南极洲纳尔逊冰帽的某些动力学特征*

纳尔逊冰帽是南设得兰群岛的一个小冰帽,受海洋性气候影响冰帽上降水丰富,冰温较高。冰帽表面运动速度完全由冰帽表面形态和冰帽底床形态所控制,其中E剖面更为复杂。冰帽驱动应力基本小于100kPa.由V/Z～Za曲线得到在V/7为0.6～3×10^-9范围内的流动参数:n约为1;B≈4.3×10¹⁰dynescm^-2sec.这表明在低应力区,冰体流动更接近牛顿流体。     

不同围压和流体饱和状态下致密砂岩弹性各向异性特征

为研究致密砂岩声波速度及其各向异性随围压的变化规律以及不同流体饱和状态下的弹性各向异性特征,钻取了不同方向的岩心并在实验室超声波频率下对致密砂岩的声学特性进行了测量,分别给出干燥和饱和水状态下,不同方向样品纵横波速度、刚性系数以及各向异性系数随围压的变化规律,并对实验结果进行了分析讨论.实验结果表明致密砂岩纵横波速度、纵横波速度比以及刚性系数均随围压增加而增加,但其在不同饱和状态下的变化率却截然不同;纵横波速度比、各向异性系数在饱和水状态下变化规律不明显,表明孔隙流体的存在对于岩石物理性质有着非常重要的影响.这方面的实验工作不但对于考察不同流体性质对致密岩石弹性各向异性影响是必要的,而且有助于致密砂岩油水和气层的识别.     

Comparison of P‐wave attenuation models of wave‐induced flow

Wave‐induced oscillatory fluid flow in the vicinity of inclusions embedded in porous rocks is one of the main causes for P‐wave dispersion and attenuation at seismic frequencies. Hence, the P‐wave velocity depends on wave frequency, porosity, saturation, and other rock parameters. Several analytical models quantify this wave‐induced flow attenuation and result in characteristic velocity–saturation relations. Here, we compare some of these models by analyzing their low‐ and high‐frequency asymptotic behaviours and by applying them to measured velocity–saturation relations. Specifically, the Biot–Rayleigh model considering spherical inclusions embedded in an isotropic rock matrix is compared with White's and Johnson's models of patchy saturation. The modeling of laboratory data for tight sandstone and limestone indicates that, by selecting appropriate inclusion size, the Biot‐Rayleigh predictions are close to the measured values, particularly for intermediate and high water saturations.     

我国地震地下流体观测台网调整与优化方案探讨

本文首先简要介绍了我国地震地下流体观测台网的现状,然后针对其存在的主要问题提出了调整与优化的建议: ① 调整布局,重点加强我国中西部地区(105°E以西)的监测; ② 扩大规模,观测井(泉)数要达到1000个左右; ③ 全面提高观测井质量,淘汰不符合规范要求的观测井(泉),改造不完全符合规范要求的观测井,新建一批完全符合规范的观测井; ④ 优化观测项目的组合,大力发展观测井(泉)水流量观测,强化以H₂、 He、 CO₂等为主测项的断层带土壤气观测,建立断层带土壤气观测网; ⑤ 优化现有的观测模式,开展平面上的台阵式观测与垂向的多层次立体化观测; ⑥ 完善与提升现有数字化观测技术水平.      

鲁甸6.5级地震地下流体典型异常与前兆机理分析

基于川滇地区前兆台网资料,结合异常现场核实工作结果,对鲁甸6.5级地震前的地下流体异常现象进行了总结。遵循地震分析预报的基本思路,按照长期、中期、短期趋势异常、临震异常和宏观异常阐述了鲁甸6.5级地震前地下流体典型异常现象。结果表明,长期和中期趋势背景异常主要出现在距震中300~500km范围,短期趋势和临震及宏观异常集中于震中区100km范围内。这种流体异常特征反映了在较高密度的观测点区域,可以观测到流体活动加剧的前兆现象,有利于判定地震危险区和短期阶段跟踪分析。区域应力加载作用可能引起的断裂带裂隙的开启与闭合,导致温泉和井水温、深部气体与承压井水位的持续变化;水岩反应加剧和地下水混合作用增强,使地下水离子组分浓度发生变化,甚至导致显著宏观异常。在一定密度的前兆观测地区,能够获取用于判定地震危险性的前兆信息。     

压裂液在煤层中的运移模拟研究

为给山西省临县三交区块的地下水环境保护提供科学依据,运用地下水数值模拟技术对压裂液在煤层中的运移进行了预测。在分析研究区地质结构的基础上,建立了水文地质概念模型,将山西组3^#煤层概化为一个承压含水层,其上覆二叠系砂岩、泥岩作为隔水层,下伏的泥岩、砂岩互层作为隔水层,并确定了地下水系统的边界条件。运用地下水模型软件(Feflow)对研究区内的压裂液在煤层中的运移进行了模拟和预测,预测结果表明,压裂液在煤层中的的运移范围在煤层压裂影响范围以内,即压裂井周围300 m范围内。     

致密砂岩气藏可动流体赋存特征的微观地质因素: 以苏里格气田东部盒8段储层为例

以苏里格气田东部盒8段典型的致密砂岩气藏为例,运用核磁共振、恒速压汞、铸体薄片、物性、X-衍射等实验资料,探讨了影响可动流体赋存差异的微观地质 因素。结果表明,盒8段储层可动流体饱和度低,T₂谱分布均为左高峰右低峰的双峰态;黏土矿物的充填与孔隙类型是孔隙结构复杂的重要因素,孔隙结构是影响可动流体赋存特征的关键;面孔率、喉道 半径、孔喉半径比是影响可动流体饱和度的主要因素,有效孔隙体积、分选系数对可动流体饱和度影响明显,储层物性、黏土矿物、有效喉道体积、孔隙半径对可动流体饱和度影响较弱。     

煤层气井流体原位实时监测仪

煤层气生产过程中,需要随时了解和掌握煤层气井的产水、产气、液面高度等各项参数,以便根据生产阶段的需要及时调整生产参数,使煤层气井的生产处于最佳状态。目前国内煤层气抽采过程中仅能单独测量压力、温度、液位等参数,并不能检测每个层位的产气产水量,因此为了达到长期同时监测不同层位煤层的目的,设计了煤层气井流体原位实时监测仪。该监测仪不仅能测量温度、压力等参数,还可结合地面测得的气、水流量,分别得出不同层位煤层的产气产水量,为煤层气开采方法的确定提供科学依据,有利于提高煤层气抽采率。      

地壳流体对地震活动的影响与控制作用

地壳中普遍存在着流体,不仅在地壳动力过程中发挥重要作用,而且也极有可能在地震孕育与发生过程中起着不为人知的重要作用。这样的认识,越来越得到地质学家与地球物理学者们的认可。本文概括介绍了地壳流体对地震活动的空间分布、震源深度与强震活动周期的影响与控制作用,并提出了地壳硬夹层孕震与流体促震的假设。最后还介绍了通过流体控制地震活动并实现减轻地震灾害的思想。     

Oblique wave scattering by undulating porous bottom in a two-layer fluid: Fourier transform approach

The problem involving scattering of oblique waves by small undulation on the porous ocean bed in a two-layer fluid is investigated within the framework of linearised theory of water waves where the upper layer is free to the atmosphere. In such a two-layer fluid, there exist waves with two different wave numbers (modes): wave with lower wave number propagates along the free surface whilst that with higher wave number propagates along the interface. When an oblique incident wave of a particular mode encounters the undulating bottom, it gets reflected and transmitted into waves of both modes so that some of the wave energy transferred from one mode to another mode. Perturbation analysis in conjunction with Fourier transform technique is used to derive the first-order corrections of velocity potentials, reflection and transmission coefficients at both modes due to oblique incident waves of both modes. One special type of undulating bottom topography is considered as an example to evaluate the related coefficients in detail. These coefficients are shown in graphical forms to demonstrate the transformation of water wave energy between the two modes. Comparisons between the present results with those in the literature are made for particular cases and the agreements are found to be satisfactory. In addition, energy identity, an important relation in the study of water wave theory, is derived with the help of the Green’s integral theorem.