯因子压制其对接收函数的影响.  相似文献   

Feasibility of borehole ambient noise interferometry for permanent reservoir monitoring          下载免费PDF全文

M. Behm 《Geophysical Prospecting》2017,65(2):563-580

The analysis of seismic ambient noise acquired during temporary or permanent microseismic monitoring campaigns (e.g., improved/enhanced oil recovery monitoring, surveillance of induced seismicity) is potentially well suited for time‐lapse studies based on seismic interferometry. No additional data acquisition required, ambient noise processing can be automatized to a high degree, and seismic interferometry is very sensitive to small medium changes. Thus there is an opportunity for detection and monitoring of velocity variations in a reservoir at negligible additional cost and effort. Data and results are presented from an ambient noise interferometry study applied to two wells in a producing oil field in Romania. Borehole microseismic monitoring on three component geophones was performed for four weeks, concurrent with a water‐flooding phase for improved oil recovery from a reservoir in ca. 1 km depth. Both low‐frequency (2 Hz–50 Hz) P‐ and S‐waves propagating through the vertical borehole arrays were reconstructed from ambient noise by the virtual source method. The obtained interferograms clearly indicate an origin of the ambient seismic energy from above the arrays, thus suggesting surface activities as sources. It is shown that ambient noise from time periods as short as 30 seconds is sufficient to obtain robust interferograms. Sonic log data confirm that the vertical and horizontal components comprise first arrivals of P‐wave and S‐waves, respectively. The consistency and high quality of the interferograms throughout the entire observation period further indicate that the high‐frequency part (up to 100 Hz) represents the scattered wave field. The temporal variation of apparent velocities based on first‐arrival times partly correlates with the water injection rate and occurrence of microseismic events. It is concluded that borehole ambient noise interferometry in production settings is a potentially useful method for permanent reservoir monitoring due to its high sensitivity and robustness.  相似文献   

鄂尔多斯盆地北部东胜地区侏罗系—白垩系钻孔数据库与三维地质模型          下载免费PDF全文

张天福  张云  程先钰  孙立新  程银行  周小希  王少轶  马海林  鲁超 《中国地质》2020,47(S1):220-230

随着砂岩型铀矿找矿工作的进一步开展,其对以往钻孔资料集成应用的需求尤为迫切。在煤田钻孔资料“二次开发利用”和“煤铀兼探”新方法、新思路的指导下,通过采集东胜地区钻孔资料属性数据,按照统一的标准和要求,将煤田、铀矿等类型的重要钻孔资料,通过整理、扫描、数据类型转换、录入和集成,建成了东胜地区侏罗系—白垩系综合钻孔数据库,实现了对多源钻孔数据的统一管理。该数据库共包含3个Access数据库和相应的成果图件。每个Access数据库均包含钻孔基本信息表、综合柱状分层表、岩性描述分层表、地层名称及代号表、地层颜色表、测井曲线数据表、测井曲线配置表和钻孔弯曲度测量数据表等8张数据表,分别详细记录了地质编录岩性信息、地层分层信息、岩石颜色信息、测井曲线信息、水文分层信息、钻孔样品采样信息、弯曲度测量信息等。通过应用实践,该钻孔数据库成果可实现连井剖面、含煤含铀目的层的顶底板标高、地层等厚图、砂体等厚图及含砂率图等重要基础地质图件的快速生成,从而提高数据的使用效率并为铀矿勘查及研究工作提供重要数据基础。  相似文献   

Reservoir architecture and heterogeneity distribution in floodplain sandstones: Key features in outcrop,core and wireline logs     

Luis Miguel Yeste  Augusto N. Varela  César Viseras  Neil D. Mcdougall  Fernando García-García 《Sedimentology》2020,67(7):3355-3388

  相似文献