Implication of Water-Rock Interaction for Enhancing Shale Gas Production

Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation.During these processes,typically,a large amount of working fluid enters the formation,resulting in widespread water-rock interaction.Deeply understanding such effects is required to optimize the production system.In this study,the mechanisms of water-rock interaction and the associated responses of shale fabric are systematically reviewed for working fluids such as neutral fluids,acid fluids,alkali fluids and oxidative fluids.It is shown that shale is generally rich in water-sensitive components such as clay minerals,acidsensitive components(like carbonate minerals),alkali-sensitive components(like quartz),oxidative-sensitive components(like organic matter and pyrite),which easily lead to change of rock fabric and mechanical properties owing to water-rock interaction.According to the results,oxidizing acid fluids and oxidizing fracturing fluids should be used to enhance shale gas recovery.This study also indicates that an aspect playing an important role in increasing cumulative gas production is the optimization of the maximum shut-in time based on the change point of the wellhead pressure drop rate.Another important influential factor to be considered is the control of the wellhead pressure considering the stress sensitivity and creep characteristics of the fracture network.

Dynamic analysis of dam-reservoir-foundation interaction using finite difference technique

Time domain dynamic analysis of inclined dam-reservoir-foundation interaction was conducted using finite difference method （FDM）. The Timoshenko beam theory and the Euler-Bemoulli beam theory were implemented to draw out governing equation of beam. The interactions between the dam and the soil were modeled by using a translational spring and a rotational spring. A Sommerfeld＇s radiation condition at the infinity boundary of the fluid domain was adopted. The effects of the reservoir bottom absorption and surface waves on the dam-reservoir-foundation interaction due to the earthquake were studied. To avoid the instability of solution, a semi-implicit scheme was used for the discretization of the governing equation of dam and an explicit scheme was used for the discretization of the governing equation of fluid. The results show that as the slope of upstream dam increases, the hydrodynamic pressure on the dam is reduced. Moreover, when the Timoshenko beam theory is used, the system response increases.

Fluid interaction mechanism and diagenetic reformation of basement reservoirs in Beier Sag, Hailar Basin, China

Based on analysis of core observation, thin sections, cathodoluminescence, scanning electron microscope(SEM), etc., and geochemical testing of stable carbon and oxygen isotopes composition, element content, fluid inclusions, and formation water, the fluid interaction mechanism and diagenetic reformation of fracture-pore basement reservoirs of epimetamorphic pyroclastic rock in the Beier Sag, Hailar Basin were studied. The results show that:(1) Two suites of reservoirs were developed in the basement, the weathering section and interior section, the interior section has a good reservoir zone reaching the standard of type I reservoir.(2) The secondary pores are formed by dissolution of carbonate minerals, feldspar, and tuff etc.(3) The diagenetic fluids include atmospheric freshwater, deep magmatic hydrothermal fluid, organic acids and hydrocarbon-bearing fluids.(4) The reservoir diagenetic reformation can be divided into four stages: initial consolidation, early supergene weathering-leaching, middle structural fracture-cementation-dissolution, and late organic acid-magmatic hydrothermal superimposed dissolution. Among them, the second and fourth stages are the stages for the formation of weathering crust and interior dissolution pore-cave reservoirs, respectively.

Mineralogical and Geochemical Evidence of Fluid-rock Interaction at the Shallow Crustal Level in Koyna Seismogenic Region, Maharashtra, India: Impact and Implications

The Koyna region of Maharashtra located in the western part of the~65 Myr old Deccan traps province,overlying the Neoarchean cratonic granitoid basement of peninsular India,has been experiencing recurring seismicity since 1962 after the impoundment of the Shivajisagar Reservoir behind the Koyna Dam.

Improvement and Evaluation of the Latest Version of WRF-Lake at a Deep Riverine Reservoir

The WRF-lake vertically one-dimensional(1D)water temperature model,as a submodule of the Weather Research and Forecasting(WRF)system,is being widely used to investigate water-atmosphere interactions.But previous applications revealed that it cannot accurately simulate the water temperature in a deep riverine reservoir during a large flow rate period,and whether it can produce sufficiently accurate heat flux through the water surface of deep riverine reservoirs remains uncertain.In this study,the WRF-lake model was improved for applications in large,deep riverine reservoirs by parametric scheme optimization,and the accuracy of heat flux calculation was evaluated compared with the results of a better physically based model,the Delft3D-Flow,which was previously applied to different kinds of reservoirs successfully.The results show:(1)The latest version of WRF-lake can describe the surface water temperature to some extent but performs poorly in the large flow period.We revised WRF-lake by modifying the vertical thermal diffusivity,and then,the water temperature simulation in the large flow period was improved significantly.(2)The latest version of WRF-lake overestimates the reservoir-atmosphere heat exchange throughout the year,mainly because of underestimating the downward energy transfer in the reservoir,resulting in more heat remaining at the surface and returning to the atmosphere.The modification of vertical thermal diffusivity can improve the surface heat flux calculation significantly.(3)The longitudinal temperature variation and the temperature difference between inflow and outflow,which cannot be considered in the 1D WRF-lake,can also affect the water surface heat flux.

三峡库区碳酸岩岸坡消落带岩体劣化特性

岸坡消落带是库水位升降形成的干湿交替作用区域。与岸坡其他地段相比,岸坡消落带水岩作用强烈,不断改造库岸的形貌特征,影响岸坡的整体或局部稳定性。消落带岩体劣化研究在劣化特征、劣化分类,以及劣化评价方法、指标研究方面存在不足。本文以三峡库区秭归和巴东干(支)流碳酸岩岸坡消落带岩体为研究对象,采取调(勘)查与试验、“比拟法”等综合分析方法,对碳酸岩消落区岩体劣化特征、过程及机制进行了系统研究,得到以下结论。(1)基于岸坡消落区岩体劣化的宏观效应,可划分为4种劣化类型;库水和地下水联动作用影响消落区岩体劣化的范围,沿深度方向呈现逐渐减弱的趋势,根据岩体劣化程度,可划分为3个区。(2)岩体各类结构面劣化最为严重,尤其是裂隙结构面,控制着岩体劣化的主要特征和类型。(3)库水作用方式和水的溶蚀性强弱影响岩体劣化的进展和演化发展模式。(4)根据库水与岸坡地下水联动程度,结合工程应用,提出了碳酸岩岸坡消落带岩体劣化的评价指标和评价方法。研究成果对消落带岩体劣化评价及岸坡稳定性演化评价具有一定的参考意义。

川西磨西断裂湾东地热水化学特征及成因机制

【目的】地热能开发是实现碳达峰、碳中和的重要途径。磨西断裂位于川西鲜水河断裂南段,拥有丰富的地热资源,是未来地热能开发的重点区域。【方法】对四川磨西断裂湾东地热区开展水文地球化学研究,通过水化学相关性分析其水-岩作用过程,利用地热温标、硅-焓混合模型等方法计算其热储温度、冷热水混合比例,采用氢氧同位素探明补给来源和补给高程。【结果和结论】结果显示:磨西断裂地热水的水化学类型包括HCO_(3)·Cl-Na型和HCO_(3)·SO_(4)-Ca·Mg型。地热水的水化学组分主要受水-岩作用(泥盆系大理岩方解石矿物溶解)影响,其中HCO_(3)·Cl-Na型地热水在磨西断裂深部受岩浆水混合和CO_(2)脱气作用影响。HCO_(3)·Cl-Na型地热水热储温度较高(159.16~228.57℃),沿磨西断裂循环深度较大;HCO_(3)·SO_(4)-Ca·Mg型地热水的热储温度较低(111.02~138.04℃),沿次级构造草科断裂运移,循环深度较小。地热水的补给来源均为大气降水和深部岩浆水,补给区为湾东地热区西部贡嘎山,补给高程在2 382~2 981 m。本次研究探明了湾东地热区存在2种不同成因模式,其水化学特征和热储温度差异显著,可为该区地热能开发提供更具针对性的理论依据。

高坝大库滑坡涌浪对水工建筑物作用力研究综述

库坝区滑坡体入水激起的涌浪灾害链对水工建筑物构成安全威胁.本文对高坝大库滑坡涌浪对水工建筑物作用力相关研究成果和发展趋势进行综述,概述了国内外典型滑坡涌浪实例及其危害,基于规范推荐公式、物理模型试验和数值模拟方法对库区滑坡涌浪对大坝坝体冲击压力相关研究成果进行总结归纳,提出应关注涌浪二次冲击阶段对水工结构的影响、开展坝前涌浪回落对坝面构筑物结构产生拖曳力的相关研究.总结了涌浪对通航建筑物作用力的相关研究,分析表明,现有关于涌浪对通航建筑物作用力的研究并不完全适用于库区滑坡涌浪对高坝水工结构作用,需开展专题研究.在现状分析的基础上,对高坝大库滑坡涌·浪对水工建筑结构作用的进一步研究提出了建议与展望.

长江上游高坝大库垂向微生物结构及其网络互作

长江上游一系列高坝大库导致水体光、温、氧等呈现特有的垂向分层特征,导致垂向微食物网结构发生变化。本文选取长江上游典型高坝大库溪洛渡、向家坝、三峡大坝坝前垂向生境为研究对象,于2019年从坝前垂向采集了5个不同深度水层的水样,开展了坝前垂向生境特性和微生物群落结构的调查研究。研究发现,7月溪洛渡坝前垂向从90到140m,溶解氧浓度先降低后增加。溪洛渡水库5月在距水体表层40~60m处发生温跃,7月在距水体表层80~120m处发生温跃。向家坝水库5月在水层底部附近出现温跃。不同深度水层物种组成种类和丰度无显著差异,但香农多样性存在差异,并且从表层到底层,香农指数先降低后增加。蓝藻丰度在不同水深差异显著。共现网络分析表明,不同深度水层微生物间的相互作用以正相互作用为主;第二层水层水样微生物群落具有最高的模块化程度,比其他水深处的共发生网络具有更高的复杂度;藻类在微食物网中具有重要作用:藻类与细菌、藻类与原生动物、细菌与原生动物的互作是水生生态系统微食物网之间的主要互作类型,占物种间总互作的81.50%。研究结果表明,坝前垂向不同深度水层微食物网结构和物种间的相互作用在温度、溶解氧浓度等环境因子的作用下存在差异。

柴西地区中新世致密油藏源储特征及其组合特征

致密油源储特征及其组合因素研究对发展非常规油气地质理论具有重要意义。选取柴达木盆地西部地区中新世致密油藏为主要研究对象,通过岩心描述、扫描电镜观察及高压压汞实验等手段,结合柴西地区的地质、地球物理等资料,重点探究了其烃源岩与储层特征,并分析了源储关系以及致密油藏中源储组合特征。结果表明:1)上干柴沟组烃源岩以泥岩和泥灰岩为主,有机质丰度较高,以较差-好烃源岩为主,有机质类型以Ⅱ_(1)型为主,且处于低熟-成熟阶段。2)上干柴沟组致密储层以细砂-粉砂岩为主,物性较差,低孔低渗特点显著,储集空间类型为残余粒间孔隙-微裂隙,属于细微孔喉型储层。3)柴西地区中新世致密油存在低熟原油和成熟原油2类油源,分别来源于上干柴沟组和下干柴沟组烃源岩。上干柴沟组致密油藏源储关系主要为源储互交组合和源储侧交组合,源储互交组合最为发育。

广东省粤中断裂型碳酸盐岩地热水的水文地球化学研究——以马星-隔陂地热系统为例

粤中地区地热资源丰富,但人们对断裂型碳酸盐岩地热水地球化学过程的认识存在一定争议。本文以马星-隔陂地热系统为例,采用Piper图、离子比例系数、Gibbs图和主成分方法(PCA法)针对其断裂型碳酸盐岩地热水水化学特征进行综合分析。

R290高背压旋转压缩机极端环境下储液器热分析

以制冷剂R290为研究工质,主要分析了极端环境下旋转压缩机气液分离器(储液器)中产生的无效过热情况及其对性能的影响程度。首先利用计算流体动力学(CFD)技术建立了储液器详细的流固耦合仿真模型用于研究极端环境储液器的吸气加热情况;其次分析了极端环境下储液器内的吸气加热对压缩机性能的影响。结果表明,极端制热条件下储液器的吸气加热温升比极端制冷大;减小储液器内的吸气温升对压缩机性能提升明显。研究工作将为极端环境下储液器传热优化及其压缩机性能提升提供一定参考。

Understanding of mineral change mechanisms in coal mine groundwater reservoir and their influences on effluent water quality:a experimental study

This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.

A preliminary snapshot of the trophic model and ecosystem attributes of Kaptai reservoir ecosystem, Bangladesh

A mass-balanced Ecopath model presents a quantitative description of the trophic structure,fl ow of energy and trophic interaction among ecological groups of an ecosystem.The Ecopath with Ecosim(EwE)modeling program(Version 6.5)was used to develop a preliminary trophic model for a tropical freshwater reservoir.The total fi sh biomass was 6.245 t/km 2 and the highest trophic level of the reservoir was 3.362(for snakehead).The ecosystem is phytoplankton based because primary producers originated 68%and detritus originated 32%of the total fl ow from lower trophic level.The gross effi ciency of the fi shery was 0.004,suggesting the ineffi ciency of the system.The positive eff ect of phytoplankton and detritus on most of the other groups were evident from mixed trophic analysis while moderately higher ecotrophic effi ciency(EE)of phytoplankton shows the ecosystem’s potential bottom-up control.The competition for the same resources among diff erent groups was also obvious.The ratio of primary production/respiration(1.969)suggests that the ecosystem is at the developing stage and utmost contemplation should be given to concerned human activities.The low value of relative ascendancy(30.13)and overhead(69.87)reveals the stability of the ecosystem and some degrees of maturity.It also predicts the presence of signifi cant strength in reserve of the system to withstand or overcome any perturbation.However,ecologically sustainable resource management plans should be implemented to ensure the sustainability of this reservoir resources.

Application of Vegetation Geosynthetic Technique to Slope Stability in the Three Gorges Reservoir

The vegetation geosynthetic reinforced slope is one of the new composite structures in civil engineering. It has a series of characteristics, such as low cost, convenient construction, optimal land utilization and flexible structure, and it has been widely used in hydraulic engineering, road, railway and harbor construction. The Three Gorges reservoir bank protection system is a challenging work. As the background, the interaction mechanism of soil and reinforced material has been studied. The test engineering is simulated by the numerical methods. The failure mechanism of the reinforced slope in the process is studied through analyzing the variation of the displacement, stress, plastic failure fields and factor of safety in the changing process of the water level. The reasonable evaluation of the protecting effect and bank slope stability is carried out. The research results could be used in the protective design and construction in the high slope in the Three Gorges reservoir region, and it also could provide reference to other protective engineerings in the littoral area.

Frequencies of Lock Gate Structure Coupled with Reservoir Fluid

This study determines the natural frequencies of the lock gate structure,considering the coupled effect of reservoir fluid on one side using the finite element method(FEM).The gate is assumed to be a uniformly thick plate,and its material is isotropic,homogeneous,and elastic.The reservoir fluid is assumed to be inviscid and incompressible in an irrotational flow field.The length of the reservoir domain is truncated using the far boundary condition by adopting the Fourier series expansion theory.Two different assumptions on the free surface,i.e.,undisturbed and linearized,are considered in the fluid domain analysis.The computer code is written based on the developed finite element formulations.The natural frequencies of the lock gate are computed when interacting with and without reservoir fluid.Several numerical problems are studied considering the effects of boundary conditions,aspect ratios,and varying dimensions of the gate and the fluid domain.The frequencies of gate reduce significantly due to the presence of fluid.The frequencies increase when the fluid extends to either side of the gate.The frequencies reduce when the depth of the fluid domain above the top edge of the gate increases.The frequencies drop considerably when the free surface condition is taken into account.The results of frequencies of lock gate structure may be useful to the designer if it is experienced in natural catastrophes.

Reservoir Characterization of the Early Jurassic Butmah Formation Using Well Log Data in Selected Wells from Iraqi Kurdistan Region

The reservoir characterization of Butmah Formation (Early Jurassic) was studied in two wells: (AT-1) and (SH-1B) from Atrush and Shaikhan Oilfields respectively, in Iraqi Kurdistan Region. Well logs including;sonic, density, neutron, gamma ray, and resistivity, were employed to investigate the formation. The petrophysical properties, such as lithology, shale volume, porosity, water saturation, hydrocarbon saturation, and bulk water volume, were estimated using Interactive Petrophysics Software (IP). Water saturation, bulk volume of water, residual hydrocarbon, and movable hydrocarbon were plotted as Computer Processed Interpretation (CPI) for Butmah Formation in the studied wells. In order to check reliability of log data, lithology of the formation was detected using neutron-density cross plot and M-N cross plot. The results of log interpretation display that Butmah Formation is composed of dolomite, limestone with anhydrite and shale in the studied wells. The calculated shale volume shows low clay content. Therefore, Butmah Formation is considered as a clean formation in both wells. Porosity was estimated using porosity logs (sonic, density, and neutron) and had the average total porosity of (7% - 8%) in the two wells. Based on the determined petrophysical properties, particularly porosity and hydrocarbon saturation, it can be concluded that Butmah Formation seems potentially good in reserving oil.

Evolution of nC_(16)H_(34)-water-mineral systems in thermal capsules and geological implications for deeply-buried hydrocarbon reservoirs

Organic-inorganic interactions between hydrocarbons and most minerals in deeply buried reservoirs remain unclear.In this study,gold capsules and fused silica capillary capsules(FSCCs)with different com-binations of nC_(16)H_(34),water(distilled water,CaCl_(2) water)and minerals(quartz,feldspar,calcite,kaolinite,smectite,and illite)were heated at 340℃ for 3-10 d,to investigate the evolution and reaction pathways of the organic-inorganic interactions in different hot systems.After heating,minerals exhibited little alteration in the anhydrous systems.Mineral alterations,how-ever,occurred obviously in the hydrous systems.Different inorganic components affected nC_(16)H_(34) degra-dation differently.Overall,water promoted the free-radical thermal-cracking reaction and step oxidation reaction but suppressed the free-radical cross-linking reaction.The impact of CaCl_(2) water on the nC_(16)H_(34) degradation was weaker than the distilled water as high Ca^(2+)concentration suppressed the formation of free radicals.The presence of different waters also affects the impact of different minerals on nC_(16)H_(34) degradation,via its impact on mineral alterations.In the anhydrous nC_(16)H_(34)-mineral systems,calcite and clays catalyzed generation of low-molecular-weight(LMW)alkanes,particularly the clays.Quartz,feldspar,and calcite catalyzed generation of high-molecular-weight(HMW)alkanes and PAHs,whereas clays catalyzed the generation of LMW alkanes and mono-bicyclic aromatic hydrocarbons(M-BAHs).In the hydrous nC_(16)H_(34)-distilled water-mineral systems,all minerals but quartz promoted nC_(16)H_(34) degra-dation to generate more LMW alkanes,less HMW alkanes and PAHs.In the nC_(16)H_(34)-CaCl_(2) water-mineral systems,the promotion impact of minerals was weaker than that in the systems with distilled water.This study demonstrated the generation of different hydrocarbons with different fluorescence colors in the different nC_(16)H_(34)-water-mineral systems after heating for the same time,implying that fluorescence colors need to be interpreted carefully in investigation of hydrocarbon charging histories and oil origins in deeply buried reservoirs.Besides,the organic-inorganic interactions in different nC_(16)H_(34)-water-mineral systems proceeded in different pathways at different rates,which likely led to preservation of liquid hydrocarbons at different depth(temperature).Thus,quantitative investigations of the reaction kinetics in different hydrocarbon-water-rock systems are required to improve the prediction of hydrocar-bon evolution in deeply buried hydrocarbon reservoirs.

库岸边坡消落带水-岩作用研究进展与展望

消落带岩体的损伤劣化直接影响库岸边坡的长期变形稳定.近年来,相关模拟库岸边坡消落带的水-岩作用的试验设备和测试技术逐步发展,消落带水-岩作用劣化效应及机理研究逐步完善,相关研究进展主要体现在如下4个方面:库岸边坡消落带水-岩作用试验方法从干湿循环逐步发展到考虑库水压力变化以及应力和水-岩耦合作用,但相关模拟复杂应力条件和库水环境耦合作用的专用仪器设备和方法亟待进一步研究完善;水-岩作用下各类岩石的劣化规律和微细观结构损伤演化特征得到系统研究,并建立了多种损伤劣化模型,但复杂赋存条件下库岸边坡消落带岩体损伤劣化与地层岩性、坡体结构的相关关系,以及消落带岩体的损伤劣化机理及模型亟待完善;在消落带岩体劣化现场测试方面,声波、回弹、探地雷达和钻孔成像技术逐渐得到应用,但相关适用于大范围、长周期的消落带岩体劣化现场测试及分析技术亟待完善;消落带岩体劣化已经逐渐成为影响岸坡长期变形稳定的因素之一,但消落带岩体损伤劣化诱发岸坡局部或者整体变形失稳的临界条件、变形破坏模式分析还不够系统.

采空区破碎煤岩体溶蚀作用及净水机理实验研究

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