Conductivity model for pyrite-bearing laminated and dispersed shaly sands based on a differential equation and the generalized Archie equation

The conductance of pyrite-bearing laminated and dispersed shaly sands is not well understood and resistivity models for pyrite-bearing shaly sands are nonexistent. Thus, we first synthesize clean pyrite-matrix samples, and quartz-matrix samples with variable laminated shale, dispersed shale, and pyrite content and then perform petrophysics experiments to assess the effect of pyrite content on the conductivity of pyrite-bearing shaly sands. Second, based on the differences in conductivity and conduction pathways and geometries because of the variable composition of the pyrite-bearing laminated and dispersed shaly sands, we divide the shaly sands into their components, i.e., laminated shale, quartz grains, pyrite grains, hydrocarbon, dispersed shale, microscopic capillary water, and mobile water. A generalized resistivity model is proposed to describe the conductivity of pyrite-bearing laminated and dispersed shaly sands, based on the combined conductivity differential equation and generalized Archie equation. In the generalized resistivity model, the conductivity differential equation is used to describe the conductivity of dispersed inclusions in a host, whereas the generalized Archie equation is used to describe the conductivity of two conducting phases. Moreover, parallel conductance theory is used to describe the conductivity of dispersed shaly sands and laminated shale. Theoretical analysis suggests that the proposed model satisfies the physical constraints and the model and experimental results agree. The resistivity and resistivity index of shaly sands decrease with increasing conductivity and pyrite. Finally, the accuracy of the resistivity model is assessed based on experimental data from 46 synthetic core samples with different oil saturation. The model can describe the conductivity of clean pyrite-matrix samples, and quartz-matrix samples with different volumes of laminated shale, dispersed shale, and pyrite. An accurate saturation model of pyrite-bearing laminated and dispersed shaly sands is thus obtained and the log data interpretation in complex shaly sands can improve with the proposed model.     

Acoustic reflection well logging modeling using the frequency-domain finite-element method with a hybrid PML

In this paper, we propose a hybrid PML (H-PML) combining the normal absorption factor of convolutional PML (C-PML) with tangential absorption factor of Mutiaxial PML (M-PML). The H-PML boundary conditions can better suppress the numerical instability in some extreme models. and the computational speed of finite-element method and the dynamic range are greatly increased using this HPML. We use the finiteelement method with a hybrid PML to model the acoustic reflection of the interface when wireline and well logging while drilling (LWD), in a formation with a reflector outside the borehole. The simulation results suggests that the PS- and SP- reflected waves arrive at the same time when the inclination between the well and the outer interface is zero, and the difference in arrival times increases with increasing dip angle. When there are fractures outside the well, the reflection signal is clearer in the subsequent reflection waves and may be used to identify the fractured zone. The difference between the dominant wavelength and the model scale shows that LWD reflection logging data are of higher resolution and quality than wireline acoustic reflection logging.     

Structural strength deterioration of coastal bridge piers considering non-uniform corrosion in marine environments

In the aggressive marine environment over a long-term service period,coastal bridges inevitably sustain corrosion-induced damage due to high sea salt and humidity.This paper investigates the strength reduction of coastal bridges,especially focusing on the effects of non-uniform corrosion along the height of bridge piers.First,the corrosion initiation time and the degradation of reinforcement and concrete are analyzed for bridge piers in marine environments.To investigate the various damage modes of the concrete cover,a discretization method with fiber cells is used for calculating time-dependent interaction diagrams of cross-sections of the bridge piers at the atmospheric zone and the splash and tidal zone under a combination of axial force and bending moment.Second,the shear strength of these aging structures is analyzed.Numerical simulation indicates that the strength of a concrete pier experiences dramatic reduction from corrosion initiation to the spalling of the concrete cover.Strength loss in the splash and tidal zone is more significant than in the atmospheric zone when structures’service time is assumed to be the same.     

Rupture model of the 2013 M_W 6.6 Lushan (China) earthquake constrained by a new GPS data set and its effects on potential seismic hazard

Vertical records are critically important when determining the rupture model of an earthquake, especially a thrust earthquake. Due to the relatively low fitness level of near-field vertical displacements, the precision of previous rupture models is relatively low, and the seismic hazard evaluated thereafter should be further updated. In this study, we applied three-component displacement records from GPS stations in and around the source region of the 2013 MW6.6 Lushan earthquake to re-investigate the rupture model.To improve the resolution of the rupture model, records from both continuous and campaign GPS stations were gathered, and secular deformations of the GPS movements were removed from the records of the campaign stations to ensure their reliability. The rupture model was derived by the steepest descent method(SDM), which is based on a layered velocity structure. The peak slip value was about 0.75 m, with a seismic moment release of 9.89 × 10~(18) N·m, which was equivalent to an M_W6.6 event. The inferred fault geometry coincided well with the aftershock distribution of the Lushan earthquake. Unlike previous rupture models, a secondary slip asperity existed at a shallow depth and even touched the ground surface. Based on the distribution of the co-seismic ruptures of the Lushan and Wenchuan earthquakes, post-seismic relaxation of the Wenchuan earthquake, and tectonic loading process, we proposed that the seismic hazard is quite high and still needs special attention in the seismic gap between the two earthquakes.     

江西相山酸性火山-侵入杂岩精确年代学与演化序列研究

相山火山盆地主体岩石为一套由熔结凝灰岩、流纹英安岩、流纹英安斑岩、碎斑熔岩、粗斑花岗斑岩及似斑状花岗岩组成的酸性火山-侵入杂岩体, 构成了两个完整的喷发-溢流(侵出)-侵入的岩浆活动亚旋回。本文在野外地质调查的基础上, 采用SIMS、LA-ICP-MS技术对主要岩类进行了高精度的锆石U-Pb年代学研究, 并建立了火山-侵入杂岩体的演化序列。结果表明, 打鼓顶组熔结凝灰岩代表了相山火山-侵入活动的最早期产物, 其锆石U-Pb年龄为140.7±2.7 Ma、140.1±1.8 Ma和138.2±1.6 Ma, 第一亚旋回主体流纹英安岩的锆石U-Pb年龄135.0±1.8 Ma。鹅湖岭组熔结凝灰岩代表了火山-侵入活动的第二亚旋回的开始, 其U-Pb年龄为135.6±1.2 Ma, 第二亚旋回主体碎斑熔岩的锆石U-Pb年龄133.6±1.3 Ma, 沙洲单元的粗斑花岗斑岩和似斑状花岗岩属于该亚旋回最晚期的侵入岩, 其锆石U-Pb年龄代表了相山火山-侵入活动的结束时间(分别为133.4±1.2 Ma和133.9±1.1 Ma)。相山早白垩世火山-侵入活动延续时间较短, 整体上呈现一个连续的过程, 初始时间在141 Ma附近, 结束时间在132 Ma左右。概言之, 第一亚旋回(141~135 Ma)以形成熔结凝灰岩、流纹英安岩和流纹英安斑岩为主, 第二亚旋回(135~132 Ma)以熔结凝灰岩、碎斑熔岩、粗斑花岗斑岩和似斑状花岗岩为主。岩石地球化学和野外地质特征也与两个亚旋回火山-侵入岩浆活动相吻合。     

山东招掖金矿带原生金矿化地球化学特征的数学地质研究

本文主要是应用数学地质方法研究山东招掖金矿带原生金矿化地球化学特征,从而确定金矿化的最佳地球化学标志组合,并建立原生金矿化模式及金矿体原生晕的判别模式.     

Assessment and zonation of storm surge hazards in the coastal areas of China

Natural Hazards - Coastal inundation due to storm tides is computed using ADvanced CIRCulation (ADCIRC) model along the east coast of India. Inland inundation due to storm tides is calculated every...     

An experimental approach for determination of the Weibull homogeneity index of rock or rock-like materials

Acta Geotechnica - The spatial variation of the physical–mechanical properties of rock or rock-like materials is an intrinsic characteristic of the materials induced by multiscale material...     

非点源污染的流域分配方法研究

农业非点源污染的流域分配研究对于提高环境质量具有重要的现实意义。根据遥感技术得到的土地利用类型、河网、道路、圩区等信息,结合地理信息系统（GIS）的空间分析功能,对非点源污染负荷进行了定量计算及可视化分析,在此基础上,得到各主要河段的污染分配量,这可为寻求流域内合理的土地利用模式和农业非点源污染排放总量的控制方法提供决策依据。     

T形截面柱的非线性分析

编制了适用于任意截面的钢筋混凝土压弯构件截面的弯矩—曲率非线性分析程序。在此基础上,计算了考虑非线性变形的异形柱弯矩—曲率关系,并研究了翼缘、轴压比等因素对异形柱强度和延性的影响,可作为异形柱研究的参考依据。