Correlation analysis between fault frequency and service time of underground fluid instruments

In this paper, we make a statistical analysis of the fault information of the underground fluid instruments of 12 models in China from January 2021 to May 2022 based on the Pearson correlation coefficient, and compare the fault statistics of the meteorological three-element instruments of 3 models during the study period. The results show that:(1) The numbers of faults of the underground fluid instruments of 12models with different service times are basically positively correlated with the numbers of the corresponding instruments, with good consistency. Moreover, the automatic observation instruments(8models) with more than 30 units are significantly correlated at a 0.05 significance level(95% confidence level). Even at a 0.01 significance level(99% confidence level), there are 7 models(7/8) with significant correlation.(2) The positive and negative correlations between the monthly average number of faults and the corresponding service times of the underground fluid instruments of 12 models with different service times are random, and there are 9 models(75%) with no significant correlation at a 0.05 significance level(95% confidence level), while 12 models(100%) with no significant correlation at a 0.01significance level(99% confidence level).(3) The monthly average numbers of faults of the underground fluid instruments of 12 models are basically 0.02-0.05 times/(unit·month), and the overall fault frequency is low.(4) The fault statistics results of the meteorological three-element instruments of 3 models are consistent with the characteristics of the underground fluid instruments of 12 models. In general,there is no significant correlation between the fault frequency and the service time of underground fluid instruments.(5) The results of this paper demonstrate that the service time of underground fluid instruments cannot be taken as the main reason for whether to update the instruments. Similarly, the fault frequency of the instruments cannot be taken as the main reason for the service life of the instruments in the process of formulating the service life standards of underground fluid instruments.

Review of Research Progresses on the Science of Earthquake Underground Fluid in China During the Last 40 Years

This paper presents a review of the development of scientific research and practice of earthquake underground fluid in China during the last 40 years, summaries early constructive research and primary achievements in this field. The science of earthquake underground fluid is closely correlated with earthquake monitoring and prediction, such as innovations in observation techniques and theoretical methods, and analysis of diversified parameters and research into predictive methods. The historical evolution of observation networks for underground fluid indicates that the demand for strong earthquake monitoring and prediction has become the driving force of the construction and development of the observation network. The development of observation techniques represents the trend based on multiform measurement, syntheses, and digitization. The study results of underground fluid theory and precursory mechanisms suggest that the precursory model, numerical simuiation and in-door or field experimental research are the main technological approaches promoting innovation. Research results of earthquake forecast methods use physics based forecast techniques and the ideas of combination of usability and scientific advance. It has been proved by forecast practice that studying underground fluid is a very important subject in earthquake prediction on the Chinese mainland. Finally, the primary work and technical criterion on underground fluid are introduced, and some major scientific issues and development trends in different historical stages are summarized.

Study on Typical Characteristics of Short-Term Precursors in Underground Fluid

The underground fluid short-term anomalies of earthquake activity are studied. Two kinds of typical characteristics of precursors, the turn-around type and the single type, are summarized. Through studying regional characteristics of earthquake precursors in North China (including Northwest China) and Southwest China, we find that the two types of precursors are strongly related to geological structures in regional distribution and they show varying characteristics with earthquake magnitude in number.

The Co-seismic Response of Underground Fluid in Yunnan to the Nepal MS8.1 Earthquake

In this paper,statistics are taken on the co-seismic response of underground fluid in Yunnan to the Nepal M_S8. 1 earthquake,and the co-seismic response characteristics of the water level and water temperature are analyzed and summarized with the digital data. The results show that the Nepal M_S8. 1 earthquake had greater impact on the Yunnan region,and the macro and micro dynamics of fluids showed significant co-seismic response. The earthquake recording capacity of water level and temperature measurement is significantly higher than that of water radon and water quality to this large earthquake; the maximum amplitude and duration of co-seismic response of water level and water temperature vary greatly in different wells. The changing forms are dominated by fluctuation and step rise in water level,and a rising or falling restoration in water temperature. From the records of the main shock and the maximum strong aftershock,we can see that the greater magnitude of earthquake,the higher ratio of the occurrence of co-seismic response,and in the same well,the larger the response amplitude,as well as the longer the duration. The amplitude and duration of co-seismic response recorded by different instruments in a same well are different. Water temperature co-seismic response almost occurred in wells with water level response,indicating that the well water level and water temperature are closely related in co-seismic response,and the well water temperature seismic response was caused mainly by well water level seismic response.

A simulating experiment on the geochemical variation trend at the initial period of meteoric waters converting to underground waters and ore fluids

Experimental studies were undertaken on leaching of sedimentary rocks (dolomite and sandstone) and Hg, Sb ores by distilled water under the condition of a completely open system (room temperature and room pressure). The aim is to find whether the halogen elements or metal elements first enter the solution at the early stage of meteoric waters converting to groundwaters and ore fluids, and, at the same time, to understand how and when they enter distilled water solutions from the rocks. The experimental results have shown that F and Cl began to enter the fluids in the initial period of thirty days. With increasing leaching duration, the amounts of the elements that entered the fluids increased steadily. During the period from 120 days to 150 days the amounts increased more drastically, followed a slow increase. It is found that the capability of Cl entering the solutions is much greater than that of F. Hg and Sb were found not to have entered the solutions till 120 days later. During this period of time the pH value of the solutions began to drop. As for Hg and Sb ores, Hg and Sb began to enter the solutions on the 60th or 90th day, greatly ahead of schedule, but the two metallic elements in the rock samples began to enter the solutions 150 days later. Relatively speaking, Hg is more easily leached out than Sb from the rocks. In some rock samples, Sb could be detected in the solutions at the end of the experiment. However, Cu, Pb and Zn had not been detected in the leaching solutions from the beginning to the end of the experiment. In the whole leaching process the pH value of the solutions tend to decrease slowly from {7.1} at the beginning to {6.5} at the end. That is to say, in the interaction between pure water and rock the halogen elements in the rocks were preferentially leached out and then entered the fluids. With increasing water/rock reaction duration and amount of halogen-group elements in the solution and with decreasing pH value of the solution, some active metallic elements began to release in small amounts. This experimental result can explain the source and mechanism of volatile components and trace metals in underground waters. Meanwhile, as for those ore deposits produced by ore fluids derived from meteoric waters, the experimental result is also helpful to the understanding of the geochemical variation trend at the initial stage of conversion of meteoric waters to ore fluids.

2014年霍山M_(S)4.3地震前后重磁场变化特征及机理分析

文中利用安徽省及周边地区2010—2015年流动重力和2013—2014年流动地磁资料,系统分析了霍山地震前后重力和岩石圈磁场三分量随时间的变化特征,利用小波分析法提取震前重磁场变化不同分解尺度的小波细节,结合地下流体资料探讨了霍山地震的发震背景和震前地球物理场前兆异常明显的原因。霍山地震前,重力场与岩石圈磁场总强都形成了异常变化的高梯度带,异常范围约为100km,梯度带的走向与发震断裂一致,地壳形变与地下流体运移明显受到构造断裂的控制。岩石圈磁场总强在霍山地区出现了较大幅度下降,重力场经历了“区域整体微小负值变化—形成重力异常高梯度带—在重力变化零等值线附近发震”的演化过程。震前半年“霍山窗”开窗,小地震活动显著增强,区域地壳运动水平显著上升,加速了区域应力状态的调整与地下流体的运移,导致了重磁场震前的显著变化;小波分析结果显示,磁场变化的极值点靠近重力场变化的零值线及断裂发育区域,表明重力场与岩石圈磁场的变化具有一定的相关性,进一步揭示了基于重力与岩石圈磁场变化等地球物理前兆信息预报地震的可能,结合区域应力场、地下流体、重力场与岩石圈磁场变化的综合分析,更有利于震前地震危险区的划定及危险性研判。

辽宁盘一井地下流体异常特征、预测方法及异常成因研究

辽宁盘一井地下流体自1973年开始观测以来,发展至今不仅流体观测手段逐渐丰富,积累了大量观测资料,并在多次地震前出现明显异常,为地震监测预报提供了重要借鉴,本文对辽宁盘一井地下流体异常特征、预测方法及异常成因进行了研究。对盘一井不同测项的震前异常特征及预测方法分析结果表明,水氡以趋势性和临震异常为主,氢气以短临异常为主,使用阈值法、差分分析法及临界慢化法识别异常效果较好;氯离子以短临异常为主,使用原始曲线分析方法提取异常效果较好。盘一井水氡异常成因分析表明,盘一井各测项浓度异常与测点周边地震活动强弱、区域应力场变化等存在紧密关系。在压应力状态下,该井氡浓度异常往往表现为高值异常;在张性应力状态下,该井氡浓度异常往往呈“V”字形态变化。

广东地震地下流体监测网质量与效能分析

依据流体学科相关评价标准,从广东地下流体观测网观测环境、观测仪器、观测质量和预测应用方面着手,结合地下流体学科台网中心提供的台站网运行监控和质量监控情况,对地下流体观测网每个观测站的观测环境、仪器的运行情况、观测仪器产出的数据的质量及其预测应用情况进行了评估。结果显示,观测站观测环境满足二类台站居多;观测数据运行率为优秀者占比:水位、水温和氡各为77.8%、63.6%和100.0%;流体仪器数据完整率全部为优秀;预测应用效能井水位和氡均为良好,水温有88.9%为良好。通过评估,较全面地分析了广东地下流体观测网存在的问题,并针对存在的不足提出改进措施及建议。

2021年玛多7.4级地震聊古1井同震响应特征分析

整理了聊古1井流量、水位、水温和水化学离子含量等流体测项在2021年青海玛多7.4级地震中的同震响应变化特征。结合聊古1井的构造背景,分析了同震变化的影响因素,初步探讨了同震变化机理。结果表明:聊古1井流量、水位及水温等流体测项在青海玛多7.4级地震发生后呈阶升型同震变化,井水离子含量也出现较大波动,明显高于背景值。本次青海玛多7.4级地震的流体同震响应特征表明聊古1井对远场地震反映灵敏,具有良好的映震效能。

鲁南地区流体监测台网优化与监测效能评估

结合鲁南地区地质构造背景,通过自主研发的高精度水位水温实时监测仪器,对地下流体监测站点软硬件设施进行升级改造,建设鲁南地区地下流体数字化监测台网。同时,构建基于层次分析法的鲁南地区地下流体监测效能评价体系,利用模糊综合评价法对各观测站点进行量化的效能评估,为进一步提升该地区地下流体监测台网监测能力提供参考意见。

高富水复合砂层盾构隧道渗透破坏原因分析

特殊的地层条件及水力条件是事故发生的关键因素。本文通过砂土流失模型试验,发现单一砂层、复合砂层的渗流破坏特征存在显著不同。单一砂层和“上粗下细”复合砂层的侵蚀空洞呈漏斗形,而“上细下粗”复合砂层的侵蚀空洞呈碗形。当渗流出口处于粗细交界面时,上细下粗的复合砂层,使大部分的水头损失消耗在上部的细砂层中。相同条件下,“上细下粗”复合砂层中的渗流破坏最为强烈。广东某地铁区间突发涌水涌砂导致地面坍塌。事发地为珠三角河网地带,盾构机处于由下层中粗砂和上粉细砂组合而成的复合砂层中,同时邻近河涌强供水,两种结合极易发生涌水涌砂,引发周围地层砂水快速流失,造成上覆土层的大面积塌陷。试验结果与现场现象相吻合,揭示了高富水复合砂层中容易导致事故的地层和水力方面原因及上述多种因素组合致灾的机理。在类似工程勘察设计阶段,需重视复合砂层的识别,并做好盾构的“密封”措施,防止渗流出口的出现。

富水区地下泵房渗流场及其对衬砌结构影响的数值分析

地下水在地层中运动会影响地下泵房结构的安全,在渗透水压力作用下洞室围岩易引发渗透问题致使洞室及厂房内部渗水,高地下水位产生的外水压力会影响地下洞室厂房衬砌结构安全。结合某富水区泵站工程,采用数值分析方法,构建了三维有限元模型,基于流固耦合理论,对工程区的渗流场进行分析,并研究了不同灌浆圈厚度、不同衬砌透水性下工程区外水压力变化规律。结果表明,增加灌浆圈厚度或增强衬砌的透水性均可降低衬砌外缘上的外水压力,研究成果可以为类似工程提供参考。

煤炭地下气化通道传热下顶板岩温度和应力研究

针对煤炭地下气化中的顶板岩稳定和气化热利用问题,建立了热—流—固耦合的流场和应力场计算模型,模拟研究了气化通道传热下顶板岩的温度、应力变化。结果表明,燃烧面前的顶板岩升温幅度低于燃烧面后的;随着燃烧面的推进,气化通道周围顶板岩的升温幅度和升温区域增大;高温可大幅增加顶板岩底部的拉应力和剪应力,最大可增加10倍以上;最大拉应力和最大剪应力发生在燃烧面所在的顶板岩底部位置,顶板岩主要发生拉伸破坏。

缝洞型碳酸盐岩储气库地应力变化特征及力学完整性研究

缝洞型碳酸盐岩储层非均质性极强,储集空间结构和渗流关系复杂,为地应力分析、注采参数选择、力学完整性评价带来了诸多挑战。因此,为进一步明确缝洞型碳酸盐岩储气库运行过程中的地应力变化、保证储气库运行过程中的力学完整性、提高上限压力,建立机理模型,分析缝洞型碳酸盐岩储气库应力分布特征及四维地应力变化规律,同时评价不同介质力学完整性。结果表明:①缝洞型碳酸盐岩储层相较于均质储层在缝洞处应力集中较为明显,尤其溶洞边界易出现应力的极小值;②缝洞处孔隙压力及应力变化更为剧烈,储气库运行过程中溶洞边界更易发生剪切或张拉破坏;③在采气过程中,溶洞边界沿最小主应力方向更易发生剪切破坏,注气过程中,溶洞边界沿最大主应力方向更易发生张拉破坏;④缝洞型储层整体相较于均质储层更易在注气过程发生张拉或剪切破坏,采气过程缝洞型储层整体较为安全,但洞周围更易发生剪切破坏。研究成果可为缝洞型碳酸盐岩储气库地应力分析和力学完整性评价工作提供理论及方法支撑。

考虑流固耦合的露天坑积水下边坡与巷道协同稳定性研究

露天矿边坡与巷道协同稳定性是影响矿山安全开采的关键因素。开展矿区边坡与巷道协同稳定性研究是保证矿山能进行安全施工的重要工作之一。针对矿区Ⅵ号矿组露天坑目前存汇水问题,分析论证后续井巷开采、工程力学、汇水等因素对Ⅳ号矿组、Ⅶ号矿组深部井巷工程是否有影响;采用3Dmine建立了露天矿三维地质模型,截取风险边坡剖面并建立数值模型,结合COMSOL Multiphysics多场耦合分析软件,对建立的剖面模型的渗流场与应力场进行耦合,通过精细化划分网格对其进行稳态求解,得到剖面模型的损伤区、应力场及位移变化云图,其中,边坡5号剖面区域基坑存在积水问题,在求解过程中考虑渗水条件。分析结果表明:Ⅵ号露天边坡、Ⅶ号露天边坡岩体损伤对地下工程均未造成影响,Ⅵ号矿坑积水的渗透速度分布在10^(-7)~10^(-6)m/s,由于渗透速度较低,Ⅵ号矿坑汇水并未对附近地采工程稳定性造成显著影响;建议对Ⅵ号矿坑汇水进行及时抽排,并加强Ⅶ号露天边坡位移监测。该研究结果为论证边坡与巷道协同稳定提供了新思路和参考。

我国钻井液技术难题、新进展及发展建议

系统地梳理了超深/特深层、非常规、深水、干热岩、极地、天然气水合物等复杂地层钻探过程中面临的钻井液技术难题,探讨了关键科学问题与核心工程难题,结合近年来的钻井液技术进展,介绍了钻井液技术最新进展。针对复杂地层钻井过程中遇到的高温高压高盐、泥页岩水化严重、井壁失稳、大温差、井漏、储层损害,以及钻井液维护自动化程度低等问题,国内外学者研发了抗高温高盐水基/油基钻井液、恒流变钻井液、抗超高温泡沫钻井液、环境友好型超低温钻井液、智能温压响应承压堵漏材料、可降解储层保护材料、钻井液在线监测与自动加料系统等关键材料、体系与装备。但随着地质、工程环境愈加复杂,钻井液材料仍面临抗超高温高盐、超长时间稳定、防塌固壁、恶性漏失以及钻井液性能自动化调控等重大技术瓶颈。为满足复杂地层钻探过程中钻井液性能需求,未来还需深入研究钻井液处理剂在极端条件下的起效/失效机理,钻井液处理剂在微观-介观-宏观等不同尺度下的构效关系变化及作用机制,建立安全高效的钻井液多功能一体化调控方法,构建智能钻井液理论与技术,为实现复杂地层安全高效经济环保钻井提供关键技术支撑。

超大型地下结构系统地震响应高性能弹塑性流固耦合分析

随着城市地下空间开发进行加快,地下结构的抗震安全问题日益受到重视。为了研究饱和土层,尤其是可液化场地中超大型地下结构的地震响应,必须解决高性能计算、弹塑性本构模型、流固耦合等关键问题。该文基于高性能数值仿真平台GEOSX,开发一套高性能弹塑性流固耦合分析方法。以北京城市副中心站综合交通枢纽为例,采用砂土液化大变形模型进行动力弹塑性流固耦合分析,计算规模超千万自由度。计算结果表明,所开发的分析方法具有较高的并行计算效率,可以实现可液化场地地下结构系统的大规模高效弹塑性流固耦合模拟。对于这一主要处于饱和砂土地层中的超大型地下结构系统,在基本地震作用下,饱和砂土层的最大超静孔压比达到约0.5,产生较为明显的弱化;结构地震层间位移角和内力均满足规范要求,由于存在开洞等断面变化,结构响应三维效应明显;由于与地下结构相连的地上结构相对较小,地上结构对地下结构地震响应影响有限。

Response Difference and Related Discussion of Digital Fluid Records of the Beijing Wuliying Well before Strong Earthquakes

In this paper, the precursor response characteristics of digital fluid caused by the Wenchuan M8.0 and Yushu M7.1 earthquakes are studied, and the response difference of the observations of Wuliying well to the two strong earthquakes is compared. The result shows that the abnormal fluid response has a certain relationship with earthquake size and epicenter distance. The greater the earthquake, and the closer it is to the epicenter from the observatory, the more sensitive the response will be to fluid anomalies. Abnormal Helium release was first observed before both strong earthquakes in the fluid precursor observation. The release intensity is related to earthquake magnitude; the larger the magnitude, the stronger the abnormal changes. The large change in He release in a short period after the Wenchuan earthquake may be related to the continuous activity of strong aftershocks and the structural adjustment after the earthquake. Helium release increased significantly after both earthquakes, as contributed by the abnormal deep-sited Helium release. However, this process may be connected to the annual change from July to September or the hot-reservoir type gas release in the Wuliying well. In the earthquake preparation process, a large number of deep-derived Helium is released into the geothermal system and the entire composition is changed. Temporally, this gas release appears later than fault-type gas release, and the disappearance time of this anomaly is also much later. The response difference of the fluid precursor to the two strong earthquakes may be related to differences of deep structural setting and dynamic mechanism. It also shows there is a stronger correlation between Wenchuan M8.0 earthquake in the North-South Seismic Belt and North China region than the Yushu M7.1 earthquake in the internal Qinghai-Tibetan plateau. Helium gas can be a sensitive indicator for monitoring abnormal deep-gas activity of the region where the observation station is located. Hence, observation and research should be strengthened in the future.

采动水浸作用下煤柱坝体承载特征与失稳规律研究

煤矿地下水库的储水技术已成为我国西部矿区煤炭资源开采与水资源保护协调发展的重要途径之一,而煤柱坝体的稳定性是煤矿地下水库能够安全并长期使用的关键因素。为了探究煤矿地下水库煤柱坝体在复杂条件下失稳特征,基于FLAC3D数值模拟及二次开发,以陕西北部某矿相邻工作面开采及采空区蓄水的水浸作用对煤柱坝体应力演化特征及稳定性的影响展开研究。结果表明:工作面开采完毕后,煤柱坝体应力分布均呈现双峰形,并随煤柱宽度的增加峰值逐渐下降,同时煤柱宽度为20 m时其弹性核区占比小于40%的临界失稳指标,将发生失稳;在采空区蓄水后,水浸作用下煤柱坝体塑性区占比增量呈现“稳定-增大-减小-稳定”的变化规律,能够很好地模拟水浸作用下煤柱坝体的“渗流-弱化-损伤-渗流”的渐进破坏特征;煤柱坝体的应力分布逐渐演化为拱形分布并趋于平均化,应力峰值大幅降低,同时,内部塑性区进一步扩展,弹性核区占比降低,且煤柱宽度的越小降低幅度越大;当煤柱宽度为30 m时,弹性核区占比降低为38.33%,将发生失稳;当煤柱留设宽度为40 m时,煤柱能够保持稳定。

吐哈油田超低压储气库钻井工程方案优化设计与应用

温西一储气库是吐哈油田首座超低压气藏型储气库,目的层是侏罗系西山窑组,气藏压力系数仅为0.20~0.22,垂直裂缝发育,盖层及以上发育大段泥页岩,极易水化剥落,井漏与井塌并存对优快完钻带来了极大挑战。通过综合评估温西一库超低压气藏地质及钻完井条件并深度吃透储气库设计要求,对储气库注采井钻井工程方案进行了优化设计:①采用三开结构,技术套管下至储层顶1~2 m;②生产套管采用韧性微膨胀水泥浆体系,固井工艺采用尾管悬挂+套管回接;③三开钻井应用聚胺钻井液体系配合凝胶复合承压堵漏技术。形成的温西一库钻井工程方案经现场实践证明,完钻井漏失量较前期降低50%以上,固井合格率均大于70%,盖层段连续优质超40m,满足储气库全生命周期井筒完整性要求,为国内同类型储气库建设提供了技术借鉴。