Water quality assessment of benthic diatom communities for water quality in the subalpine karstic lakes of Jiuzhaigou,a world heritage site in China

Jiuzhaigou, characterized by its magnificent waterscapes and subalpine karstic features, is both a World Heritage Site and a World Biosphere Reserve in southwestern China. In recent years, this unique ecosystem has shown signs of stress due to increasing tourism activities within the reserve. The various routine methods, which monitor physical and chemical properties, do not fully reflect water quality in the subalpine and alpine lakes, while the indicators using aquatic organisms to evaluate the water quality or status of the subalpine lakes are poorly reported. Thus, in this study, benthic diatoms from multiple habitats in Jiuzhaigou were sampled and assessed for water quality monitoring. Canonical Correspondence Analysis （CCA） showed that the canonical coefficients for elevation, water temperature and total nitrogen on the first Canonical Corresnondence Analysis axis were -0.84. 0.78 and -0.53, respectively, environmental variables associated with the distribution patterns of benthic diatoms. The dominance of diatom taxa indicative of nutrient enrichment indicates a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists. It was observed that the effect of the type of substratum on diatom community composition is not significant in subalpine lakes. The most dominant species in Jiuzhaigou lakes are the genera Achnanthes, Fragilaria, CymbeUa, Cocconeis, Diatoma and Denticula. In combination with dominant and sensitive species in the benthic diatom communities, CCA and CA methods can be used to evaluate the impact of human activities on subalpine karstic lakes. The dominance of diatom taxa is indicative of nutrient enrichment and the results of CCA and CA indicate a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists.

The mechanism and criterion of tectonic zone around karstic collapse column reactivation-induced water-conducting

In order to study the mechanism of tectonic zone around karstic collapse col-umn reacts to leak water and prevent water invasion in mine. According to the character of the surrounding cracks- penetrated water KCC, The fracture mechanics theory can be used to study the propagation and perforation process of cracks and hitches around the KCC. The criterion of crack start rupture and the length of secondary crack and criterion of crack propagation have been attained. The influencing factors of KCC reacts to water con-duction were analyzed.

Blasting practices in a quarry with karstic cavities

The blasting practices in a limestone quarry with karstic cavities have beenpresented. The existence of karstic cavities in the quarry has reduced blasting efficiencysignificantly. In order to improve blasting efficiency different blasting strategies (loading holeswith ANFO in plastic bag, recording cavity location along the holes and charging the holes accordingto this information, and modifying blasting pattern according to karstic cavities) had beenimplemented and the results were evaluated on per ton cost basis. It was concluded that efficientblasting in such aquarries requires determining the size and shape of karstic cavities and based onthis information, to modify the blast pattern and charge the holes. The suggested method is torecord the cavity along the drill hole and to generate 3D model of cavities. By doing this, theproduction cost in the limestone quarry has decreased from 0.407 dollars/t to 0.354 dollars/t.

Studying Subsidence Coefficient of Mirages and Dynamic Storage Volume of Karstic Springs of Khorram Abad, West of Iran

The studied subject is about subsidence coefficient of mirages and dynamic storage volume of Karstic springs in Khorram Abad in West of Iran. Subsidence coefficient indicates ability of groundwater discharge and hydrologic properties of the environment;meaning effective porosity and transfer coefficient of springs. In general, in developed Karstic zones, each direct line of subsidence curve indicates a discharge regime. Obtained results from the study show that subsidence branch of Golestan, Motahari, Niloofar (changaei), Navekech, Dore Robat mirages have subsidence coefficient with mild slope and low value, which demonstrate passage of water through a seams system at the karst springs. Q and whirlpool stone mirages have two subsidence coefficients, which indicate passage of water through two seam systems in Karstic environment of springs. According to obtained results, process of changes in subsidence branch in these mirages has had at the first a mild slope and low discharge coefficient and in continue, its discharge would be declined with sharper slope and high discharge coefficient. In order to estimate dynamic storage volume of springs, MAILET general equation is applied, which is suitable for subsidence branch of hydrographs of centralized springs discharge. Following, dynamic storage volume of studied springs is analyzed and obtained results are presented in this study respectively.

Use of GIS to Estimate Recharge and Identification of Potential Groundwater Recharge Zones in the Karstic Aquifers,West of Iran

Estimating and studying groundwater recharge is necessary and important for the management of water resources.The main aim of this work is to estimate the value of the annual recharge in some parts of the Kermanshah and Kurdistan province located in the west of Iran.There are many ap­proaches available for estimation of the recharge,but RS(remote sensing)and GIS(geographic information system)have provided and combined a lot of effective spatial and temporal data of large areas within a short time.For this purpose,nine information layers including the slope,aspect of slope,lithology,lineament density,drainage density,precipitation,vege­tation density,soil cover,and karst features were prepared and imported to the ArcMap software.After preparing the information layers,they have to weigh based on their effects on the value of the recharge.In order to be weighted the different parameters,methods of judgment expert,reciprocal influences of parameters,and AHP were used.Using GIS,the results ob­tained from the final map indicated the average value for the recharge based on the average calculated coefficient of recharge.The annual recharge coef­ficient in the study area was estimated to be between 30%and 80%.

Characteristics of dolomite karstic reservoir in the Sinian Dengying Formation,Sichuan Basin

The Sinian dolomite reservoir in Dengying Formation was developed extensively in the Sichuan Basin,and typically was the facies-controlled dolomite karstic reservoir.The development of this kind of the reservoir was related with the special deposits,diagenetic environment as well as the multi-phase and multi-type dissolution and fracturing actions.The arid-hot/dry paleo-climate was favourable to develop the large-scale microbial reef-shoal bodies and moundeshoal bodies,which was characterized by the organic framework and the sea floor hardening,thus forming primary matrix pore-type reservoir.In the background of the arid-hot/dry paleo-climate,the water-rock interaction was weak,the mineral stabilization process was slowly,and the vadose pisoliths,aragonite and high-magnesium calcite were well preserved,therefore,this diagenetic environment especially was beneficial for pore preservation.Moreover,the syngenetic and penecontemporaneous dissolution,especially three phases of weathered crust karstification due to three episodes of the Tongwan movement,led to further dissolution of spaces and form numerous non-fabric selective dissolution fractures and dissolution caves along faults and fractures.Multi-phase fractures,especially the late Yanshanian-Himalayan tectonic fractures,resulted in connection among pores,vugs and dissolution caves,and improved quality of the reservoir tremendously.

Characteristics and formation of sinian(Ediacaran)carbonate karstic reservoirs in Dengying Formation in Sichuan Basin,China

The Gaoshiti-Moxi Gas Field has been discovered recently in the central part of Sichuan Basin,which might be the biggest gas field in China.In this gas field,a large amount of gas is from Neoproterozoic Sinian(Ediacaran)karstic carbonate rocks.The gas was originated from cracking of oil,and the oil source rocks are the Sinian and Cambrian strata.In this study,the characteristics of these carbonate reservoir rocks have been studied based on subsurface data and outcrop observation.The carbonate rocks are at the Sinian Dengying Formation,and the reservoir properties are controlled by sedimentary facies and diagenesis.The Dengying Formation is composed of algal mounds and grainstone build-ups,which were developed in a restricted platform setting from glacial period to interglacial period.Due to tectonic movement and eustatic cycle in Sichuan Basin during Neoproterozoic Era,five sedimentary cycles of transgression and regression have been developed in the Dengying Formation.According to the sedimentary facies and carbon-oxygen isotope variation,five sedimentary cycles have been recognized.Due to the penecontemporaneous dolomitization,together with hypergene karstification and late burial dissolution,the reservoir properties of the carbonates rocks have been improved greatly.

基于用高斯分布生成管道的岩溶地下水流数值模拟

为更精确地模拟岩溶区地下水运动,以贵州省黔西南普安县某岩溶水文地质单元为研究区,用基于有限单元法的FEFLOW软件建立研究区岩溶管道等效多孔介质耦合地下水流数值模拟模型。模拟中,在地质条件控制下应用高斯随机分布生成地下暗河的管道,用非稳定三维地下水运动的偏微分方程描述等效多孔介质水流运动,用Manning-Strickler方程描述管道水流运动,将导水断层处理为强渗透条块,将落水洞汇水范围的降水入渗系数设置为1,将泉水处理为定水头的抽水井。流场模拟结果显示,25个观测点计算水位与实测水位关系的决定系数可达到0.9985,纳西效率系数达0.9982,极接近于1;表明基于这些处理建立的地下水模拟模型反映了岩溶地下水运动特征,具有较强的仿真能力,可用于提高岩溶区地下水资源评价精度。

广东龙门地区岩溶热储特征及地热系统成因

中国广东省地热资源丰富,岩溶热储分布广泛,极具勘探开发潜力.研究岩溶型地热系统成因对广东省乃至中国南方岩溶型地热资源的勘探开发利用具指导意义.采用地质调查、钻井测量和水文地球化学等方法,多视角系统性地研究广东龙门地区岩溶型地热田特征及其形成机理.结果表明,龙门地区岩溶热储层主要赋存在龙门和永汉等断拗陷盆地的下石炭统石磴子组(C1sh)和上泥盆统天子岭组(D3t)碳酸盐岩层中,以岩溶溶洞裂隙热水为主,埋藏浅,主热储层埋深0~300 m.地热流体化学类型以HCO_(3)-Ca·Na型和HCO_(3)-Ca型为主,其次为SO_(4)-Ca·Na型和HCO_(3)·SO_(4)-Na型,溶解性总固体85~1 284 mg/L,实测水温为25.4~79.9℃.热水氢氧同位素组成表明,大气降水为主要的补给来源,补给高程为57~584 m;13C同位素分析表明,地热水中碳的来源具有多重性,未受到碳酸盐变质作用的影响,根据14C方法测定地热水的年龄介于1.62~14.29 ka.二氧化硅(玉髓)温标热储温度为72~120℃,循环深度为1 814~3 504m.热储受断裂带和碳酸盐岩层位控制,总体呈带状兼层状,热源为相对较高的大地热流和花岗岩体的放射性生热.以上认识揭示了广东龙门地区岩溶热储特征及地热系统成因机理.

耦合CO_(2)脱气的岩溶地热水结垢趋势定量分析

岩溶地热系统是最具开发潜力的水热型地热系统之一,在水热型地热资源利用中,地热水结垢(尤其是井下结垢)是目前面临的最普遍、最重要的问题之一,制约着地热水资源可持续利用。针对岩溶地热水结垢趋势分析方法存在的不足,在重点考虑CO_(2)脱气这一重要过程对结垢趋势影响的基础上,利用化学热力学模拟技术构建了一种耦合CO_(2)脱气过程的结垢趋势定量分析的改进方法,并将其应用于南京汤山岩溶地热区。结果表明汤山地区地热水不具有发生SiO 2结垢的趋势;在井口有发生碳酸盐结垢趋势,主要成分为CaCO_(3);井筒中下部有发生不同程度的硫酸盐结垢趋势,主要成分为CaSO_(4),SrSO_(4),BaSO_(4)。本研究在改进结垢趋势分析方法不足的同时,为防垢除垢工作提供了理论基础和方法指导,可有力促进地热水资源的可持续利用。

岩溶热储合理采灌井距的热突破约束——以菏泽地热田为例

与煤炭、石油、天然气等传统化石能源相比,地热能具有资源储量大、分布广、可再生、开采条件好等优点。菏泽潜凸起地热田是山东省主要大型碳酸盐岩岩溶热储地热田之一,地热资源储量丰富。为保证地热资源可持续开发利用,本文基于郓城县武安府前小区、文昌苑社区岩溶热储地热采灌井全井段地温场长期动态监测,阐述了地温场变化规律及演化趋势,建立水-热耦合采灌对井数值模型,计算回灌工程合理采灌井距、合理采灌量,防止开采井运行期内发生热突破。结果表明,随着回灌年限的延长,回灌井周围热储温度逐年降低,回灌冷水影响范围逐渐扩大。将开采井热储温度降低1℃视为热突破,利用数值模型模拟预测,回灌低温冷水影响范围随采灌工程运行逐渐扩展并到达开采井附近。随着采灌量的增加或采灌井间距的减小,开采井周边的低温范围逐渐增大,产生热突破的时间逐渐缩短。热突破时间t与回灌量Q呈幂函数减小、与采灌井间距R呈指数函数增长。采灌量50 m^(3)/h,采灌井距大于350 m可保证对井系统运行100年不发生热突破;采灌量70 m^(3)/h、90 m^(3)/h、120 m^(3)/h、150 m^(3)/h、180 m^(3)/h时,100年不发生热突破的合理采灌井距分别为400 m、425 m、475 m、500 m、550 m。该结论为采灌井合理布局、地热资源可持续循环开发提供科学依据。

河南省渑池铝土矿田地质特征及成矿规律

渑池铝土矿田是豫西地区重要的铝土矿聚集区,已发现大型铝土矿床10余处,但综合研究程度低、成矿规律认识不清晰,未开展深部成矿预测。文章对渑池铝土矿田的地质背景、矿体、矿石矿物和地球化学特征等进行了详细地研究,重点介绍了侯岭铝土矿和礼庄寨铝土矿的矿体特征、矿物组成、结构构造和主要化学成分,分析了含铝岩系化学组分的变化规律、物源风化强度、风化沉积环境、成矿物质来源和成矿作用规律等,结合岩相古地理及构造演化等研究成果,认为渑池铝土矿是长期风化残余堆积的产物,成矿物质具有多源性,经历了多期次、周期性的沉积成矿,淋滤作用使铝土矿品位大幅提高。渑池铝土矿具有受古岩溶地貌控制的多沉积中心成矿特征,铝土矿形成时,渑池地区呈缓倾的准平原喀斯特地貌,铝土矿大面积富集成矿,经成岩后的多期构造改造,形成了以向斜为主的构造格局,使向斜核部和南翼的含矿地层深埋,预测向斜的中深部仍赋存大规模的优质铝土矿。

岩溶热储古岩溶发育机制与地热水富集模式

明晰岩溶储层古岩溶发育机制、形成演化及发育特征对揭示地热资源赋存特征与富集规律具有重要意义。以济南北地热田为例,在厘清奥陶纪马家沟群地层层序及沉积相特征基础上,通过地表岩溶、钻孔揭露地下岩溶发育特征及富水性分布规律的分析,研究岩溶热储古岩溶作用类型及发育机制,重塑济南北地热田岩溶发育与演化过程并阐明强岩溶发育与地热水富集模式。结果表明:同生岩溶、古风化壳岩溶、埋藏岩溶等三级岩溶发育过程驱动控制区域岩溶的分布层位及发育程度,构造岩溶驱动控制裂隙岩溶发育强度,重力势能驱动控制地热水循环深度和岩溶发育深度;奥陶系顶板以下320 m深度范围内,层间岩溶与构造岩溶复合处、层间岩溶与侵入岩体接触带是强岩溶发育带和地热水富集带。

塔中与塔河地区奥陶系岩溶储层形成条件的差异

对比研究表明,塔中、塔河地区奥陶系岩溶型储层存在显著差异,塔中奥陶系白云岩储层以小型岩溶孔洞为特征,而灰岩储层以发育局限的岩溶洞穴型储层为特征;塔河地区岩溶洞穴型储层以大面积、多层系、叠置连片的分布为特征。造成塔中、塔河地区奥陶系岩溶型储层差异的主要原因是构造演化、古地理岩相和可溶岩岩石类型之间的差异。加里东中期塔中地区冲断褶皱强烈发育,可溶的白云岩或灰岩地层呈窄条带状分散出露,岩溶斜坡发育局限;塔河地区构造活动微弱。海西早期塔河地区整体抬升幅度大,地层强烈剥蚀夷平,可溶的灰岩地层大面积平缓出露,岩溶斜坡发育,大气水沿先前的裂隙系统流动并呈管状流溶蚀改造裂隙,形成大型洞穴系统,多套洞穴储层大面积多层系叠置连片分布;塔中地区构造活动却相对平缓。因此,塔中地区以加里东期岩溶为主。

鄂尔多斯盆地南部加里东期岩溶古地貌与天然气成藏条件分析

认识鄂尔多斯盆地南部地区岩溶古地貌和成藏条件是加快该地区勘探步伐面临的重要问题。鄂尔多斯盆地南部加里东期风化壳储集层的分布主要受岩溶古地貌、风化壳层位及沉积相控制。马五段为云坪相带,溶蚀孔洞较为发育;平凉组为深水斜坡相带,多形成断裂、裂缝及洞穴储集空间。中央古隆起西侧古地貌为岩溶斜坡,地表岩溶作用较弱,但断裂发育,洞穴系统较发育;中央古隆起南侧古地貌为岩溶台地,断裂、洞穴系统和风化裂隙相对较为发育;中央古隆起区古地貌为岩溶台地,地层较老,岩性致密,风化壳顶部垂直裂隙带发育,岩溶孔洞不发育;中央古隆起东侧古地貌多属于岩溶阶地或鞍地,风化壳多位于云坪及含膏云坪相带,溶蚀孔洞较为发育。岩溶古地貌天然气成藏主控因素主要为生烃中心、岩溶古地貌、风化壳的层位和沉积相带,有利区带主要在耀县、旬邑、淳化平凉组生烃中心和中央古隆起东侧马五段有利沉积相带。