自记钟的构适与维修

目前,地震前兆手段大多数是用自记钟作记录器。自记钟是一种较精密的仪器,所以在使用一段时间后,必须进行维修。现将自记钟的构造与维修介绍一下。一、构造     

虹吸触点式流量自记仪与模拟流量微机观测系统的研制

针对虹吸触点式流量自记仪在流量观测中存在的各种缺陷提出了解决的方法，介绍了模拟流量微机观测系统的结构、性能及特点。     

FSQ型自记水管倾斜仪观测干扰图象及其机理分析

0 前言 FSQ型自记水管倾斜仪的观测表明,地倾斜的变化与地震活动的增减有关,在中强地震前往往可以观测到倾斜的前兆异常变化。雅玛里克山1988年11月安装了FSQ型自记水管倾斜仪,并投入了正常的观测记录。两年来的观测实践表明,FSQ型自记水管倾斜仪具有稳定性好、易于标定、便于管理、记录连续、东西、南北两分量固体潮汐清晰、仪器所记录的参数物理意义明确等特点。从而填补了我国东经102°以西(除滇西外)4000000km~2余土地上没有高精度自记水管倾斜仪的空白。 然而在FSQ型自记水管倾斜仪观测中却存在着不容忽视的干扰因素。由于原始观测资料     

石油深井闭井连续自记测压方法及其在地震预报中的应用

本文着重介绍了石油深井闭井连续自记测压方法及其在地震预报中的应用。具体介绍了观测井条件、观测仪器及记录原理。通过对仪器及记录资料的分析,指出石油深井闭井连续自记测压方法与其它地震前兆观测方法相比具有许多优点。根据所记录到的较突出的短临异常变化,可以认为闭井测压是地震短临预报中较有发展前景的一种方法。     

光记录器的常见故碍及排除方法

金属水平摆倾斜仪、陶瓷偏角仪的光记录器中,用自记钟带动记录滚筒来实现观测资料的连续自记。它是台站中比较普遍使用的一种记录装置。由于它由机械部件所组成,运行中可能会出现一些机械故障,需要观测人员及时排除,这里就我们几年来使用的情况简单介绍一下可能遇到的故障及其排除方法,以供使用者维护时参考。     

乌鲁木齐妖魔山形变台FSQ型浮子自记水管倾斜仪投入试记

乌鲁木齐妖魔山(雅玛里克山)形变台的建设是新疆北天山重点监视区台网优化项目之一,按计划于1988年竣工并安装了高精度(10~(-9))的FSQ型浮子自记水管倾斜仪,自12月投入试记以来,运转正常,仪器记录清晰,己准确地记到固体潮汐。相信该仪器对我区的地震预报将起到一定的作用。     

柱坑深井水位的地震前兆信息

柱坑深井位于广东东北部的潮安-梅县北西向断裂的西端,观测孔深381.11米,孔口直径8.9厘米。水头高出地面4—5厘米。为不使其自流,在井口加高套管。自1978年7月开始,用HCJ-1自记水位计观测记录至现在。记录资料表明,仪器灵敏度可达0.5毫米,并能清晰地反映地球固体潮变化。     

易县地震台地形变模拟和数字化记录资料对比分析

用形变前兆台网及台站数据处理系统软件对易县地震台2002年度自记水管仪和伸缩仪的模拟记录和数字化记录资料进行处理,求得噪声水平、潮汐因子和误差,再计算出内在精度,从而在噪声水平和内在精度两个方面对模拟和数字化记录资料进行对比分析,从中发现数字化记录资料在内在精度和噪声水平两个方面均优于模拟记录资料.     

滇黔地区钻孔应变观测记震能力研究

使用2008~2011年MW6.0以上地震目录资料,统计滇黔地区贵阳、昭通、永胜、腾冲和丽江5个地震台的钻孔应变观测资料记录同震效应的情况,进行记震能力统计分析,给出了各台站钻孔应变观测的记震响应区域及记震能力图。根据地质构造及历史地震活动情况,对各观测台站记震能力进行了对比分析。结果表明,井孔位于稳定块体及历史地震活动少的台站记震能力强,记录的同震阶变现象少;反之则相反。通过记震能力分析可知,记震能力强的台站更有可能记录到更广范围的地震前兆异常现象。     

热电堆式海浪自记仪

引言研究海浪的物理性质时,必须取得波浪要素（周期、波高）的资料.对于表面波,由目测法、照相法及仪器自记法均可获得大量资料.对于海底压力波,则只能用自记法求得.一般可用电感式、电阻式、电位计式及热电堆式等自记仪来记录压力波.此地是介绍最后的一种形式.     

DOWN HOLE FLOWMETER ANALYSIS USING AN ASSOCIATED CALIPER LOG

Abstract From flowmeter interpretation studies using wells with no available caliper data has emerged information which is also pertinent to flowmeter analysis in conjunction with a caliper log. A simple method for interpreting flowmeter and caliper log pairs incorporating this insight has been developed. Location of constant-flow regions, inflow and outflow zones is done by manually comparing the shapes of the caliper and flowmeter logs. A flowrate log is then produced using quantitative volumetric flowrates calculated for several depths in the well. The log contains all the significant flow information without spurious noise and would be suitable for converting to an apparent hydraulic conductivity log.     

The Influence of Wellbore Inflow on Electromagnetic Borehole Flowmeter Measurements

This paper describes a combined field, laboratory, and numerical study of electromagnetic borehole flowmeter measurements acquired without the use of a packer or skirt to block bypass flow around the flowmeter. The most significant finding is that inflow through the wellbore screen changes the ratio of flow through the flowmeter to wellbore flow. Experiments reveal up to a factor of two differences in this ratio for conditions with and without inflow through the wellbore screen. Standard practice is to assume the ratio is constant. A numerical model has been developed to simulate the effect of inflow on the flowmeter. The model is formulated using momentum conservation within the borehole and around the flowmeter. The model is embedded in the MODFLOW-2000 ground water flow code.     

Evaluating the Use of In‐Well Heat Tracer Tests to Measure Borehole Flow Rates

Recent research has demonstrated the use of in‐well heat tracer tests monitored by a fiber optic distributed temperature sensing (DTS) system to characterize borehole flow conditions in open bedrock boreholes. However, the accuracy of borehole flow rates determined from in‐well heat tracer tests has not been evaluated. The purpose of the research presented here is to determine whether borehole flow rates obtained using DTS‐monitored in‐well heat tracer tests are reasonable, and to evaluate the range of flow rates measureable with this method. To accomplish this, borehole flow rates measured using in‐well heat tracer tests are compared to borehole flow rates measured in the same boreholes using an impeller or heat pulse flowmeter. A comparison of flow rates measured using in‐well heat tracer tests to flow rates measured with an impeller flowmeter under the same conditions showed good agreement. A comparison of in‐well heat tracer test flow rate measurements to previously‐collected heat pulse flowmeter measurements indicates that the heat tracer test results produced borehole flow rates and flow profiles similar to those measured with the heat pulse flowmeter. The results of this study indicate that borehole flow rates determined from DTS‐monitored in‐well heat tracer tests are reasonable estimates of actual borehole flow rates. In addition, the range of borehole flow rates measurable by in‐well heat tracer tests spans from less than 10^?1 m/min to approximately 10¹ m/min, overlapping the ranges typically measurable with an impeller flowmeter or a heat pulse flowmeter, making in‐well heat tracer testing a versatile borehole flow logging tool.     

Accuracy of Flowmeters Measuring Horizontal Groundwater Flow in an Unconsolidated Aquifer Simulator

Borehole flowmeters that measure horizontal flow velocity and direction of groundwater flow are being increasingly applied to a wide variety of environmental problems. This study was carried out to evaluate the measurement accuracy of several types of flowmeters in an unconsolidated aquifer simulator. Flowmeter response to hydraulic gradient, aquifer properties, and well‐screen construction was measured during 2003 and 2005 at the U.S. Geological Survey Hydrologic Instrumentation Facility in Bay St. Louis, Mississippi. The flowmeters tested included a commercially available heat‐pulse flowmeter, an acoustic Doppler flowmeter, a scanning colloidal borescope flowmeter, and a fluid‐conductivity logging system. Results of the study indicated that at least one flowmeter was capable of measuring borehole flow velocity and direction in most simulated conditions. The mean error in direction measurements ranged from 15.1° to 23.5° and the directional accuracy of all tested flowmeters improved with increasing hydraulic gradient. The range of Darcy velocities examined in this study ranged 4.3 to 155 ft/d. For many plots comparing the simulated and measured Darcy velocity, the squared correlation coefficient (r²) exceeded 0.92. The accuracy of velocity measurements varied with well construction and velocity magnitude. The use of horizontal flowmeters in environmental studies appears promising but applications may require more than one type of flowmeter to span the range of conditions encountered in the field. Interpreting flowmeter data from field settings may be complicated by geologic heterogeneity, preferential flow, vertical flow, constricted screen openings, and nonoptimal screen orientation.     

Permeability profiles in granular aquifers using flowmeters in direct-push wells

Numerical hydrogeological models should ideally be based on the spatial distribution of hydraulic conductivity (K), a property rarely defined on the basis of sufficient data due to the lack of efficient characterization methods. Electromagnetic borehole flowmeter measurements during pumping in uncased wells can effectively provide a continuous vertical distribution of K in consolidated rocks. However, relatively few studies have used the flowmeter in screened wells penetrating unconsolidated aquifers, and tests conducted in gravel-packed wells have shown that flowmeter data may yield misleading results. This paper describes the practical application of flowmeter profiles in direct-push wells to measure K and delineate hydrofacies in heterogeneous unconsolidated aquifers having low-to-moderate K (10(-6) to 10(-4) m/s). The effect of direct-push well installation on K measurements in unconsolidated deposits is first assessed based on the previous work indicating that such installations minimize disturbance to the aquifer fabric. The installation and development of long-screen wells are then used in a case study validating K profiles from flowmeter tests at high-resolution intervals (15 cm) with K profiles derived from multilevel slug tests between packers at identical intervals. For 119 intervals tested in five different wells, the difference in log K values obtained from the two methods is consistently below 10%. Finally, a graphical approach to the interpretation of flowmeter profiles is proposed to delineate intervals corresponding to distinct hydrofacies, thus providing a method whereby both the scale and magnitude of K contrasts in heterogeneous unconsolidated aquifers may be represented.     

The Electromagnetic Borehole Flowmeter: Description and Application

Borehole flowmeters are downhole tools that measure axial flow in a well or borehole. Desirable flowmeter characteristics include low detection limit, a wide range of operation, accuracy, durability, reliable performance, and a small diameter and length. The recently developed electromagnetic (F.M) flowmeter has these trails. The first portion of this paper presents the MM flowmeter design, provides laboratory calibration data, and compares the performance characteristics of MM flowmeters 10 those of impeller and thermal pulse flowmeters. The second portion of the paper discusses applications of the MM flowmeter.     

Estimation of water velocities in boreholes using a new passive flowmeter

Abstract

Preferential flow pathways in a fractured aquifer may yield abrupt reductions of the water velocity in a well. We propose a new device for measuring low (5–13 cm d^-1) velocities in wells originating from fractures at different depths. The presented flowmeter has been applied in a well in the Bari (southern Italy) fractured aquifer. In the same well, the horizontal flowmeter velocity (9.6 cm d^-1) at 0.5 m depth was compared with velocity (8 cm d^-1) derived from a field tracer test, providing a value 16.5% higher. Moreover, the flowmeter measurements at 1.5 m depth gave a horizontal velocity of 7.2 cm d^-1, which is 11% less than water flow velocity estimated from the field test. The new flowmeter implements the tracer point-dilution method in a plastic (PVC) pipe by causing the water flow to pass through an artificial filter. Laboratory calibration tests have confirmed the good performance of the proposed flowmeter technique, even for water flow up to 300 cm d^-1. The flowmeter was sensitive to 0.1 cm d^-1, with a detection limit of 1.5 cm d^-1, i.e. half the measurable flow velocity of existing flowmeters in wells.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi     

Characterization of High-K Pathways by Borehole Flowmeter and Tracer Tests

This paper reviews different borehole flowmeter analysis methods and evaluates their applicability to a test site composed of fluvial deposits. Results from tracer and aquifer tests indicate that the aquifer is highly heterogeneous and that low-K skin effects exist at the wells. Borehole flowmeter tests were performed at 37 wells. An appropriate method for calculating borehole flowmeter K values was developed based on results from multiwell pumping tests, single-well pumping tests, and slug tests. The flowmeter data produced 881 K values. The trends and the magnitude of the K values are consistent with results from geologic investigations, recirculating tracer tests, and large-scale multiwell pumping tests. The field tests illustrate that high-K deposits can significantly affect ground-water flows in some heterogeneous fluvial aquifers.     

Tidal effects on variations of fresh–saltwater interface and groundwater flow in a multilayered coastal aquifer on a volcanic island (Jeju Island, Korea)

We conducted various field studies at the seawater intrusion monitoring wells located in the eastern part of Jeju Island, Korea, to observe the tidal effect on groundwater–seawater flow in the coastal aquifer. Studies included monitoring the fluctuations of groundwater and tide levels, electrical and temperature logging, and 2-D heat-pulse flowmeter tests. According to time-series analysis, tidal effects on groundwater level reached up to 3 km inland from the coastline. Water-level variation was more sensitive to tidal fluctuations near the coast, and more related to rainfall toward inland areas. Temporal and spatial variations in the shape and location of the freshwater–saltwater interface were analyzed using data from nine monitoring wells. The results indicated that the interface toe is located at a distance of 6–8 km from the coastline and its location was related to geological layers present. Long-term seasonal variations revealed no major changes in the interface; minor variations were due to moving boundary conditions induced by tidal fluctuations. Using the two-dimensional heat-pulse flowmeter, groundwater flow directions and velocities at four tidal stages were measured on three monitoring wells drilled into the multilayered aquifers. This direct measurement enabled us to relate the differences of flow velocities and directions with geology and tidal fluctuations. Combining the results of EC logging and flowmeter tests, we found a zone where freshwater and saltwater moved alternately in opposite directions, as influenced by the tidal fluctuations. Integrating various physical logging and flowmeter data with water-level fluctuations improved our understanding of the behavior of fresh and seawater flow in the coastal aquifers.     

Cross-borehole flowmeter tests for transient heads in heterogeneous aquifers

Cross-borehole flowmeter tests have been proposed as an efficient method to investigate preferential flowpaths in heterogeneous aquifers, which is a major task in the characterization of fractured aquifers. Cross-borehole flowmeter tests are based on the idea that changing the pumping conditions in a given aquifer will modify the hydraulic head distribution in large-scale flowpaths, producing measurable changes in the vertical flow profiles in observation boreholes. However, inversion of flow measurements to derive flowpath geometry and connectivity and to characterize their hydraulic properties is still a subject of research. In this study, we propose a framework for cross-borehole flowmeter test interpretation that is based on a two-scale conceptual model: discrete fractures at the borehole scale and zones of interconnected fractures at the aquifer scale. We propose that the two problems may be solved independently. The first inverse problem consists of estimating the hydraulic head variations that drive the transient borehole flow observed in the cross-borehole flowmeter experiments. The second inverse problem is related to estimating the geometry and hydraulic properties of large-scale flowpaths in the region between pumping and observation wells that are compatible with the head variations deduced from the first problem. To solve the borehole-scale problem, we treat the transient flow data as a series of quasi-steady flow conditions and solve for the hydraulic head changes in individual fractures required to produce these data. The consistency of the method is verified using field experiments performed in a fractured-rock aquifer.