On the pore‐scale mechanisms leading to brittle and ductile deformation behavior of crystalline rocks

Deformation mechanisms at the pore scale are responsible for producing large strains in porous rocks. They include cataclastic flow, dislocation creep, dynamic recrystallization, diffusive mass transfer, and grain boundary sliding, among others. In this paper, we focus on two dominant pore‐scale mechanisms resulting from purely mechanical, isothermal loading: crystal plasticity and crofracturing. We examine the contributions of each mechanism to the overall behavior at a scale larger than the grains but smaller than the specimen, which is commonly referred to as the mesoscale. Crystal plasticity is assumed to occur as dislocations along the many crystallographic slip planes, whereas microfracturing entails slip and frictional sliding on microcracks. It is observed that under combined shear and tensile loading, microfracturing generates a softer response compared with crystal plasticity alone, which is attributed to slip weakening where the shear stress drops to a residual level determined by the frictional strength. For compressive loading, however, microfracturing produces a stiffer response than crystal plasticity because of the presence of frictional resistance on the slip surface. Behaviors under tensile, compressive, and shear loading invariably show that porosity plays a critical role in the initiation of the deformation mechanisms. Both crystal plasticity and microfracturing are observed to initiate at the peripheries of the pores, consistent with results of experimental studies. Copyright © 2015 John Wiley & Sons, Ltd.     

煤中显微裂隙的成因类型及其研究意义

分析、归纳了大量的扫描电子显微镜观测结果，以煤岩学、构造地质学研究为基础，依据煤中显微裂隙的形态，大小、排列组合等发育特征，将内生裂隙进一步划分为失水裂隙，缩聚裂隙、静压裂隙，将外生裂隙进一步划分为张性裂隙，压性裂隙，剪性裂隙，松弛裂隙，描述了各类隙的发育特征，探讨了裂隙的演化，识别和影响裂隙发育的因素，裂隙成因类型的研究，有助于判断不同裂隙对煤储层渗透率的贡献。     

松辽盆地南部红岗油田青山口组砂岩中片钠铝石的形成温度

主要以松辽盆地南部红岗油田富含片钠铝石砂岩的红143和红146井为研究对象,通过普通薄片鉴定、茜素红-S染色、扫描电镜、能谱分析、显微测温等分析方法,对研究区含片钠铝石砂岩的成岩共生序列,尤其是流体包裹体均一温度进行了详细的研究.红岗油田成岩共生序列为:黏土矿物→石英次生加大边→方解石→片钠铝石→铁白云石→石英愈合微裂...     

扫描电子显微镜对花岗岩中主要矿物裂隙作用的研究

微裂隙对于岩石的物理性质有重要影响.通过光学显微镜对显微裂隙进行的观察,难以将薄片的制作过程中产生的裂隙同自然裂隙区分;其次,观测的裂隙大小限制在0.1mm或以上数量级,一些重要细节观察不到.扫描电镜的高放大倍数和三维分辨率使其成为适合于裂隙研究的理想工具.利用扫描电镜观测了浙江花岗岩在室温下由51.6MPa压力产生的裂隙的发育过程.观察花岗岩的表面以研究其微裂隙和矿物的解理、晶形及破裂作用.微裂隙分为3种类型:晶体内裂隙(完全发育在颗粒内部),晶体间裂隙(穿过颗粒边界进入其他颗粒中),颗粒边界裂隙(沿颗粒边界发育或与边界重合).本研究中的花岗岩为中-粗粒(1~6mm),经过蚀变,约含40%斜长石,25%钾长石,25%石英,10%镁铁矿物(主要为黑云母和白云母).     

鄂尔多斯盆地延长组超低渗透砂岩储层微观孔隙结构特征研究

通过物性分析、扫描电镜、铸体薄片、高压压汞技术对鄂尔多斯盆地延长组沿25、庄40、庄19三个区块超低渗透砂岩储层样品进行分析测试,研究其微观孔隙结构特征。研究表明,超低渗透砂岩储层岩石孔隙结构非均质性强,孔隙喉道类型多样是储层渗透性差的主要原因;孔喉分选系数在2.0~2.5之间、变异系数在0.1~0.2之间物性较好;较大孔喉是决定和改善储层渗透性的重要因素,细小孔道对储层储集能力的贡献较大,储层微裂缝较为发育。储层物性参数的差异、孔喉特征参数的差异等,均归因于微观孔隙结构的差异。     

基于地震资料的小断裂检测技术

煤矿安全生产的形势越来越严峻,查明煤层的构造发育情况,特别是小断层及微断裂的发育情况,是目前煤炭工业迫待解决的一大难题。根据煤田中小断层和断面波的特征,有针对性的提出了小断层高分辨率时频谱处理识别技术和基于断面波特征的微断裂识别方法,模型试验和实际地震资料的应用表明,该方法能够充分挖掘地震资料的有效信息,较好的识别出煤田中的小断层和微断裂。     

Occurrence characteristics and controls over mobile fluids in a tight sandstone reservoir

Using nuclear magnetic resonance (NMR) technology, this paper proposes a new pore structure parameter called ‘effective mobile fluid saturation’, which can account for two factors that influence mobile fluids in pores: the stiction of hydrophilic particulates on the surfaces of pores and the constraints of tiny throats. The new parameter quantifies the effective content of the mobile fluids and compensates for the deficiencies using conventional parameters like ‘mobile fluid saturation’. Pore-throat connectivity is crucial for effective mobile fluid saturation, which reaches its highest point when the sorting coefficient is in the range of 1.5–2.0. Recognition of the pore-throat configuration is crucial in assessing the effectiveness of mobile fluids in tight sandstone reservoirs. Factors that influence the effectiveness of mobile fluids in three types of pore structures are discussed from a diagenetic perspective, including the development of microfractures and secondary pores, recrystallisation, clay mineral precipitation, and other micropore structure characteristics.     

地震孕育状态的地面物理测度--兼论研究方法问题

论述了地震孕育状态的地面物理测度问题，举出了两个地面物理测度的例子：地震活动性，微破裂导致的介质的各向异性；论述了实验在震源物理研究中的地位等问题。     

Anisotropic Variation Law of Rock Permeability with the Burial Depth of Limestone

Permeability tensors of both macrofracture and microfracture systems were measured progressively along the depth of limestone formations at severed sites. It was found that the principal permeability values KX, Ky and Kz in these permeability tensors all decrease simultaneously and logarithmically with depth. However, the limestone aquifers are composed of an upper region where the larger permeability ellipsoid is upright or prolate and characterized by Kz>Kx and Kz>Ky, a transitional zone, and a lower zone whose smaller permeability ellipsoid is horizontal or oblate and characterized by KZmicrofracture system. It is next to impossible to examine the rock permeability tensor of the aquifer just by meas     

岩石变形实验中的微破裂与地震的联想

根据室内岩石变形实验中岩石的微破裂和应变能释放等情况，联想到地震发生的几种相似现象：（１）岩体在较低的状态下亦有可能发生地震；（２）小震的发生预示岩体内应变和应变能的释放，但应力却未必释放；（３）主震时就变能大量释放，但仍有相当多的应变能残留在岩体中，这应是老震区发生地震的原因之一。