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1.
针对龙门石窟灰岩水溶液侵蚀破坏现象,考虑石窟区的泉水、石窟渗水和雨水的化学成分,配置不同的化学溶液,研究不同化学溶液作用下龙门石窟灰岩的力学损伤特性及化学溶解行为。通过不同化学溶液侵蚀不同时间下灰岩的力学试验及分析,获得不同化学溶液侵蚀下龙门石窟灰岩强度损伤特性,建立化学溶液作用下灰岩单轴抗压强度随时间的侵蚀损伤方程。通过不同化学溶液侵蚀不同时间下灰岩溶解动力学试验及分析,研究灰岩在不同化学溶液中的溶解特性,建立化学溶液作用下灰岩侵蚀溶解动力学方程。试验分析研究表明,由于水化学溶液的溶解作用,化学溶液侵蚀下灰岩强度均有所下降。盐效应、同离子效应对灰岩溶解速率和强度的影响较大。盐效应提高灰岩溶解速率,同离子效应降低灰岩溶解速率。盐的种类和浓度均相同时,酸性越强,溶解速率越大;盐的种类和pH值相同时,盐浓度升高,灰岩溶解速率增大。研究结果将为石质文物及岩石工程的长期保护提供重要的理论基础,具有广泛的实际工程应用价值和应用前景。 相似文献
2.
3.
Temperature changing in soil has an influence on the redistribution of water and salt. With constant temperature in an open
system we performed two unidirectional freezing tests with different temperature settings of clay collected at Beiluhe test
site along Qinghai–Tibet Railway. The groundwater supply of the soil was simulated during the experiments by attaching a liquid
replenishment system to the bottom of the sample container. Water content and ions content of the soil were measured after
the experiments. By analyzing the two main ions in the soil we obtained the laws and the properties of water and salt redistribution
during freezing of clay soil. The results show that the water content increases in freezing section while it decreases in
unfrozen section compared with initial water content. To the salt, under this circumstance the diffusion due to the concentration
gradient dominated the transfer way in clay soil, so the ions content in the unfreezing section decreased with the decreasing
of the distance to freezing front. At the ice segregation layer the ions content is less due to the ice self-purification,
and almost nothing changed in frozen section. 相似文献
4.
A Fully Coupled Chemo-Poroelastic Analysis of Pore Pressure and Stress Distribution around a Wellbore in Water Active Rocks 总被引：1，自引：0，他引：1
Water active rocks consist of minerals that hold water in their crystalline structure and in pore spaces. Free water from
drilling fluid can be attracted by the formation depending on the potential differences between pore space and drilling fluid.
The fluid movement into the formation or out of the formation can lead to a change in effective stress, thus causing wellbore
failures. In all previous studies it is found that the solute transport from or to the formation is primarily controlled by
diffusion process and the effect of advection on solute transfer is negligible for a range of very low permeable shale formations
(>10−5 mD). In this study a range of permeable shale formations (10−5 to 10−3 mD) commonly encountered in drilling oil and gas wells are considered to investigate the solute transfer between drilling
fluid and formation due to advection. For this purpose a finite element model of fully coupled chemo-hydro-mechanical processes
was developed. Results of this study revealed that the solute transfer between the drilling fluid and the shale formation
is controlled primarily by permeability of the shale formations. For the range of shale formations studied here, there exists
a threshold permeability below which the solute transfer is dominated by diffusion process and above which by fluid in motion
(fluid flow). Results from the numerical experiments have shown that when the permeability of shales is greater than this
threshold permeability, the chemical potential gradient between the pore fluid and drilling fluid reaches equilibrium faster
than that when the permeability of shales is below this threshold value. Also it has been found that when advection is taken
into account, effective radial and tangential stresses decrease around the wellbore, particularly near the wellbore wall where
the solute concentration has reached near equilibrium. 相似文献
5.
页岩中含有一定量的黏土矿物，在与水基压裂液接触后会表现出与泥岩相同的膨胀特性和强度弱化效应，进而引起套管外载增加，在页岩储层压裂过程中套管出现不同程度的变形问题。以渝东北地区龙马溪组页岩为研究对象，开展不同溶液体系下页岩的自吸、膨胀特性物理实验，分析页岩水化对其岩石力学特性的影响。结果表明:页岩吸水量与时间呈对数递增关系，在不同溶液体系中，吸水量大小表现为蒸馏水 > 地层水 > 滑溜水，含有减阻剂浓度小的滑溜水体系更利于减弱页岩的吸水能力；页岩膨胀率与时间呈逐渐增长趋势，黏土矿物含量、围压和溶液体系对页岩膨胀率影响明显，相对于黏土含量，围压对膨胀率影响更加明显，页岩在溶液体系中的膨胀性能表现为蒸馏水 > 地层水 > 滑溜水；页岩的抗压强度和弹性模量都随着水化时间的增加整体呈线性递减规律。研究结果对完井过程套管强度设计具有一定的指导意义。 相似文献
6.
《Geomechanics and Geoengineering》2013,8(3):167-178
Wellbore instability, particularly in shale formations, is regarded as a major challenge in drilling operations. Many factors, such as rock properties, in-situ stresses, chemical interactions between shale and drilling fluids, and thermal effects, should be considered in well trajectory designs and drilling fluid formulations in order to mitigate wellbore instability-related problems. A comprehensive study of wellbore stability in shale formations that takes into account the three-dimensional earth stresses around the wellbore as well as chemical and thermal effects is presented in this work. The effects of borehole configuration (e.g. inclination and azimuth), rock properties (e.g. strength, Young's modulus, membrane efficiency and permeability), temperature and drilling fluid properties (e.g. mud density and chemical concentrations) on wellbore stability in shale formations have been investigated. Results from this study indicate that for low-permeability shales, chemical interactions between the shale and water-based fluids play an important role. Not only is the activity of the water important but the diffusion of ions is also a significant factor for saline fluids. The cooling of drilling fluids is found to be beneficial in preventing compressive failure. However, decreasing the mud temperature can be detrimental since it reduces the fracturing pressure of the formation, which can result in lost-circulation problems. The magnitude of thermal effects depends on shale properties, earth stresses and wellbore orientation and deviation. Conditions are identified when chemical and thermal effects play a significant role in determining the mud-weight window when designing drilling programmes for horizontal and deviated wells. The results presented in this paper will help in reducing the risks associated with wellbore instability and thereby lowering the overall non-productive times and drilling costs. 相似文献
7.
Weathering of the New Albany Shale, Kentucky, USA: I. Weathering zones defined by mineralogy and major-element composition 总被引：1，自引：1，他引：0
Comprehensive understanding of chemical and mineralogical changes induced by weathering is valuable information when considering the supply of nutrients and toxic elements from rocks. Here minerals that release and fix major elements during progressive weathering of a bed of Devonian New Albany Shale in eastern Kentucky are documented. Samples were collected from unweathered core (parent shale) and across an outcrop excavated into a hillside 40 year prior to sampling. Quantitative X-ray diffraction mineralogical data record progressive shale alteration across the outcrop. Mineral compositional changes reflect subtle alteration processes such as incongruent dissolution and cation exchange. Altered primary minerals include K-feldspars, plagioclase, calcite, pyrite, and chlorite. Secondary minerals include jarosite, gypsum, goethite, amorphous Fe(III) oxides and Fe(II)-Al sulfate salt (efflorescence). The mineralogy in weathered shale defines four weathered intervals on the outcrop—Zones A–C and soil. Alteration of the weakly weathered shale (Zone A) is attributed to the 40-a exposure of the shale. In this zone, pyrite oxidization produces acid that dissolves calcite and attacks chlorite, forming gypsum, jarosite, and minor efflorescent salt. The pre-excavation, active weathering front (Zone B) is where complete pyrite oxidation and alteration of feldspar and organic matter result in increased permeability. Acidic weathering solutions seep through the permeable shale and evaporate on the surface forming abundant efflorescent salt, jarosite and minor goethite. Intensely weathered shale (Zone C) is depleted in feldspars, chlorite, gypsum, jarosite and efflorescent salts, but has retained much of its primary quartz, illite and illite–smectite. Goethite and amorphous FE(III) oxides increase due to hydrolysis of jarosite. Enhanced permeability in this zone is due to a 14% loss of the original mass in parent shale. Denudation rates suggest that characteristics of Zone C were acquired over 1 Ma. Compositional differences between soil and Zone C are largely attributed to illuvial processes, formation of additional Fe(III) oxides and incorporation of modern organic matter. 相似文献
8.
Osmotic phenomena refer to water and solute transport processes that occur when transport of solute molecules or ions is restricted by the porous medium relative to that of water molecules. Chemical osmosis and reverse osmosis/ultrafiltration are osmotic phenomena. The studies of “coupled flow” caused by chemical osmosis have been widely applied in many fields, such as earth science, environmental science and civil engineering. This paper provided a review of the considerable advances in the field of chemical osmosis and clay semipermeable membrane since the 1950s. We summarized the research progress of chemical osmosis in clayey sediments into three aspects: theoretical basis, experimental research and numerical model. In particular, the laboratory equipment and measurement methods of the chemico-osmotic efficiency coefficient σ were described,. The existing discontinuous models based on the ‘diffusive double layer’ theory were summerized, as well as the various control factors of σ. It increases with Cation Exchange Capacity (CEC), compaction pressure and decreases by the increasing of porosity and solution concentration. This paper also summerized the contimuum models based on non-equilibrium thermodynamics, which are used to explain and predict anomalies of hydraulic head pressure and salinity in clayey environments. For the future development of this discipline, it is critical to find a reliable method to confirm the σ value. It is also critical to emphasize the research on chemical osmosis in complex conditions and the influence of chemical osmosis on groundwater flow and solute transpotation. China has just stepped into this research area and more efforts should be made if significant progress is desired. This review will be helpful to further research on groundwater numerical simulation integrated with chemical osmosis in China. 相似文献
9.
《Geomechanics and Geoengineering》2013,8(3):178-184
ABSTRACTWellbore instability is one of the major challenges facing the drilling industry and it shows itself in the form of wellbore collapse and/or fracture. The major reason for this challenge is the inability of the mud density to balance the weight of the excavated materials. While most drilling operations are carried out through shale formations, the complexities of drilling such wells are increased because of the tendency for shale to react with water-based mud. Moreover, the very low permeability of shale means that time-dependent effects may set in. The convention used to incorporate time-dependent effect is to couple the constitutive stress model and chemical diffusion, but in this study, we considered the effect of incorporating time variable into the rock failure criterion. The choice criterion used is the Mogi-Coulomb rock failure criterion, which was modified to incorporate the time effect. The results indicate that in an open-hole the mud density to prevent wellbore collapse increases with time while that to prevent wellbore fracture decreases, thus making the mud window reduce with time. 相似文献
10.
The through-diffusion of HTO, 22Na+ and 36Cl− in kaolinite, homo-ionic Na-illite and homo-ionic Na-montmorillonite was measured at a high degree of compaction as a function of the salt concentration in the ‘external solution’, i.e. in the solution in contact with the clay sample. The clays were chosen for this study because of their differences in the number and nature of ion exchange sites leading to different proportions of interlayer-, inter-particle and free pore water. It was found that the diffusive mass transfer of Na+ in Na-montmorillonite and Na-illite increased with decreasing external salt concentration, while the opposite trend was observed for the diffusion of Cl−. These trends are more pronounced in the case of Na-montmorillonite than in Na-illite, while almost no salt effect was observed for kaolinite. Similarly no salt effect was observed for the diffusion of HTO through all of the clays tested. These observations are in agreement with a conceptual model where it is assumed that cations diffuse preferentially in the interlayer or diffuse double-layer porosity, while anions are almost completely excluded from these regions. In the case of Na+ diffusion, the salt effects can be explained by an influence on the concentration gradient of diffusing cations, while in the case of Cl− the external salt concentration has an effect on the accessible porosity. Effective diffusion coefficients of Cl− fulfil the same relationship to porosity as those of the uncharged HTO, when using accessible porosities for such a comparison. Furthermore it is shown that pore diffusion coefficients for the three tracers are fairly well correlated with the respective diffusion coefficients in bulk water, if the effective diffusion coefficients for Na+ are derived from calculated tracer concentration gradients in the interlayer or diffuse double-layer porosities. 相似文献
11.
In the present work, the relationship between intrinsic factors, mechanical properties and durability of Miocene sandstones used in the architectural heritage of Tunisia, specifically in the Roman aqueduct of Oued Miliane and Uthina site, are studied. The petrographic study and the characterisation of porous network have been carried out using optical microscopy, mercury intrusion porosimetry and laser scanner confocal microscopy (LSCM). The hygric behaviour has also been determined from water absorption under vacuum, drying, capillary water absorption and water vapour permeability. The mechanical properties have been assessed from compressive strength and abrasion tests. Rock durability has been evaluated from salt crystallization (sodium sulphate) accelerated aging tests. The results show good hygric behaviour characterised by a high evaporation rate and almost no retention of water; due to the macroporous character of the rock and the good connectivity of the pore network. Because of the poor lithification, the stone has a very low mechanical strength which makes it very vulnerable to the salt crystallization effects. The absence of chemically unstable minerals preserves the rock from chemical alteration. The durability of the building stone is mainly conditioned by salt loading of the monument. 相似文献
12.
Adsorption of copper and zinc by oil shale 总被引：8，自引：0，他引：8
Oil shale is able to remove appreciable amounts of copper and zinc ions from aqueous solutions. It was noted that an increase
in the adsorbent concentration with constant copper or zinc concentration resulted in greater metal removal from solution.
An increase in the copper or zinc concentration with a constant sorbent concentration resulted in higher metal loading per
unit weight of sorbent. For both metals, copper and zinc, equilibrium was attained after 24-h contact time. Increase in the
initial pH or temperature of the metal solution resulted in an increase in the metal uptake per unit weight of the sorbent.
Freundlich isotherm model was found to be applicable for the experimental data of Cu2+ and Zn2+. The results showed that oil shale could be used for the adsorption of the Cu2+ and Zn2+ with higher affinity toward Zn2+ ions. Addition of sodium salt to the metal solution influenced copper removal positively, but inhibited zinc removal.
Received: 3 January 2000 · Accepted: 27 June 2000 相似文献
13.
分别采用不同浓度的NaCl溶液对低塑性黏土进行饱和,然后进行压力板和蒸汽平衡法试验,获得整个吸力范围内的土-水特征曲线（SWCC）。分析不同浓度的孔隙溶液对SWCC的影响规律,结果表明：盐分对基质吸力的影响较小,对总吸力影响较大,这主要是因为盐溶液引起的渗透吸力所致。在蒸汽平衡法试验中,随着含水率的降低,孔隙浓度增大,渗透吸力增大。然而,基质吸力随着含水率的减小迅速增大,使得渗透吸力所占的比例逐渐减小。在非饱和土中,总吸力包括基质吸力和渗透吸力;基质吸力包括毛细部分和吸附部分,当土体中含水率较低时,主要是吸附效应在起作用;渗透吸力与溶液浓度有关。根据试验结果深入分析了吸附水膜和土颗粒之间的相互作用,得出由于溶质的存在对分子间吸附力的影响规律。根据表面化学原理,建立了分子间作用力和吸附水膜厚度之间的关系,以描述处于吸附状态的土-水特征曲线。 相似文献
14.
采用物理模型实验方法对不同潮差驱动下咸水入侵距离进行实验研究,结果表明存在潮差临界值使得咸水入侵距离最短,当潮差小于该临界值,咸水入侵距离随潮差增大呈快速减小趋势,而大于该临界值则呈缓慢增大趋势。基于实验数据对盐淡水混合进行理论分析,揭示了实验现象的产生机制:①潮差增大过程中盐淡水混合由高度分层变为均匀混合,导致驱动咸潮入侵的动力发生了改变;②当盐淡水为弱混合类型,盐淡水高度分层,重力环流输运是盐进入河口的主要方式,潮汐强度增大减小了盐淡水分层,减弱了重力环流的输运作用,因此入侵距离变小;③当盐淡水为强混合类型,盐淡水混合均匀,重力环流输运作用大大减弱,潮汐扩散成为主要的输运方式,潮汐增强使得扩散能力增大,因此潮汐强度越大,咸潮入侵距离越大。 相似文献
15.
Responses of chemically active and naturally fractured shale under time‐dependent mechanical loading and ionic solution exposure 
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下载免费PDF全文 In this paper, the analytical dual‐porosity dual‐permeability poromechanics solution for saturated cylinders is extended to account for electrokinetic effects and material transverse isotropy, which simulate the responses of chemically active naturally fractured shale under time‐dependent mechanical loading and ionic solution exposure. The solution addresses the stresses, fracture pore pressure, matrix pore pressure, fluid fluxes, ion concentration evolution, and displacements due to the applied stress, pore pressure, and solute concentration difference between the sample and the circulation fluid. The presented solution will not only help validate numerical simulations but also assist in calibrating and interpreting laboratory results on dual‐porosity dual‐permeability shale. It is recommended that the analytical solutions of radial and axial displacements be used to match the corresponding laboratory‐recorded data to determine shale dual permeability and chemo‐electrical parameters including membrane coefficient, ions diffusion coefficients, and electro‐osmotic permeability. 相似文献
16.
Analysis of Pore Pressure and Stress Distribution around a Wellbore Drilled in Chemically Active Elastoplastic Formations 总被引：4，自引：1，他引：3
Drilling in low-permeable reactive shale formations with water-based drilling mud presents significant challenges, particularly
in high-pressure and high-temperature environments. In previous studies, several models were proposed to describe the thermodynamic
behaviour of shale. Most shale formations under high pressure are expected to undergo plastic deformation. An innovative algorithm
including work hardening is proposed in the framework of thermo-chemo-poroelasticity to investigate the effect of plasticity
on stresses around the wellbore. For this purpose a finite-element model of coupled thermo-chemo-poro-elastoplasticity is
developed. The governing equations are based on the concept of thermodynamics of irreversible processes in discontinuous systems.
In order to solve the plastic problem, a single-step backward Euler algorithm containing a yield surface-correction scheme
is used to integrate the plastic stress–strain relation. An initial stress method is employed to solve the non-linearity of the plastic equation. In addition, super convergent patch recovery is used
to accurately evaluate the time-dependent stress tensor from nodal displacement. The results of this study reveal that thermal
and chemical osmosis can significantly affect the fluid flow in low-permeable shale formations. When the salinity of drilling
mud is higher than that of pore fluid, fluid is pulled out of the formation by chemical osmotic back flow. Similar results
are observed when the temperature of drilling mud is lower than that of the formation fluid. It is found that linear elastic
approaches to wellbore stability analysis appear to overestimate the tangential stress around the wellbore and produce more
conservative stresses compared to the results of field observation. Therefore, the drilling mud properties obtained from the
elastoplastic wellbore stability in shales provide a safer mud weight window and reduce drilling cost. 相似文献
17.
Most multiple-fractured horizontal wells experience long-term linear flow due to the ultralow permeability of shale gas reservoirs. Considering the existence of natural fractures caused by compression and shear stresses during the process of tectonic movement or the expansion of high-pressure gas, a shale gas reservoir can be more appropriately described by dual-porosity medium. Based on the assumption of slab dual-porosity, this paper uses the trilinear flow model to simulate the transient production behavior of multiple-fractured horizontal wells in shale gas reservoirs, which takes the desorption of adsorbed gas, Knudsen diffusion and gas slippage flow in the shale matrix into consideration. Production decline curves are plotted with the Stehfest numerical inversion algorithm, and sensitivity analysis is done to identify the most influential reservoir and hydraulic fracture parameters. It was found that the density and permeability of the natural fracture network are the most important parameters affecting the production dynamics of multiple-fractured horizontal wells in shale gas reservoirs. The higher the density and permeability of the natural fractures are, the shorter the time is required to exploit the same amount of reserve, which means a faster investment payoff period. The analytical model presented in this paper can provide some insight into the reserve evaluation and production prediction for shale gas reservoirs. 相似文献
18.
Martin Hovland Christine Fichler Hkon Ruesltten Hans Konrad Johnsen 《Journal of Geochemical Exploration》2006,89(1-3):157
Deep-rooted enigmatic piercement structures in sedimentary basins, including ‘mud volcanoes’, ‘shale diapirs’, ‘salt diapirs’, and ‘asphalt volcanoes’, range in size from less than 1 km2, surface area, up to 64 km2, and have often an unknown depth of penetration due to incomplete imaging. We propose that they form a family associated with fluid flow. Our argument is based partly on their inferred location (above deep faults) and on the chemical analysis of emitted products, which includes liquid clays, brines and other substances from salt diapirs, and asphalt and light oils from the asphalt volcanoes. We explain these compositions by chemical alteration caused partly by supercritical water, a phase of water existent at high pressure and temperature, locally and temporarily achieved at depths generally beyond 10 km below surface, i.e., at the sediment–crust boundary. Our hypothesis overcomes some of the problems with interpreting fluid flow products, which are otherwise very difficult to explain. In case this hypothesis can be further verified, the family could perhaps be called ‘hydrothermally associated piercement structures’. 相似文献
19.
为了进行陆相断陷湖盆泥页岩细粒混积岩有利岩相预测,以指导页岩油气有利目标优选,综合运用岩心、薄片、全岩衍射、元素、古生物等资料,系统进行了东营凹陷沙四上亚段泥页岩细粒混积岩沉积环境恢复、岩相精细表征,揭示了沉积环境对岩相及其组合、分布的控制作用.研究表明,东营凹陷沙四上亚段泥页岩细粒混积岩沉积期整体上表现为气候由半湿润向湿润转化,自下而上显示碎屑物源输入量在增加、水体水深加大、盐度降低、还原性减弱的过程;有序复杂多变的沉积环境一定程度上控制了泥页岩细粒混积岩沉积组构复杂性,进而控制了细粒混积岩相的多样性、组合和分布规律性.建立基于“岩石组分、沉积构造、灰质结构和有机质丰度”四端元划分方案,将东营凹陷沙四上亚段泥页岩细粒混积岩划分为20类,实现了复杂细粒混积岩岩相划分;半湿润少物源条件下,浅湖强还原盐水环境主要发育膏盐、含有机质层状膏质泥岩和含有机质层状泥质灰（云）岩相组合,半深湖强还原咸水环境主要发育富有机质纹层状微晶泥质灰岩和富有机质纹层状灰质泥岩频繁互层岩相组合,半深湖强还原半咸水环境主要发育富有机质水平泥晶纹层泥质灰岩和富有机质纹层灰质泥岩频繁互层岩相组合,深湖还原半咸水环境主要发育富有机质层状泥质灰岩夹富有机质层状灰质泥岩相组合;湿润多物源条件下,深湖强还原半咸水环境主要发育富有机质层状泥质灰岩和富有机质层状灰质泥岩频繁互层岩相组合,深湖还原半咸水环境主要发育富有机质层状灰质泥岩夹富有机质层状泥质灰岩相组合. 相似文献
20.
利用土壤板结原理,通过对硫铝酸盐水泥固化土无侧限抗压强度试验和水稳定性试验,探讨钾盐、磷酸盐对其早期强度的影响规律;通过X射线衍射（XRD）对固化土的物相成分进行了分析,探讨钾盐、磷酸盐影响固化土强度的变化内在机制。试验结果表明,钾盐、磷酸盐对固化土强度提高的阈值为0.6%,当盐掺入量低于该阈值时,固化土强度会随着盐掺量的增加而提高,当盐掺入量超过该阈值时,固化土强度会逐渐降低。盐掺入量不超过2%时,掺盐固化土水稳定性与未掺盐固化土差不多,7 d固化土软化系数基本保持在70%以上,但掺入K2SO4的固化土水稳定性较差,软化系数在60%左右。生成高强难溶具有膨胀性的矿物晶体是掺盐固化土早期强度提高的主要原因,但盐掺入量过高,固化土中矿物晶体过多膨胀作用,破坏固化土结构,而使固化土早期强度降低。 相似文献