Electromagnetic emissions during dilating fracture of a rock

A lot of experiments on electromagnetic emissions (EMEs) have been reported under axial compressive fracture, shear fracture, indentation fracture and stick–slip (friction) in lab and blasting in situ, but there are rare reports on the in-lab experimental work on EMEs during dilating fracture of a rock which is helpful in studying and understanding EMEs related to slow earthquakes and the earthquakes due to volcanic activities and water level changes of reservoirs. Therefore, in the present paper in order to check whether there are detectable EMEs during dilating fracture of a rock in lab, dilating fracture experiments were conducted. The dry cuboid specimens of initially intact granodiorite and limestone were tested inside magnetic field free space (MFFS) at room temperature. We arranged evenly 20 EME antennas whose resonance frequencies range from 2.5 kHz to 540 kHz close to rock specimens. Our experimental results strongly indicate that detectable EMEs could generate during dilating fracture of a rock. They were recorded only associated with some but not all phases of fracture. Their waveforms often took on the trend that a peak arrived at first and then attenuated sharply and followed by a series of low-amplitude oscillations. The electromagnetic (EM) signals after eliminating the effects of EME antennae via deconvolution had the maximum peak-to-peak amplitudes of about 80.0 mV and 40.5 mV for granodiorite and limestone, respectively. Their main spectral components often concentrated in the band of several kHz to ∼60 kHz and of several kHz to ∼280 kHz. The emission of electrons and charged particles from fracture surfaces and/or micro-fracture electrification could be possible mechanisms for our experimental results.     

气井水力压裂有效缝长评估及影响因素研究

为了准确确定气井压后有效缝长及其影响因素,提高川西须家河气藏水力压裂针对性,对于具备生产历史拟合条件的气井,利用数值模拟软件进行了生产历史拟合获得有效水力裂缝缝长,与采用净压力拟合方法获得的水力裂缝支撑缝长进行对比和拟合,获得了有效缝长和支撑缝长的关系式,计算了川西须家河储层单井压后有效缝长;采用灰色关联分析理论分析了各个参数对有效缝长的影响程度和对压裂设计的启示。结果表明：压后有效缝长与支撑缝长具有较强相关性(Le=00584 Lp1359 3),有效缝长明显比支撑缝长短;施工参数(特别是用液量)是影响须家河储层有效缝长的关键,而储层和隔层间应力差则是影响有效缝长的重要客观因素。该研究方法为水力压裂压后评估和提高压裂设计水平提供了较好的借鉴。     

小尖山金矿床赋矿层位及容矿裂隙特征

文章从赋矿层位、构造入手,研究了金矿形成的特殊矿源层及构造作用下的成矿裂隙特征,认为小尖山金矿位于全区含金丰度最高的石炭系下统雅满苏组地层内,差异的矿化特征主要由不同的裂隙导致形成.     

基于水平集法的非均质岩石建模及水力压裂传播特性研究

基于水平集法的基本思想,讨论了含有不同类型包裹体分布的岩石的二维和三维有限元建模方法。对于二维有限元模型的建立,考虑了以椭圆形为例的规则包裹体的周期分布、位置及包裹体大小均随机变化的多种情况。建议了包裹体和基岩之间界面的材料特性过渡处理方法。同时给出了含有非规则形状包裹体的建模方法。对于三维有限元模型的建立,则考虑了以任意大小椭球体为例的包裹体分布情况。该种建模方法的优点是对于不同的含有任意分布的包裹体的岩石试件,均可以采用相同的有限元网格,即,材料特性的变化不受有限元网格的制约。该法缺点是增加了计算资源。最后结合基于弥散裂缝模型的水力压裂数值计算方法,模拟了含有不同包裹体分布的岩石试件的水力压裂传播特点。     

阿曼Daleel油田下白垩统Shuaiba组上段走滑正断裂带裂缝分布定量评价

在对阿曼Daleel油田下白垩统Shuaiba组上段的岩芯及成像测井裂缝特征进行分析的基础上,利用过断层的水平井成像测井资料,开展对断层两侧的裂缝发育情况研究,分析认为裂缝发育密度与离断层的距离相关,提出裂缝成因主要受区内走滑正断层所控制.研究建立的3类不同规模的走滑正断层带裂缝密度分布函数,实现了对阿曼Daleel油田下白垩统Shuaiba组上段断裂带裂缝分布的定量评价.     

氡气测量在佳木斯城市地下热水普查的应用

在佳木斯城区地下热水调查中,运用了水中氡活度浓度测量和土壤氡活度浓度测量综合方法,有效地克服了城市地热地质调查中的不利因素。通过对水中氡活度浓度及土壤氡活度浓度测量值的正态化变换以及原始氡活度浓度异常分析,明确了氡活度浓度异常对地下热水控制构造的指示作用。通过对氡活度浓度测量值的趋势分析,提取局部异常,综合各种异常信息,确定了城区地下热水的有利远景区。     

Horizontal rough fracture type curves for groundwater movement

Abstract

Type curves are derived analytically for radial flow in rough horizontal fractures toward a well. The basic assumptions are that there is no turbulent flow near the borehole and the well storage is ignored. The basis of the methodology is to write explicit expressions for the continuity and cubic law flow equations, which are combined using a Boltzmann transformation leading to a simple ordinary differential equation for groundwater movement. Solutions are presented as a set of type curves for different fracture apertures. It is observed that the solutions provide a method of uniquely identifying fracture hydraulic parameters when the fracture is smooth, but pose ambiguity for rough fracture parameter estimations. However, large time portions of these type curves appear as straight lines on semi-logarithmic paper, which provides a unique way for rough fracture parameter determination. Identification of the fracture parameters, namely, the aperture and relative roughness, is possible in a unique manner with the use of these lines and the dimensionless time drawdown concept. The cubic law is the asymptotic behaviour, either for large times or large fracture apertures. Prior to this asymptotic part, there is a non-cubic portion which gives rise to systematic deviations from the cubic law. The technique presented is useful, especially for evaluating pumping tests from a single major fracture isolated by packers.     

横波各向异性在裂缝和应力分析中的应用

针对裂缝性和低孔低渗地层的横波各向异性特征,反演得到横波各向异性参数,研究了裂缝的发育程度、方位和有效性,并对低孔低渗地层的应力场分布状态和方位进行了综合评价;通过对反演得到的快、慢弯曲波形进行频散分析以及计算单极横波各向异性大小,确定了引起横波各向异性的原因,并结合常规测井资料、岩心及FMI成像资料对分析结果进行了验证和对比,最后对研究区8口典型井的横波各向异性进行了综合处理和评价,得到了该区的横波各向异性特征以及和总的应力场走向.结果表明,利用横波的各向异性参数可以有效的评价裂缝的发育程度、走向及有效性,并能准确的确定地应力分布状态和最大水平应力方位.     

单裂缝不同传播方向Krauklis波振幅变化的实验研究

裂缝广泛分布于地壳岩石中并具有多尺度的特点,研究地震波在裂缝介质中的传播规律具有重要的科学意义和应用价值.含流体的裂缝中传播的Krauklis波（也曾被称为慢流体波、裂缝波、斯通利导波等）近年来逐渐成为地球物理学界的研究热点之一.本研究利用地震物理模型技术研究横波在单裂缝样品中传播时随传播方向变化的响应特征,在实验室用环氧树脂为基质构建模型样品,一个为不含裂缝的参考样品,一个为含直径30 mm、厚度0.2 mm的薄币状单裂缝的模型,利用0.5 MHz换能器测试了横波在模型中传播时透射信号的特征.实验结果显示在单裂缝样品中透射横波发生了波形的畸变和振幅降低,振幅谱显示透射信号的主频明显降低,在初至横波之后为具有一定能量的尾波.对尾波进行时频分析,发现在方位角较小时尾波能量较弱而方位角较大时尾波能量较强,尾波中信号的主频在0.1 MHz左右,与前人理论和实验研究结果一致.

     

碳酸盐岩储层缝洞发育带预测:以塔河油田为例

塔河油田碳酸盐岩为古岩溶喀斯特化与受后期构造叠置改造的孔、洞、缝等组成的非均质储层,储层具有规模不同、空间形态不规则、充填性质各异的复杂组合特征以此为对象通过分解地震波场不同特征信号,开发了一系列针对不同储层目标的叠前叠后地震预测技术,不同特征地震预测结果经综合叠置验证分析,实现了残丘体上叠置的孔、洞、缝及古地貌的精细刻画及表征,展示了缝洞空间纵横交错的叠置关系,提高了复杂储层空间展布规律的认识及精确定位。