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991.
笔者等通过电子背散射、二次成像和能谱分析,结合薄片和反射显微镜观察,发现松辽盆地古龙凹陷青山口组页岩中发育了大量由生排烃扩张形成的微米孔和微米缝。生排烃高压扩张微米孔的特点有:①一般只发育在超高压的页岩油储层中;②一般只发育在黏土质长英页岩中,纯黏土岩少见;③多为近圆形或半圆形,直径多在0. 5 μm到数微米,一般1~2 μm,最大可达8 μm;④孔缘一般为以绿泥石为主的黏土,形成不连续的圈环;圈环上缘的黏土多呈弧形或眉状,绿泥石化明显,在背散射图像中呈亮色;⑤孔内多有自生的纳米级葡萄状或豆渣状黏土,是构成封存油气的物质基础;⑥生排烃高压扩张微米孔可以组合成4种类型:即垂向联结成垂直的排烃烟囱型、垂向联结成倾斜的排烃烟囱型、水平联结成顺层的排烃管型和竖面上联结成更大的片状大孔型。排烃烟囱直或微曲,直立或倾斜;宽1~3 μm,最宽可达200 μm;高十几到30 μm,最大可达1500 μm;顶部多与顺层微米缝(或毫米缝)联结,是排烃烟囱的最终泄压和泄油气的总库;生排烃扩张微米孔孔隙度变化大,面孔率一般在5%~6%,局部面孔率最高可达39. 66%。生排烃高压扩张微米缝的特点有:①一般只发育在超高压的页岩油储层中;②一般只发育在黏土质长英页岩中,纯黏土岩少见;③多以顺页理为主的微米缝为主;④略曲的张性缝,多呈锯齿状,绕过刚性矿物;⑤宽度多在0. 5 μm到数十微米;最宽可达150 μm;⑥多与黄铁矿、白云石、磷灰石等自生矿物伴生;⑦多与生排烃扩张微米孔和排烃烟囱相连。生排烃扩张微米孔缝的形成动力主要有两种:一种是烃类流体的高压扩张力;第二种是烃类流体的化学溶蚀力。笔者等计算了形成这种生排烃微米孔和微米缝的压力,形成生排烃扩张微米孔从1500 m的44. 74 MPa到2500 m深的74. 81 MPa;形成生排烃扩张微米缝的排烃压力稍大,在相同深度比形成生排烃扩张微米孔大3 MPa。生排烃扩张微米孔缝与其他孔缝相连构成了一个储运网络,使储层的储集能力和渗透性大幅增加,是可动用储量的主要贡献者,为古龙页岩油的开发创造了有利条件。生排烃扩张微米孔缝的发现对于古龙页岩油的勘探开发具有重要意义,同时对于页岩油储层的研究具有启发作用。 相似文献
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从高压水射流技术在水下工程中应用及高压水射流的作用效应和伤害特征着手,分析影响水下高压水射流作业安全的因素,总结各国制订高压水射流作业的安全标准规程现状,提出制订我国水下高压水射流作业安全规程若干认识和设想。 相似文献
997.
包括恐龙化石在内的古生物化石是重要的地质遗迹,是研究生物进化的最重要资料。该文从物理力学角度,通过数值试验模拟分析围压和轴压作用下对恐龙化石强度和破坏特性的影响效果。试验结果表明:不同埋深时围压对含有不同角度裂隙化石应力影响较大,随着埋深增加,含有裂隙化石的应力大幅增大。在围压与轴压共同作用时,埋深对开裂角的影响较小,而随埋深增大时极限载荷也随之增大。同时,在不同埋深下开裂角随裂隙角度的变化趋势一致,均随着裂隙角度的增大而减小;而极限载荷随裂隙角度的变化趋势一致。 相似文献
998.
AbstractTwo north–south-trending belts of high-temperature–low-pressure (HTLP) sub-regional metamorphism have been identified in the New England Orogen of eastern Australia. Metamorphic complexes in the ~1300?km long Early-Permian Inland belt have ages ca 300–290?Ma, and those of the ~400?km long Mid-Permian Coastal belt ca 275–270?Ma. These periods correspond to the beginning and end of an extended (early–mid Permian) phase of subduction rollback and crustal thinning in eastern Australia. This paper describes and incorporates recent work on the Wongwibinda Metamorphic Complex in the southern New England Orogen as a basis for comparison with thirteen other HTLP sub-regional occurrences within the orogen. These are described in as much detail as is currently available. Some outcrops of HTLP rocks in difficult terrain have been subject to limited study and only conditional comparisons can be made. However, a significant number of characteristics shared between the complexes including: their location at the higher-temperature end of broad areas of very low-grade to greenschist facies metamorphic rocks, indicative of tilted crustal blocks; their association with major shear zones; the presence of migmatite at the high-temperature end of a steep metamorphic field gradient; the presence of two-mica granite formed by the melting of the local sedimentary pile; and temporal association with S-type granites; imply a common extension-related mechanism of formation for these HTLP belts. The connection with major faults and shear zones suggests the belts trace major crustal-scale extensional structures that migrated eastwards from ca 300 to 270?Ma.
- KEY POINTS
Two previously undocumented belts of HTLP subregional metamorphism are identified within the NEO.
Available dating indicates that metamorphism occurred along the belts at the beginning and end of a major early–mid Permian extensional phase in eastern Gondwana/Australia.
The characteristics of the HTLP complexes including their association with shear zones indicates they may delineate major loci of extension.
999.
Traditional consolidation theories cannot provide good predictions of consolidation settlement in land reclamation because of their assumptions that the influence of soil's self-weight is often neglected, and the drainage boundary is considered as fully pervious/impervious. In view of these limitations, an analytical solution is derived for one-dimensional self-weight consolidation problems with a continuous drainage boundary using the finite Fourier sine transform method. Following the classical Terzaghi's small strain theory, the soil's self-weight is considered to produce consolidation settlement in dredged materials with a constant coefficient of consolidation. The continuous drainage boundary can essentially describe the time-dependent variation of drainage capacity at the interface between two adjacent soil layers. By reducing the interface parameters, the effectiveness of the calculation is demonstrated against the Terzaghi's solution. The influence of interface parameters and soil's self-weight stress coefficient on self-weight consolidation is discussed. As expected, the rate of consolidation considering the self-weight stress is faster, although the dependency of consolidation rate on the material property of void ratio is neglected. Moreover, the plane of maximum excess pore-water pressure is estimated as a function of time factor, based on which a design chart is developed to optimize the layout of horizontal drains in land reclamation. 相似文献
1000.
Evangelos Moulas Stefan M. Schmalholz Yury Podladchikov Lucie Taj
manov Dimitrios Kostopoulos Lukas Baumgartner 《Journal of Metamorphic Geology》2019,37(1):1-14
Pressure is one of the most important parameters to be quantified in geological problems. However, in metamorphic systems the pressure is usually calculated with two different approaches. One pressure calculation is based on petrological phase equilibria and this pressure is often termed thermodynamic pressure. The other calculation is based on continuum mechanics, which provides a mean stress that is commonly used to estimate the thermodynamic pressure. Both thermodynamic pressure calculations can be justified by the accuracy and applicability of the results. Here, we consider systems with low‐differential stress (<1 kbar) and no irreversible volumetric deformation, and refer to them as conventional systems. We investigate the relationship between mean stress and thermodynamic pressure. We discuss the meaning of thermodynamic pressure and its calculation for irreversible processes such as viscous deformation and heat conduction, which exhibit entropy production. Moreover, it is demonstrated that the mean stress for incompressible viscous deformation is essentially equal to the mean stress for the corresponding viscous deformation with elastic compressibility, if the characteristic time of deformation is five times longer than the Maxwell viscoelastic relaxation time that is equal to the ratio of shear viscosity to bulk modulus. For typical lithospheric rocks, this Maxwell time is smaller than c. 10,000 years. Therefore, numerical simulations of long‐term (>10 kyr) geodynamic processes, employing incompressible deformation, provide mean stress values that are close to the mean‐stress value associated with elastic compressibility. Finally, we show that for conventional systems the mean stress is essentially equal to the thermodynamic pressure. However, mean stress and, hence, thermodynamic pressure can be significantly different from the lithostatic pressure. 相似文献