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991.
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. 相似文献
992.
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. 相似文献
993.
鲁甸6.5级地震地下流体典型异常与前兆机理分析 总被引:2,自引:1,他引:1
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。 相似文献
994.
介绍Locata伪距和载波相位单点定位的方法。通过仿真数据和试验,分析基准站个数对定位精度的影响,比较伪距定位和观测值组合定位的精度,验证了载波相位定位结果的稳定性。分析表明,Locata静态单点定位的精度可以达到cm~mm级。 相似文献
995.
996.
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。 相似文献
997.
998.
地壳流体对地震活动的影响与控制作用 总被引:2,自引:0,他引:2
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。 相似文献
999.
In the water flooding of mixed-wet porous media, oil may drain down to relatively low residual oil saturations (Sor). Various studies have indicated that such low saturations can only be reached when oil layers in pore corners are included in the pore-scale modelling. These processes within a macroscopic porous medium can be modelled at the pore-scale by incorporating the fundamental physics of capillary dominated displacement within idealised pore network models. Recently, the authors have developed thermodynamic criteria for oil layer existence in pores with non-uniform wettability which takes as input geometrically and topologically representative networks, to calculate realistic Sor values for mixed-wet and oil-wet sandstones [16, 21]. This previous work is developed in this paper to include (i) the visualisation of the 3D structure of this residual oil, and (ii) a statistical analysis of this “residual/remaining” oil. Both the visualisation and the statistical analysis are done under a wide range of wettability conditions, which is reported for the first time in this paper.The structure of residual oil for strongly water wet systems is well known (where residual = remaining oil) and our model agrees with this but this structure changes radically for mixed wet systems (where residual ≠ remaining) and this has not yet been visualised experimentally. We find that for more water-wet systems high final residual oil saturations are reached at relatively small amounts of water injected and this oil is present in the pores as bulk oil. On the other hand, for more oil-wet systems we find a slow decrease of the amount of remaining oil with increasing amounts of injected water. During the process, the remaining connectivity of the oil phase is increasingly provided by oil layers only, hence the slow drainage. The final residual oil saturation, only reached in the theoretical limit of an infinite amount of injected water, is almost entirely contained in large number of (relatively low volume) oil layers, which are present in pores of most radius sizes. 相似文献
1000.
Oblique wave scattering by undulating porous bottom in a two-layer fluid: Fourier transform approach
Srikumar Panda 《地球物理与天体物理流体动力学》2014,108(6):587-614
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. 相似文献