充液井中多极声源的辐射效率

利用反射声场探测井外地质构造的声波远探测方法已逐渐成为石油测井的一门重要应用技术.在远探测测井中声源常采用单极、偶极和四极等.为了考察各种声学辐射器的辐射性能,本文从辐射声场和井孔声场的能流密度出发,提出了一种利用辐射器向井外辐射的能量与沿井筒传播的能量比的大小来评价其辐射效率的方法,考察了不同声源激发的沿井传播的导波能流、地层辐射波能流及声源辐射效率随频率的变化规律.计算结果表明:不同声源的辐射效率和优势激发频段各不相同.单极声源在低频下的辐射效率很低,因为此时声源激发的能量几乎全部被斯通利波带走,相比之下,偶极声源在低频时的辐射效率远大于单极声源.本文的结果说明了偶极声源作为低频远探测声源要优于单极声源.     

井中磁源瞬变电磁响应特征研究

井中瞬变电磁波勘探是一个全空间地球物理场问题.采用Gaver-Stehfest逆拉氏变换方法,正演计算了瞬变信号激励下接收线圈上的电磁场响应.分析了包含井眼泥浆、套管、水泥环和地层的轴对称多层介质模型的电磁场响应特征,考察了各层介质参数对井中瞬变电磁响应的影响.不同电导率井眼泥浆的电磁场响应衰减曲线表明,井眼泥浆电导率的变化对井中瞬变电磁响应的影响极小.不同套管几何参数的电磁响应数值模拟结果显示,套管内径变化对电磁响应有较大影响;在套管厚度变化的端点处,电磁响应存在明显异常.通过对不同套管磁导率电磁响应特征的讨论,认为套管磁导率参数对电磁响应有重要影响,套管相对磁导率越高,电磁波信号越难穿过套管,响应信号幅度越低.最后,对不同水泥环参数的电磁场响应进行了数值模拟,发现对于低导地层,低阻水泥环会产生较大的测量误差;而对高导地层,水泥环厚度参数对响应信号影响可忽略不计.     

The strain seismograms of P- and S-waves of a local event recorded by four-gauge borehole strainmeter

At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters(FGBS) are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.     

藏北地区钻孔大地热流值测量

本文利用藏北地区三口天然气水合物钻孔测温数据,在分析样品热导率测试结果基础上,计算了藏北地区的热流值.对于样品热导率值,首先根据样品孔隙度对实验室测试结果进行了饱水校正,计算热流时采用的是对应井段的岩石热导率饱水校正值的厚度加权平均值.地温梯度以三口钻孔48 h的测温数据为基础,回归三口井的地温梯度,计算时去除了浅部受地表温度和冻土带对温度影响的数值.A钻孔地温梯度分为200~438 m和438~882 m两段回归,分段热流的加权平均值作为钻孔热流值,计算结果为42.7 mW·m^-2;B钻孔和C钻孔回归地温梯度时未分段,热流计算结果分别为58.3 mW·m^-2、70 mW·m^-2.综合分析认为,岩石圈断裂、地幔上涌、碰撞造山过程中的剪切生热等因素可能造成了班公湖—怒江缝合带以南热流值较高,而北部羌塘地块热流值相对较低.

     

利用井中偶极声源远场辐射特性的远探测测井

远探测声波测井技术近年来的一个重要进展是利用偶极声波探测仪器来发射和接收地层深部的反射信号.本文论述了这种偶极声波远探测技术的基本原理和方法,并结合数值模拟计算验证了该方法的可行性及灵敏度.具体来说,井中偶极声源向地层深部辐射出纵波、SH和SV型横波,其中SH型横波具有很宽的辐射覆盖及较高的反射灵敏度,是偶极横波远探测的重要依据.在慢速地层中,偶极辐射的纵波具有振幅强、灵敏度高的特征,也可以用于远探测测井.偶极远探测的另一个重要特征是其对反射体的方位灵敏度,这是由于声源为指向性发声的结果.采用四分量的数据采集方式便可以确定反射体走向的方位.在理论分析的基础上,我们用实际例子说明偶极声波远探测的重要特征及其有效性.     

利用井中偶极声源远场辐射特性的远探测测井

远探测声波测井技术近年来的一个重要进展是利用偶极声波探测仪器来发射和接收地层深部的反射信号.本文论述了这种偶极声波远探测技术的基本原理和方法,并结合数值模拟计算验证了该方法的可行性及灵敏度.具体来说,井中偶极声源向地层深部辐射出纵波、SH和SV型横波,其中SH型横波具有很宽的辐射覆盖及较高的反射灵敏度,是偶极横波远探测...     

仪器标定格值变化对钻孔应变观测数据的影响

以巴南地震台钻孔应变某一时段观测资料异常变化为例,指出观测仪器元件标定格值是影响钻孔应变观测数据的重要参数,与固体潮汐幅度成反比例关系,且格值变化也可能是改变钻孔应变趋势形态的一种因素。文中分析格值与应变观测数据之间的物理机制,校正恢复异常时段观测曲线,为钻孔应变异常干扰识别工作提供参考。     

钻孔环境在钻孔地形变观测中的作用

正式提出了钻孔环境问题,它对于钻孔形变仪器的安装顺利与否,资料质量好坏,资料的使用价值等,有着重大的影响。对钻孔环境的内涵作了初步的讨论,如钻孔的倾斜,钻孔的畸变,钻孔穿过破碎带和裂隙及钻孔的历史背景等。     

深井宽频带地震计的研制

深井地震观测可以排除地面噪声干扰的影响,提高观测的信噪比,应用前景广泛。文中介绍基于DSP的深井宽频带地震计,总体介绍其特点、组成、原理,并对某些关键问题进行阐述,说明各部分的具体实现方案,并研制初步样机。     

温度对甚宽频地震计性能的影响

以甚宽频地震计BBVS120为研究对象,通过温度实验测试,研究温度对甚宽频地震计性能影响。结合分析关键元件材料的温度特性,讨论温度对甚宽频地震计灵敏度、幅频特性影响的原因,科学评价观测仪器的温度效应。     

The marine controlled source electromagnetic response of a steel borehole casing: applications for the NEPTUNE Canada gas hydrate observatory

Gas hydrates are a potential energy resource, a possible factor in climate change and an exploration geohazard. The University of Toronto has deployed a permanent seafloor time‐domain controlled source electromagnetic (CSEM) system offshore Vancouver Island, within the framework of the NEPTUNE Canada underwater cabled observatory. Hydrates are known to be present in the area and due to their electrically resistive nature can be monitored by 5 permanent electric field receivers. However, two cased boreholes may be drilled near the CSEM site in the near future. To understand any potential distortions of the electric fields due to the metal, we model the marine electromagnetic response of a conductive steel borehole casing. First, we consider the commonly used canonical model consisting of a 100 Ωm, 100 m thick resistive hydrocarbon layer embedded at a depth of 1000 m in a 1 Ωm conductive host medium, with the addition of a typical steel production casing extending from the seafloor to the resistive zone. Results show that in both the frequency and time domains the distortion produced by the casing occurs at smaller transmitter‐receiver offsets than the offsets required to detect the resistive layer. Second, we consider the experimentally determined model of the offshore Vancouver Island hydrate zone, consisting of a 5.5 Ωm, 36 m thick hydrate layer overlying a 0.7 Ωm sedimentary half‐space, with the addition of two borehole casings extending 300 m into the seafloor. In this case, results show that the distortion produced by casings located within a 100 m safety zone of the CSEM system will be measured at 4 of the 5 receivers. We conclude that the boreholes must be positioned at least 200 m away from the CSEM array so as to minimize the effects of the casings.     

The influence of water retention curve hysteresis on the stability of unsaturated soil slopes

Hysteresis is a common feature exhibited in hydraulic properties of an unsaturated soil. The movement of wetting front and the hysteresis effect are important factors which impact the shear strength of the unsaturated soil and the mechanics of shallow landslides. These failures are mainly triggered by the deepening of the wetting front accompanied by a decrease in matric suction induced by infiltration. This research establishes a method for determining a stability analysis of unsaturated infinite soil slopes, integrating the influence of infiltration and the water retention curve hysteresis. Furthermore, the present stability analysis method including the infiltration model and the advanced Mohr–Coulomb failure criterion calculates the variations of the safety factor (FS) in accordance with different slope angle, depth and hydrological processes. The experimentally measured data on the effect of hysteresis are also carried out for comparison. Numerical analyses, employing both wetting and drying hydraulic behaviour of unsaturated soil, are performed to study the difference in soil‐water content as observed in the experiments. The simulating approximations also fully responded to the experimental data of sand box. The results suggest that the hysteresis behaviour affect the distribution of soil‐water content within the slope indeed. The hysteresis made the FS values a remarkable recovery during the period of non‐rainfall in a rainfall event. The appropriate hydraulic properties of soil (i.e. wetting or drying) should be used in accordance with the processes that unsaturated soil actually experience. This method will enable us to acquire more accurate matric suction head and the unsaturated soil‐shear strength as it changes with the hysteretic flow, in order to calculate into the stability analysis of shallow landslides. An advanced understanding of the process mechanism afforded by this method is critical to realizing a reliable and appropriate design for slope stabilization. It also offers some immediate reference information to the disaster reduction department of the government. Copyright © 2011 John Wiley & Sons, Ltd.     

The influence of topography and approach angles on local deflections of airflow within a coastal blowout

The spatial variability of air flow through complex topography is an important, but not fully understood, component of dune development and dynamics. This study examines the spatial variability of the wind field in a linear blowout in coastal dunes at Jockey's Ridge State Park, on the Outer Banks of North Carolina. A spatial array of single‐height anemometers and wind vanes were placed within the blowout. Topography exerted a significant steering effect when onshore winds approached from directions within 50° of the blowout axis. Under those conditions wind flow in the blowout aligned to the axis regardless of approach angle, maximizing the potential for erosion and transport in the trough. In other locations aspect variations caused deflection both proportional and disproportional to changes in the approaching wind. When prevailing winds approached from directions more oblique than 50° to the blowout axis, topographic steering through the blowout trough was reduced and secondary flow generated by flow separation over the trough became more prominent. During those approach angles, wind directions and speeds within the upper blowout trough became erratic as vortices and turbulence dominated the flow, minimizing transport potential. The changing characteristics of airflow in the blowout relative to differing approach angles has implications on dune development and variations in transport potential under changing conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

敦化地震台2010年9月钻孔应变观测曲线异常分析

对敦化地震台2010年9月10日起YRY-4钻孔应变观测曲线异常进行分析,排除干扰的可能性,确认为敦化地区地质活动的真实反映.分析认为,该异常为2011年3月11日13:46:21时日本本州东海岸附近海域9.0级地震孕震过程中,太平洋板块和欧亚板块挤撞的真实反映.     

The effect of climate-change-related heat waves on mortality in Spain: uncertainties in health on a local scale

Different epidemiological studies have shown that high temperatures are directly related to mortality, furthermore many studies on the effects of climate change on future mortality are being conducted. The objective of this study is to estimate the effect of extreme hot temperatures on daily mortality in Zaragoza (Spain) from 2014 to 2021, utilising various climate-change scenarios. The relationship between temperature and mortality is defined by the concepts of heat wave, threshold temperature and the relative risk of daily deaths according to extreme temperatures in 1987–2006 period. The effect on future mortality is projected by estimating deaths attributable to extreme temperatures in 2014–2021. This estimation was calculated utilising exposure–response functions for three scenarios (A1B, A2 and B1) from the ECHAM5 general circulation model after applying a statistical downscaling technique. Because this study considers the effect of rising temperatures from a health perspective, minimising uncertainty was added to the numerical values obtained from the projected future relation between temperature and mortality. The results shows that expected mortality in Zaragoza will increase by 0.4 % for the period 2014–2021, an excess that can be directly attributed to extreme temperatures. This effect is expected to increase in the 2040s and 2050s until the end of the twenty first century because of a predicted increase in temperatures over this period, with special emphasis on the need to continue studying this line of inquiry and local studies as which arises. Finally, this study will luckily be used to create prevention plans for minimising the effect on health of the high temperatures.     

The influence of pool length on local turbulence production and energy slope: a flume experiment

The in?uence of pool length on the strength of turbulence generated by vortex shedding was investigated in a 6 m long recirculating ?ume. The experiment utilized a 38% constriction of ?ow and an average channel‐bed slope of 0·007. The base geometry for the intermediate‐length pool experiment originated from a highly simpli?ed, 0·10 scale model of a forced pool from North Saint Vrain Creek, Colorado. Discharge in the ?ume was 31·6 l/s, which corresponds to a discharge in the prototype channel of 10 m³/s. Three shorter and four longer pool lengths also were created with a ?xed bed to determine changes in turbulence intensities and energy slope with pool elongation. Three‐dimensional velocities were measured with an acoustic Doppler velocimeter at 31–40 different 0·6‐depth and near‐bed locations downstream of the rectangular constriction. The average velocity and root mean square (RMS) of the absolute magnitude of velocity at both depths are signi?cantly related to the distance from the constriction in most pool locations downstream of the constriction. In many locations, pool elongation results in a non‐linear change in turbulence intensities and average velocity. Based on the overall ?ow pattern, the strongest turbulence occurs in the center of the pool along the shear zone between the jet and recirculating eddy. The lateral location of this shear zone is sensitive to changes in pool length. Energy slope also was sensitive to pool length due to a combination of greater length of the pool and greater head loss with shorter pools. The results indicate some form of hydraulic optimization is possible with pools adjusting their length to adjust the location and strength of turbulent intensities in the center of pools, and lower their rate of energy dissipation. Copyright © 2004 John Wiley & Sons, Ltd.     

光缆布设方式对DAS主、被动源记录的影响

近年来分布式光纤声波传感器在近地表结构的主、被动源地震成像中得到了广泛应用,前人研究发现不同布设方式光缆记录的数据质量差别较大,有可能影响成像结果.因此本文针对光缆布设方式对分布式光纤声波传感器记录的主、被动源数据的影响开展了观测实验,设计了水泥胶结、路面摆放、架空三种布设方式模拟实际情况中的光缆,开展了主、被动源信号观测.基于光缆记录的被动源信号计算噪声互相关函数,采用多道面波分析法测量不同光缆的相速度频散曲线,并对比三种布设方式的光缆记录的主动源信号波形与到时等信息.结果表明水泥胶结和路面摆放布设方式可以提供质量较好且一致的主、被动源数据,但是悬空光缆的信号质量与频谱受到光缆自振的影响. 利用滤波去除光缆自振影响后,其频散曲线与水泥胶结和地面摆放光缆提取的频散曲线误差在5 m·s^-1以内. 通过相应优化手段后,三种布设方式的光缆记录的主、被动源数据都可以用于面波和体波走时成像,而主动源信号波形信息差异较大,难以直接用于相关成像研究,有待开展进一步工作.

     

Vertical groundwater flux estimation from borehole temperature profiles by a numerical model,RFLUX

We developed a numerical model, RFLUX, which uses the heat tracer method for vertical groundwater flux estimation, and applied it to the Leizhou Peninsula, South China, to provide information to inform local groundwater resource utilization and management. The temperature–depth (TD) profiles of 24 boreholes, along with the observed ground surface temperature (GST) and surface air temperature (SAT) series in recent decades, were collected in this area. Underground TD data demonstrated the capacity to identify groundwater flow patterns, and local GST and SAT data demonstrated a strong correlation with each other over monthly, seasonal, and annual scales. In the RFLUX model, the average GST and SAT series were applied as an upper boundary condition, and a nonlinear initial condition was set using an analytical solution from the literature. The model results of selected TD profiles demonstrated that the annual vertical groundwater flux was about 0.15 m a^?1, which tended to be overestimated if a linear initial condition was used. This model can be easily applied with minor modifications, considering its clear purpose and simplicity.     

长春地区地表温度日变、年变对地温测量的影响

通过实地观测试验,并采用傅里叶分析法进行理论分析,来研究长春地区地表温度日变、年变对地温测量的影响规律及影响深度,为在长春地区利用浅层地温测量方法研究地质问题提供重要参数信息.地温变化幅度随深度作指数衰减,衰减系数与地表温度周期、热扩散率有关.     

Long-term temperature monitoring in a borehole drilled into the Nojima Fault, southwest Japan

Abstract Long-term monitoring of temperature distribution in an active fault zone was carried out using the optical fiber temperature-sensing technique. An optical fiber cable was installed in a borehole drilled into the Nojima Fault in Awaji Island, south-west Japan, and the temperature profile to a depth of 1460 m had been measured for 2.5 years (July 1997–January 2000). Although the obtained temperature records showed small temporal variations due to drifts of the measurement system all along the cable, local temperature anomalies were detected at two depths. One at around 80 m seems to correspond to a fracture zone and may be attributed to groundwater flow in the fracture zone. This anomaly had been stable throughout the monitoring period, whereas the other anomaly at around 500 m was a transient one. The water level in the borehole could be estimated from the diurnal temperature variations in the uppermost part of the borehole and may provide information on the hydrological characteristics of the fault zone, which is connected to the borehole through perforations on the casing pipe. Except for these minor variations, the temperature profile had been very stable for 2.5 years. The conductive heat flow calculated from this profile and the thermal conductivity measured on core samples increases with depth, probably resulting from errors in thermal conductivity due to sampling problems and/or from advective heat transfer by regional groundwater flow. Assuming that the middle part of the borehole (less fractured granite layer) is least affected by these factors, heat flow at this site is estimated to be approximately 70 mW/m².