力学温度和化学耦合作用下泥页岩地层井壁失稳研究

为减少泥页岩地层,特别是高温-高压泥页岩地层的井眼失稳问题,将泥页岩地层视为孔隙介质,在综合考虑岩石特性、井眼周围三维地应力、化学及热效应等因素对泥页岩地层井眼稳定的影响的情况下建立了井眼周围有效应力计算模式,通过有限差分法进行求解。结合地层失效准则,得到了温度、渗流以及岩石特性对坍塌压力和破裂压力的影响规律。研究的结果表明对低渗透率的泥页岩来说,热效应以及化学反应在确定钻井液密度窗口时起到重要作用。计算结果对实际钻井有理论上的指导意义。

矿区地层结构弱化与矿区地震灾害

我国为地震多发国家,许多矿区都位于高烈度地震设防区。煤炭开采使得矿区地层结构严重弱化,由于采掘作用而诱发的矿区地震发生频繁。文中分析了导致矿区地层结构弱化的主要因素和矿区主要地震灾害的类型,并对矿区地层结构弱化对矿区地震灾害的关系进行了探讨。指出矿区地层结构的弱化不仅降低了系统自身稳定性的调节能力,而且起到了系统内部加载的作用,是发生矿区诱发地震的前提;另一方面,弱化的地层结构其抗震能力大大降低,其地面和地下构筑物在地震力的作用破坏将更严重。

利用测井资料合成井壁破坏图像分析地应力新方法

利用测井资料进行地应力分析关键在于确定水平方向构造应力系数。提出一种确定水平方向构造应力系数的新方法,通过调整水平构造应力系数计算地应力,利用地应力计算结果结合井壁破坏模式合成井壁破坏图像,将该图像与电成像测井资料进行对比,当二者反映井壁破坏情况相符时,此时的水平构造应力系数可作为该区的水平构造应力系数,由该水平构造应力系数即可得到地应力沿深度变化的剖面,为地应力分析提供了一种新的思路。

控压钻井过程中泥页岩井壁破坏分析

控压钻井过程中,控制井底压力与地层压力相当,可以减少井壁由于井底压力过小或过大引起的井壁坍塌或破裂问题。对于水敏性泥页岩地层,即使在压力平衡的情况下,由于水基钻井液和泥页岩之间的水化渗透作用,泥页岩井壁也有可能不稳定。为此,建立了控压钻井条件下泥页岩井壁稳定非线性流—固—化耦合新模型,考虑了离子扩散与岩石变形的全耦合以及流体流动和离子扩散过程的非线性;通过有限元分析泥页岩井壁周围孔隙压力场和应力场的变化,计算井壁周围地层破坏系数,检查井壁是否破坏。研究结果表明:①控制压力钻井与常规钻井相比,水化渗透引起的孔隙压力剖面变化较小,有利于泥页岩井壁稳定;②泥页岩井壁失稳主要有井壁破坏、井壁附近地层破坏两种方式且后者是有时间效应的;③现有模型与非线性全耦合模型相比,过大地预计了井周孔隙压力和总应力且其压力峰值传播较慢;④泥页岩井壁失稳后,新的泥页岩表面暴露在钻井液中继续进行水和溶质交换,井眼扩大到一定值后,发生进一步失稳的可能性较小。

上行开采条件下巷道修复时机和开切眼位置研究

为避免煤矿开采过程中上部采区巷道的重复返修问题,采用理论分析、数值模拟和工程测量相结合的方法,对下伏煤层开采过程中覆岩破坏特征和巷道塑性区演化特征进行了研究,揭示了下伏煤层开采对煤层完整性和巷道稳定性的影响规律,确定了上煤层巷道的修复时机和下煤层工作面开切眼的合理位置。煤矿开采期间,由于受下伏煤层工作面开采的影响,上采岩层塑性破坏严重,虽未出现阶错,但出现整体沉陷,上煤层巷道的修复时机应在塑性区范围趋于稳定后;开切眼位置应综合考虑围岩变形幅度最小及煤炭资源充分利用等情况。现场工程应用表明,采取上述措施后,巷道围岩变形满足煤矿生产要求,避免了巷道围岩变形的多次修复。

浅覆盾构隧道环向挤出破坏上限有限元分析

针对软弱地层浅覆盾构隧道未支护段地层挤出破坏问题,基于极限分析上限有限元法,结合节点可动的刚体平动运动单元,建立了隧道环向开挖面挤出破坏的非线性规划模型并编程求解。通过参数敏感性分析,研究了地层参数、隧道埋深等因素与临界加载系数间的曲线关系,并探讨了刚性块体体系破坏模式的演化特征。结果表明,临界加载系数σT/c随φ、γD/c和C/D的增加而增加;φ对地层破坏模式影响显著,φ值越大,滑动面与竖向夹角越大;刚体平动运动单元法能使单元间的速度间断线自动调整至最佳方位,利用较少的单元可获得较好的上限解,并清晰的反映出土层破坏形态。

CO_2地质埋存后的逃逸问题研究进展

中国的温室气体排放目前已排世界第一,对环境是严重的威胁.CO2地质埋存是温室气体资源化利用及减少大气温室气体排放量的有效途径之一,但是在地质埋存后,CO2一旦逃逸会引起地表的隆起或凹陷、污染水源、破坏海洋生态系统等系列灾害,并使温室气体埋存效果毁于一旦.本文在对CO2埋存问题简要介绍的基础上,重点对埋存后CO2逃逸问题的研究现状作综述.阐述了CO2埋存后通过盖层渗流和扩散、废弃井的渗透等逃逸方式,以及主要的控制参数,包括盖层渗透逃逸、扩散逃逸、油井及裂隙逃逸等方面的参数.通过分析,提出了需要进一步研究的问题,主要有:(1)控制CO2逃逸的主要参数需要通过模型实验确定;(2)需要建立考虑化学反应、地层特征和井口分布特征的多相渗流模型;(3)在CO2逃逸方面除要考虑扩散、渗流效应外,还要考虑井口分布、高气压引起的劈裂导致的渗透性急剧增加的效应等因素的影响.

基于ICP技术的天然气水合物开采方案

天然气水合物(NGH)矿产储量巨大,燃烧后几乎不产生任何残渣,是一种高效利用的清洁能源。为了提出天然气水合物切实可行的开采方案,对天然气水合物成藏特点进行分析,通过当前室内研究的天然气水合物开采方法比较,并考虑到真实开采过程中可能出现的地层破坏问题,在CO_2乳状液置换天然气水合物中CH_4实验和页岩油ICP开采技术的启发下,最终制订出一套具有井工厂特点的天然气水合物开采方案。研究得出:ICP技术核心工艺冷冻墙、加热井井网布置能有效克服热散失,并持续提供热量促进天然气水合物分解。CO_2乳状液置换技术能在高效产出CH_4情况下形成CO_2水合物,防止地层因为天然气水合物分解而产生的地层破坏。注采监测系统的部署能实时监控生产反应过程,可操作性强,控制精度高。

天然气水合物热分解引起多场响应的特征时间分析

天然气水合物是我国的战略能源,而要实现商业化开采,必须首先回答如何避免引发地质灾害与环境问题。开采过程涉及传热、水合物相变、渗流、地层软化与应力重分布的多场响应,进而可能引起地层破坏,甚至大尺度塌陷、滑坡、甲烷喷发泄漏等灾害。本文针对天然气水合物热分解引起多场响应的问题,通过量纲分析得到传热、水合物相变、渗流、地层应力重分布的特征时间,进一步比较分析发现,它们的时间尺度之间相差2个数量级以上,从而提出解耦分析方法,该方法已在系列模型实验设计与理论分析中得到应用。

Experimental investigation into stress-relief characteristics with upward large height and upward mining under hard thick roof

According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.

Treatment effect investigation of underground continuous impervious curtain application in water-rich strata

Serious shaft lining failures often occur when shaft linings are constructed by passing them through the deep topsoil of Quaternary strata. This approach also leads to the formation of an aquifer at the bottom.Based on the theory of the additional stress which is the main reason for these failures, this study focuses on the treatment effect of underground continuous impervious curtain(UCIC) in terms of different factors, namely, the location, shape, range, and width, by using numerical simulation. Results show that the UCIC can reduce the stress concentration in the shaft lining formed in the bottom aquifer. The UCIC can also reinforce the shaft lining at different angles and can be applied in actual situations. The strength factors of the inner surface of the shaft lining increase after the UCIC are used. The material strength and width of the UCIC show an obvious effect on the stability of the shaft lining. Results proved that the UCIC could effectively strengthen the stability of the shaft lining when it was built in the aquifer or built in the aquifer and above and below the layer.

Dynamic failure mode and energy-based identification method for a counter-bedding rock slope with weak intercalated layers

The dynamic failure mode and energybased identification method for a counter-bedding rock slope with weak intercalated layers are discussed in this paper using large scale shaking table test and the Hilbert-Huang Transform(HHT) marginal spectrum.The results show that variations in the peak values of marginal spectra can clearly indicate the process of dynamic damage development inside the model slope.The identification results of marginal spectra closely coincide with the monitoring results of slope face displacement in the test.When subjected to the earthquake excitation with 0.1 g and 0.2 g amplitudes,no seismic damage is observed in the model slope,while the peak values of marginal spectra increase linearly with increasing slope height.In the case of 0.3 g seismic excitation,dynamic damage occurs near the slope crest and some rock blocks fall off the slope crest.When the seismic excitation reaches 0.4 g,the dynamic damage inside the model slope extends to the part with relative height of 0.295-0.6,and minor horizontal cracks occur in the middle part of the model slope.When the seismic excitation reaches 0.6 g,the damage further extends to the slope toe,and the damage inside the model slope extends to the part with relative height below 0.295,and the upper part(near the relative height of 0.8) slides outwards.Longitudinal fissures appear in the slope face,which connect with horizontal cracks,the weak intercalated layers at middle slope height are extruded out and the slope crest breaks up.The marginal spectrum identification results demonstrate that the dynamic damage near the slope face is minor as compared with that inside the model slope.The dynamic failure mode of counter-bedding rock slope with weak intercalated layers is extrusion and sliding at the middle rock strata.The research results of this paper are meaningful for the further understanding of the dynamic failure mode of counter-bedding rock slope with weak intercalated layers.

Application of Dangerous Probability Function in Risk Estimation of Surface Rupture Earthquake: Taking the Lingwu Fault in Ningxia Region as an Example

Based on the fitting on paleoearthquake data of intra-plate regions in the northern part of China and giving a statistical model of time interdependence, the potential damage earthquakes in a definite future period and characteristics of present shocks along the Lingwu fault have been analyzed by using dangerous probability function and some new data concerned. We have inferred that the fault has entered a period that earthquakes will probably occur. There exists a potential danger that a strong earthquake with M\-S7.0～7.5 will occur in 10～100a.

Seismic Risk Assessment and Maximum Magnitudes of Potential Earthquakes on Active Faults near Lanzhou City

The Zhuanglang river and Baiyin Baiyangshu river faults are late Quaternary faults near Lanzhou city, which pose a threat to the safety of the city. However, the cause of medium- strong earthquakes along the fault is rather complicated and even uncertain. It is important for us how to assess the magnitudes of maximum potential earthquakes and the seismic risk of the faults. The authors make reference to the method that Wen Xueze, et ai. （2007） developed to assess the magnitudes of maximum potential earthquakes in sub-areas of moderately and weakly active faults in the eastern Chinese Mainland, and brought forward an empirical relationship between the maximum magnitudes Mmax and the at/b values of the sub-areas＇ frequency- magnitude relationships in the Lanzhou area. By using this empirical relationship, the authors have estimated the upper-limits Mu of the Zhuanglang river and Baiyin Baiyangshu river active faults near Lanzhou city as Ms6.9 and 6.3, respectively. In addition, they have assessed the average interval recurrence time and the probabilities of destructive earthquakes on the faults.

Research on ETABS Steel Tower atop Building Structural System

Equipping steel tower atop building structural system at the top of high-rise buildings is applied increasingly. However, the earthquake disasters indicate that under seismic effect, the tower on the roof reacts strongly to the earthquake, and the gazebo is damaged greatly under the condition that major structure has no earthquake damage. Based on analyzing the characteristics and application methods of ETABS software, for engineering projects, the paper uses ETABS software and simplified calculation method to calculate and make comparison analysis on steel tower atop building structure. The analysis results indicate that the method established in the paper has higher accuracy, which can meet the engineering requirements.

Paleo and New Earthquakes and Evaluation of North Tabriz Fault Displacement in Relation to Recurrence Interval of Destructive Earthquakes

Azerbaijan is one of the most active segments of the Alpine-Himalayan seismic belt and marks the junction between the African-Arabian and Indian plate to the south and Eurasian plate to the north. Several regional earthquakes have been strongly felt and caused damages in and around Tabriz during history. For example, the magnitude 7 to 7.7 Tabriz earthquake in 1780, which is the most strongest experienced one in Lesser Caucasus and east of Turkey and caused severe damage in Azerbaijan territory including Tabriz City. The urban area of Tabriz City lies on Miocene to Quaternary soft sediments （clays, sands, silts, and gravels.） resting on an old Tertiary basement. Previous studies have shown that the thickness of such soft sediments could largely influence the site response in case of an important regional earthquake. The accurate information about historical earthquakes and new faulting is an important tool for viewing the active tectonic and analyzing the earthquake risk and seismic migration. Historical records of earthquakes in Tabriz based on macro and micro seismic observations cover period of 1,000 to 1,400 years. Our study aims at mapping the seismic response of a pilot zone of Tabriz for different earthquake scenarios, a simple but robust.

循环荷载作用下高炉基础沉降规律研究

高炉基础作为大体积混凝土设备基础之一,受力较为复杂,基础沉降要求严格。铁水的反复增减装卸,导致基础不断承受循环荷载,增加了基础沉降风险。对此研究以福建龙钢炼钢炉基础为依托,通过数值模拟分析了不同铁水荷载下基础的变形特征,研究得出以下结论:循环荷载作用下高炉基础处于不断加载卸载过程,满载时结构最大沉降为11.983mm。循环加载易导致基础下部中风化岩石发生剪切破坏,中风化与强风化岩层分界点已发生离层。采用注浆加固后,基础满载时沉降降低了64.23%,土体稳定性增强。研究可为炼钢高炉基础设计及处治提供借鉴。

关于油田防砂方法浅析

原油在地层压力驱动下流入井筒的过程中,会携带一些砂粒进入井筒内,特别对疏松砂岩稠油油藏地质,产生极大的危害。主要危害表现:井壁失稳、套管损坏、地层破坏、井下及地面设备的损害、管线的磨蚀及堵塞、油层被砂埋等等。这些危害既提高了原油的生产成本,又增加了油田的开采难度。因此,积极的防砂措施是应对出砂的途径。

Effect of tidal stress on fault nucleation and failure of the 2007 Ms6.4 Ning＇er earthquake

Based on calculations of the tidal Coulomb failure stress and investigations of the correlation between the Earth tide and the Ning＇er earthquake sequence, the processes of fault nucleation and failure were simulated. In these simulations we consider the influence of tidal stresses using the rate- and state-dependent friction laws. Furthermore, the effects on tidal trig- gering due to the stress amplitude and periodic oscillation properties were investigated, and the triggering effects between the tidal normal and tidal shear stresses were compared. The results showed that the Ning＇er earthquake sequence was a physical consequence of tidal effects. A transition period To exists between the nucleation and failure processes of a seismic fault. When the period T of stress is equal to or becomes larger than To, the fault response becomes dependent on the periodic features of the loading stress; however, for T 〈 To, the response of the fault is nearly independent of the period. Both the tidal normal and tidal shear stresses have similar effect in the nucleation and failure processes; the clock changes generally increase with the maximum amplitudes of the tidal stresses. Tidal normal and tidal shear stresses with positive amplitudes mainly induce earth- quake triggering; however, the triggering effects induced by negative tidal stresses are smaller and faults are not sensitive to negative tidal stresses. Our results primarily reveal the physical mechanisms of tidal stress triggering.