Genesis Types and Diagenesis Compaction Mechanisms of Sandstone Rreservoirs in Dynamic Environments in Oil/Gas Basins in China

The diversity of sandstone diagenesis mechanisms caused by the complex geological conditions of oil/gas basins in China could hardly be reasonably explained by the traditional concept of burial diagenesis. Three genesis types of thermal diagenesis, tectonic diagenesis and fluid diagenesis are presented on the basis of the dynamic environment of the oil/gas basins and.the controlling factors and mechanisms of sandstone diagenesis. Thermal diagenesis of sandstone reservoirs is related not only to the effect of formation temperature on diagenesis, but also to the significant changes in diagenesis caused by geothermal gradients. The concept of thermal compaction is presented. Thermal compaction becomes weaker with increasing depth and becomes stronger at a higher geothermal gradient. At the same formation temperature, the sandstone porosity in the region with a lower geothermal gradient is e^0.077＋0.0042T times higher than that in the region with a higher geothermal gradient. Both sudden and gradual changes are observed in diagenetic evolution caused by structural deformation. Average sandstone compaction increased by 0.1051% for every 1.0MPa increase of lateral tectonic compressional stress, while late tectonic napping helped to preserve a higher porosity of underlying sandstone reservoir. Fluid diagenesis is a general phenomenon. The compaction caused by fluid properties is significant. The coarser the grain size, the stronger the fluid effect on compaction. The greater the burial depth, the weaker the fluid effect on compaction for the specific reservoir lithology and the greater the difference in the fluid effects on compaction between different grain sizes.

The Middle Miocene lobe-shaped and band-shaped submarine fans in the Lingshui Sag,Qiongdongnan Basin:source-to-sink system,genesis and implication

Deepwater oil and gas exploration is the key to sustainable breakthroughs in petroleum exploration worldwide.The Central Canyon gas field has confirmed the Lingshui Sag is a hydrocarbon-generating sag,and the deepwater reservoirs in the Lingshui Sag still have more fabulous oil and gas exploration potential.Based on drilling data and three-dimensional(3D)seismic data,this paper uses seismic facies analysis,seismic attribute analysis,and coherence slice analysis to identify the types of submarine fans(lobe-shaped and band-shaped submarine fans)that developed in the Lingshui Sag during the Middle Miocene,clarify the source-to-sink system of the submarine fans and discuss the genesis mechanism of the submarine fans.The results show that:(1)the deepwater source-to-sink system of the Lingshui Sag in the Middle Miocene mainly consisted of a“delta(sediment supply)-submarine canyon(sediment transport channel)-submarine fan(deepwater sediment sink)”association;(2)the main factor controlling the formation of the submarine fans developed in the Lingshui Sag was on the relative sea level decline;and(3)the bottom current reworked the lobe-shaped submarine fan that developed in the northern Lingshui Sag and formed the band-shaped submarine fan with a greater sand thickness.This paper aims to provide practical geological knowledge for subsequent petroleum exploration and development in the deepwater area of the Qiongdongnan Basin through a detailed analysis of the Middle Miocene submarine fan sedimentary system developed in the Lingshui Sag.

Mechanical genesis of Henan(China) Yima thrust nappe structure

Considering the serious coal and rock dynamic disasters around the main slip plane called F16 in the coal mining area) of Henan Yima(China) thrust nappe structure,the mechanical genesis of the Yima thrust nappe structure was studied comprehensively using geomechanics,fault mechanics,elastic mechanics,and Coulomb's law of friction.First,using the centrifugal inertia force of Earth's rotation as a source,a mechanical model of N-S compression superimposed with W-E reverse torsion was established to explain the formation of the early Yima coal basin and Jurassic Yima Group coal measures.Second,an equation for the ultimate stress in the forming stage of F16 was derived using the plastic slip-line field theory and the parabolic Mohr failure criterion.Moreover,the distribution of ultimate stress and the geometric characteristics of the fault profile were obtained using the field model parameters.Finally,the stress field of F16 and the mechanical genesis of the large-scale reverse thrust sheet were discussed based on elastic mechanics theory and Coulomb's law of friction.The results show that the tectonic framework of the early Yima coal basin and the formation pattern of Jurassic Yima Group coal measures given by the model are consistent with the in-situ explorations.The geometric characteristics of the fault profile obtained by numerical calculation can better reflect the shape of F16 in its forming stage,and the mechanical genesis of the large-scale reverse thrust sheet also concurred with the field situations.Thus,this work can provide a foundation for further studies on the genesis of the thrust nappe structure,the mechanism of rock bursts induced by F16,and the characteristics of the residual stress field in the Yima mining area.

Mechanism of carbonate cementation and its influence on reservoir in Pinghu Formation of Xihu Sag

Carbonate cements are the most abundant authigenic mineral and impact on physical properties greatly in sandstone reservoir.In this paper,Pinghu Formation of Xihu Sag was taken as a target.Characteristics,distribution and formation of carbonate cements were investigated via optical microscopy,cathodoluminescence(CL),electron probe and in-situ carbon-oxygen isotope.The results showed that carbonate cements varied in types and shapes.Calcite/dolomite mainly present as poikilotopic cements,while ferrocalcite/ferrodolomite/ankerite generally present as pore-filling cements.Carbon isotope(δ^(13)C)values of carbonate cements were ranging from–7.77‰to–2.67‰,with an average of–4.52‰,while oxygen isotope(δ^(18)O)values were ranging from–18.94‰to–12.04‰,with an average of–14.86‰.Theδ^(13)C/δ^(18)O indicated that the paleo-fluid of carbonate cement was mainly freshwater.Organic carbon mainly came from organic matter within mature source rocks,and inorganic carbon came from dissolution of carbonate debris and early carbonate cements.Distinctiveδ^(13)C/δ^(18)O values manifest that carbonate cements with different types formed in different periods,which make different contributions to the reservoir properties.Calcite/dolomite formed during eodiagenesis(70–90℃)and early mesodiagenesis stage(90–120℃),and were favorable to reservoir owing to their compacted resistance and selective dissolution.Ferrocalcite/ferrodolomite/ankerite formed during middle-late mesodiagenetic stage(above 120℃),and were unfavorable to reservoir due to cementing the residual intergranular pores.Hence,in order to evaluate the reservoir characteristics,it is of significantly important to distinguish different types of carbonate cements and explore their origins.

Complex genesis of multiperiod fractures in the Middle Triassic Leikoupo Formation in the Pengzhou gas field, western Sichuan Basin, China

The cumulative expression of multistage deformation is complex multiperiod fractures,which are commonly seen in tectonic zones.The Middle Triassic Leikoupo Formation in the western Sichuan Basin Depression,China,is a typical marine carbonate reservoir with natural fractures caused mainly by tectonic movements.According to outcrops,drill cores,image logging,and fluid inclusions,the fracture characteristics,types of natural fractures,and interactions of fractures are determined.In total,419 natural fractures in 493.2 m of cores from 7 wells are investigated,which are mainly shear and tensile fractures with a small number of weathering generated fractures.Meanwhile,the results of the stable isotope analysis of δ13C and δ18O,as well as the flow fluid inclusion data,reveal four tectonic periods of fractures with different occurrences.Based on the history of regional tectonic evolution,indicating one period of weathering fractures ascribable to stratal uplift and three periods of structural fractures related to the sequential tectonic movements of the Longmenshan fault belt.By analyzing the interaction relationships of fractures,three types of fracture interaction relationships are observed:cutting,restraining,and overlapping.The four stages fractures are chronologically assigned to(1)the early Indosinian N-S trending compression,(2)the late Indosinian NW-SE compression,(3)the middle Yanshanian NE-SE compression,and(4)the early Himalayan E-W compression.The influence of natural fractures on gas migration and well production in marine carbonates is discussed,and indicates that tectonic fractures could provide seepage channels for gas migration and accumulation from near or distant hydrocarbon source rocks into the Middle Triassic Leikoupo Formation.This study utilizes a pragmatic approach for understanding the fracture genesis mechanism in oil and gas field with multiperiod fractures.

Distribution and mechanism of gently dipping fractures subjected to river incision: A case study from Nujiang River, China

Gently dipping fractures subjected to river incision are widely distributed on rock slopes.In this paper,a rock slope on the Nujiang River(China)is investigated to study the role of gently dipping fractures in the rock slopes evolution.Detailed field surveys indicate that gentle fractures are concentrated in four main zones.Moreover,the kinematics of the fracture system suggest that the genesis of these fractures can be synthesized into a progressive evolution model.This model indicates that the joints begin with the formation of an array of en echelon cracks that are subjected to continued crack elongation and shearing before ultimately approaching one another and interacting to form a complex joint system.Geomechanical analysis is performed to reveal the mechanisms of this genesis,and three main fracture patterns are identified based on the slope stress and are classified with respect to the slope evolution.Based on the detail field investigations and the evolutionary history of the river valley,we propose that intermittent incision by the river was the main factor contributing to the concentrated distribution of gently dipping joints.

从陆缘伸展探讨新生代南海构造演化

南海的形成和演化是地学界长期争论的问题,前人给出了多种成因模式,目前较流行的模式是海底扩张,但它难以合理解释南海海底扩张中的洋中脊跳跃现象及南海大洋中的大陆残片。基于欧亚东缘的陆缘伸展,从地幔上涌和陆壳沿莫霍面的重力滑移的新大陆漂移模型出发,通过横跨南海的几条地震勘探剖面的地质新解释,研究了南海的形成和演化过程。结果说明,南海的形成是一种“构造被动挤出+微陆块主动漂移”模式。构造被动挤出是指印度-欧亚碰撞造成的欧亚大陆东南缘的微陆块被大规模挤出,而由陆缘伸展形成的微陆块在被挤出后发生了主动裂解漂移,南海的海底扩张现象是诸多微陆块主动漂移的结果。这个新的模式能够合理地解释南海形成过程中的洋中脊跳跃现象及南海中大陆残片的成因机制。进一步恢复了南海演化过程中周边陆块的运动演化历史,说明欧亚东缘在中生代晚期发生的大规模伸展构造运动是南海形成的基础,新生代印度-欧亚碰撞是南海形成的直接动力,微陆块的裂解漂移是南海形成的主要参与者。

铜陵新桥层状菱铁矿成因的矿物学证据及成矿意义

安徽铜陵新桥矿区二叠系栖霞组底部和石炭系黄龙组—船山组之间产出层状、似层状菱铁矿矿层。开展菱铁矿矿层成因研究对于深入剖析区域层控矽卡岩型铜铁矿床成矿机制具有重要意义。本文利用粉晶X射线衍射(XRD)、扫描电镜(SEM)对菱铁矿矿石进行矿物学研究,结果发现菱铁矿矿石主要由菱铁矿、石英、伊利石和有机质等组成,菱铁矿颗粒粒径较小,表面具有成岩自生的自形石英硬模的微结构,SEM原位微区成分分析显示菱铁矿中除了主量元素铁,还含有大量的锰、锌和钙。矿石中存在两种微结构和不同成因的石英:表面具菱铁矿硬模和次生加大结构的碎屑石英;具六方双锥、单锥以及生物成因球形的自生石英。菱铁矿矿石的组成和矿物表面微结构表明其为沉积成因,非岩浆热液起源。富有机质和亚铁的沉积菱铁矿层和沉积胶状黄铁矿层协同作用,可能是铜陵地区乃至长江中下游成矿带层状铜铁矿床层控性重要制约因素,以及可能作为燕山期中酸岩浆演化的氧化性含铜成矿流体卸载成矿的地球化学还原障。

还原性矽卡岩型金矿床基本特征、研究现状及在中国前景

还原性矽卡岩型金矿以独立金矿形式赋存于钙质沉积岩中,以金品位高(5~15 g/t)著称。目前,该类型金矿的总体研究程度较低,在成矿背景、还原性岩浆源区及成因、金高效富集机制等方面仍缺乏理解。笔者对该类型金矿的地质特征、时空分布规律、成矿机理、找矿标识等方面进行了系统梳理,探讨了该类金矿的研究难点及其在中国的成矿潜力和找矿前景。还原性矽卡岩型金矿具有以下特征:(1)独特的Au-Bi-Te-As±Co元素组合,缺乏Cu等贱金属;(2)矽卡岩以钙铁辉石为主,其次为石榴子石;(3)成矿岩体属于还原性钛铁矿系列,包括辉长闪长岩、闪长岩和花岗闪长岩等;(4)代表性低硫逸度的金属矿物,包括斜方砷铁矿、黑铋金矿、贫S的Te-Bi矿物。关键问题或薄弱环节主要有:(1)还原性岩浆存在温度、盐度、氧逸度、硫逸度、含水量、还原性组分类型及含量等多种属性,这些属性对还原性矽卡岩型金矿的形成有哪些影响?(2) Au可能以氯络合物、硫络合物、Bi-Te熔体、纳米絮状物等多种方式运移,还原性岩浆流体中Au的高效迁移及富集方式有哪些?(3)还原性成矿岩浆的氧化-还原性质有争议,部分学者认为岩浆始终为还原性,另一些学者认为母岩浆为氧化性,后期混入还原性物质;(4)存在深部W-Mo矿化、浅部Au-Sb-Bi矿化的金属元素分带现象,这种分带规律受哪些因素控制?总之,还原性矽卡岩型金矿在中国有着良好的成矿潜力和找矿前景,其中中国东部W/Sn成矿区(带)和Au成矿区(带)的叠加区域、西部还原性岩体分布区是该类金矿的有利勘探区。

隧道突出气体特征及形成机理研究

为研究高原隧道不明突出气体特征及形成机理,本文采用资料收集、现场调查测试与监测、室内岩石学、地球化学试验等方法与手段,研究突出气体赋存地质环境,揭示突出气体成分、演化过程及演化规律,结合区域地质条件演化过程,建立突出气体形成、演化模式。研究结果表明:(1)该横洞及周边地区不具备发育大规模油气资源的岩性条件,该突出气体应属有机成因与无机成因混合气范畴;(2)突出气体含量随时间呈逐渐减小趋势,气体储量有限,不具有易燃性,具有微~中等腐蚀性;(3)该横洞突出气体是一类成分多样、形成演化过程复杂的有机成因和无机成因混合气,其形成先后经历有机成因阶段与无机成因阶段,区域地质历史时期活跃的岩浆活动和出气孔处发育的碳酸盐岩为突出气体的无机成因提供了证据。研究成果可为类似高原隧道突出气体研究和评价提供参考。

鸭寨水库坝址左侧边坡变形机制分析

鸭寨水库坝址左岸边坡为土质边坡,覆盖层成因复杂,物质组成不均,透水性及水理性差异较大。边坡开挖过程中出现开裂变形,通过分析边坡变形破坏迹象、位移监测特征及地质结构、水文地质条件等,采用三维地质建模、土层精细编录等工作,查明边坡变形破坏模式,分析边坡变形成因机制,为设计永久支护措施提供依据。

松辽盆地富氢天然气地质调查与研究

氢能是全球能源转型发展的重要载体,与人工制氢相比,天然氢气的开采不仅具有成本上的优势,也是实现能源完全脱碳的关键。松辽盆地作为大型陆内裂谷盆地,具备勘探天然氢气的潜力。首次系统梳理松辽盆地北部中下部含油气组合和深部含气组合中天然氢的含量,分析天然氢气的空间分布特征,初步探讨了天然氢气的来源、形成机制及控制因素。结果表明:松辽盆地含氢天然气(φ(H_(2))>1.0%)在中央坳陷区普遍发育,氢体积分数为1.00%~85.54%,其中富氢天然气(φ(H_(2))>10.0%)主要在深部含气组合,试气产量在微量和1444 m^(3)/d之间,沿控陷断裂附近分布;松辽盆地天然氢气主要来源于深部富铁岩层的水-岩作用,氢气的形成和供给具有可持续性,具备形成天然氢气聚集的物质基础;基底以上富氢气藏的形成受沟通至地幔的控陷断裂、深大断裂控制,油藏和天然气藏对富氢气体有稀释和破坏作用,未来天然氢气藏的勘探应该避开油气充注的有利区;深化对盆地深部壳-幔结构及无机地球化学作用过程的认识,是未来松辽盆地天然氢气勘探的重要科学议题。研究成果可为松辽盆地天然氢气的勘探提供理论指导。

普光地区下三叠统富锂钾卤水成因与分布规律

通过对普光地区钻孔卤水和油田水水化学分析测试,开展离子比例研究,明确嘉陵江组和飞仙关组各亚段卤水的成因机制和分布规律。研究结果表明:嘉陵江组卤水K^(+)质量浓度在4060.00~20160.00 mg/L,Li^(+)质量浓度在26.00~271.00 mg/L,整体为海水浓缩特征。嘉四段—嘉五段卤水K^(+)质量浓度在4110.00~20160.00 mg/L,Li^(+)质量浓度在76.15~271.00 mg/L,Li^(+),K^(+)富集受海水蒸发浓缩、“绿豆岩”风化作用和淋滤作用主控;嘉二段卤水K^(+)质量浓度在4060.00~4140.00 mg/L,Li^(+)质量浓度在26.00~27.80 mg/L,受海水蒸发浓缩及膏盐溶解主控。飞仙关组卤水K^(+)质量浓度在6.13~650.00 mg/L,Li^(+)质量浓度在0.02~50.60 mg/L,整体为地下溶滤特征。飞三段—飞四段卤水K^(+)质量浓度在588.00~650.00 mg/L,Li^(+)质量浓度在40.40~50.60 mg/L,Li^(+),K^(+)富集受膏岩等围岩溶滤和嘉陵江组卤水运移主控;飞一段—飞二段卤水K^(+)质量浓度在6.13~478.00 mg/L,Li^(+)质量浓度在0.02~17.90 mg/L,由地层水对碳酸盐岩溶解主控。富锂钾卤水平面上主要分布在大湾-土主构造及其构造作用中等的翼部。

渤海A油田馆陶组低阻油层成因机理研究及流体性质识别新方法

低阻油层作为一种非常规、隐蔽性强的特殊油层,勘探潜力巨大。研究区低阻油层的形成受多重因素的影响,测井响应特征在油水层的对比度较低,造成测井解释困难。为此,首先从宏观和微观两个方面深入分析低阻油层的成因机理;其次,将测井、气测录井以及生产开发资料相结合,针对研究区气测烃组分数据的特点,改进了含油气丰度计算方法用以定量识别低阻油层。结果表明:弱水动力环境和压实作用是低阻油层的宏观成因,孔隙结构复杂导致的高束缚水饱和度是普遍微观成因,天然淡水水淹成藏模式导致的油水层矿化度差异是主控成因。改进的含油气丰度能够有效定量的识别研究区低阻油层,解释符合率达到84.7%,可以为渤海A油田低阻油层的挖潜工作提供定量依据。

美国典型富氦无机成因气田中氦气地质特征与聚集机制

美国广泛发育具有经济效益的富氦无机成因天然气田,如其中富氦氮气田甚至可以含有高达10%的氦。原地和周边地区的基底提供充足的氦源而氮气可来自不同圈层,且通常N_(2)/He(He>0.1%)在5~50之间。但是富氦氮气田在美国独特地质环境之外是否也有发现还需要进一步的研究。富氦二氧化碳气田中的氦主要也来自壳源且产量可观。科罗拉多高原上的富氦二氧化碳气田均被认为是来源于新生代晚期的岩浆活动,且该地区岩浆岩具有较高的U、Th含量。地下水溶气脱气-再溶解(Groundwater Gas Stripping and Re-dissolution,GGS-R)模型被普遍认为可以合理解释CO_(2)气藏中氮气、氦等惰性气体的聚集成藏机制。具体来说,幔源CO_(2)载体气充注时将溶解在地下水中的大气源惰性气体与壳源惰性气体脱出成藏,并与地下水达到水/气溶解平衡。虽然不同气田的平衡值各有不同,但是科罗拉多高原上的各气田均显示出相似的范围值,即在相应的储层压力和温度下为0~100 cm^(3)水/cm^(3)气。本文系统分析美国无机成因富氦气藏的氦气生成、运移和聚集机制,讨论氦气在经历氦源岩内游离相扩散初次运移后通过水溶相、气容相集流或是多相渗流方式进行的二次运移及由无机成因载体气N_(2)和CO_(2)共同参与的富集成藏机制,既可为我国氦气勘查提供理论认识依据,也可为二氧化碳地质评价和开发利用及安全封存提供参考。

庐枞盆地西湾铅锌矿床黄铁矿微量元素组成特征及成矿启示

黄铁矿作为铅锌矿床中最常见的金属硫化物之一,是铅锌矿床形成过程中的贯通性矿物,其矿物学与地球化学特征可探究成矿作用过程,进而探讨矿床成因。庐枞盆地是长江中下游多金属成矿带的重要组成部分,近年来在其北缘新发现了可达大型规模的西湾铅锌矿床。虽然前人对西湾铅锌矿床已开展了相关的研究,但对与成矿关系密切的黄铁矿化学组成及其成因等方面的研究还较为薄弱。本研究首次利用偏反光显微镜与激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)对该矿床多类黄铁矿开展研究,揭示黄铁矿微量元素组成特征和替换机制,进一步探讨矿床成因。结果显示,根据晶体形态及矿物组合特征将黄铁矿分为成矿前与成矿期两期。成矿前黄铁矿主要呈半自形-它形粒状结构,粒径为10~50μm,可见多个细小颗粒组成粒状集合体,其特征元素主要为Cu、Ag、As、Pb、Sb;而成矿期黄铁矿主要呈自形-半自形粒状结构,粒径大于200μm,通常和方铅矿、闪锌矿组合,呈脉状的形式产出于灰岩裂隙中,其特征元素主要为Mn、Co、Ni、Zn、Cs、Cd、In、Sn。黄铁矿中微量元素替代机制主要为单元素和多元素耦合替代,其中单元素替代机制主要有Co^(2+)↔Fe^(2+)、Ni^(2+)↔Fe^(2+)、Pb^(2+)↔Fe^(2+),多元素耦合替代机制主要有As^(3+)+Ag+↔2Fe^(2+)、(Tl++Cu++Ag+)+(Sb^(3+),As^(3+))↔3Fe^(2+),此外,还有部分Pb、Zn、As以方铅矿、闪锌矿和砷黄铁矿等微小包裹体的形式存在于黄铁矿晶体中。黄铁矿中Co、Ni、As、Cu、Mn、Ge、Ag等微量元素组成特征与矽卡岩型铅锌矿床类似,结合前人研究成果,认为西湾铅锌矿床属于远源矽卡岩型矿床。

朝阳盆地白垩系九佛堂组火山沉积作用及其对有机质富集的影响

辽西朝阳盆地位于燕山构造带东段,属于松辽外围中生代的断陷盆地,勘探认识程度不高。前人研究认为,朝阳盆地下白垩统九佛堂组为湖相沉积,而忽略了火山事件对于湖盆沉积的重要影响。对此笔者通过区域地质资料调查、钻井岩心描述、岩心薄片资料观察以及分析测试资料等手段,在火山碎屑岩分类基础上,根据火山碎屑含量划分出沉积火山碎屑岩以及火山碎屑沉积岩,并结合粒度、组分、沉积构造等特征细分出11种岩相类型以及9种岩相组合,进而提出火山碎屑流、火山异重流、火山灰异轻流、热液侵入和微生物诱导5种成因机制。结合钻井岩心观察识别出火山沉积序列及沉积特征,建立了朝阳盆地九佛堂组火山湖泊沉积模式,为研究区油气资源的勘探开发提供理论依据。研究发现,火山物质对湖盆内有机质富集起到积极的影响。朝阳盆地九佛堂组烃源岩地化测试显示:含有火山细粒物质参与沉积的样品有机质丰度指标更好,有机质更富集。由于燕山构造带内其他盆地同样具有相似的火山活动地质背景,研究结果也为这些地区沉积学及油气资源研究起到良好的对比参照作用。

二连盆地富气凹陷低阶煤煤层气成因及成藏机制

内蒙古低阶煤煤层气资源丰富,煤层气成因与成藏机制研究对低阶煤煤层气资源选区评价至关重要。以二连盆地重点富气凹陷低阶煤煤层气为研究目标,利用煤层气组分、碳/氢同位素、煤层水水质、氢/氧同位素及放射性同位素^(3)H和^(14)C测试等多种实验手段,分析煤层气、水地球化学特征,揭示低阶煤煤层气成因来源及成藏机制。结果表明,二连盆地煤层气组分以甲烷为主,均为干气,其中甲烷体积分数随埋深增加而增大,CO_(2)体积分数随埋深增加呈先增加后降低趋势,在300~500 m范围出现高值区。甲烷碳、氢同位素普遍偏轻,δ^(13)C(CH_(4))分布在-70.3‰~-48.0‰,δD(CH_(4))分布在-285.5‰~-189.0‰,δ^(13)C(CO_(2))在-37.6‰~1.94‰变化。煤层水化学类型主要为HCO_(3)-Na型和Cl·HCO_(3)-Na型,现今煤层水体环境较为稳定,水动力较弱,煤层水表观年龄在1020~47490 a,主要来源于第四纪大气降水,没有或较少有现今地表水补给。二连盆地煤层气主要为原生生物成因气,混有少量早期热成因气,随着埋深加大,地层环境和产甲烷古菌类型发生变化,生物甲烷生成途径发生转变。其中吉尔嘎朗图凹陷早期以乙酸发酵产气为主,晚期转变为CO_(2)还原产气为主,并混有少量低熟热成因气;巴彦花和霍林河凹陷微生物产气途径均以乙酸发酵为主,其中霍林河凹陷还混有少量甲基发酵型生物气。研究区具有适合生物气生成的低地温、低矿化度和低热演化程度的“三低”煤层条件,其中,吉尔嘎朗图凹陷属于地堑式浅部厚煤层生物气成藏模式,巴彦花和霍林河凹陷属于半地堑式中深部承压区水力封堵生物气成藏模式。寻找适合生物成因气形成和富集的有利目标区,应是二连盆地煤层气未来勘探开发的重点方向,也是二连盆地低阶煤煤层气增储上产的现实保障。

Hydrochemical insights on the signatures and genesis of water resources in a high-altitude city on the Qinghai-Xizang Plateau, South-west China

Water resources have crucial implications for the steady development of the urban social economy.This study investigated the hydrochemical signatures and genesis of water resources in the urban area of Lhasa City(UALC).To this end,several analyses,such as ion ratio analysis and correlation analysis,were performed by comprehensively applying mathematical statistics and integrated hydrochemical methods.The results show relatively low concentrations of major ions in the groundwater and surface water(GSW)of the UALC.The primary anions and cations are HCO3-and Ca2+,reflecting the HCOg-Ca water type.Nevertheless,groundwater exhibits higher concentrations of key chemical components compared to surface water.GsW are weakly alkaline,with pH values of 7.78 and 7.61,respectively,and they have low salinity with average concentrations of total dissolved solids being 190.74 and 112.17 mg/L,respectively.Anthropogenic inputs have minimal influence on the hydrochemical features of GSw,whereas rock weathering is the dominant controlling factor.Furthermore,cation exchange.is a significant hydrogeochemical.process influencing their hydrochemical features.According to the isotope analysis(H and 180),the primary source of recharge for GSW is atmospheric precipitation,with some input from melted ice and snow.Moreover,GSW samples from the UALC show relatively similar 2H and 18O isotopic compositions,indicating the existence of a discernible hydraulic connection linking the two water sources.The research findings can serve as a valuable scientific reference and foundation for the sustainable development,effective utilization,and proper safeguarding of regional water resources in high-altitude areas.

Two stages power generation test of the hot dry rock exploration and production demonstration project in the Gonghe Basin,northeastern Qinghai-Tibet plateau,China

The Hot Dry Rock(HDR)is considered as a clean and renewable energy,poised to significantly contribute to the global energy decarbonization agenda.Many HDR projects worldwide have accumulated valuable experience in efficient drilling and completion,reservoir construction,and fracture simulation.In 2019,China Geological Survey(CGS)initiated a demonstration project of HDR exploration and production in the Gonghe Basin,aiming to overcome the setbacks faced by HDR projects.Over the ensuing four years,the Gonghe HDR project achieved the first power generation in 2021,followed by the second power generation test in 2022.After establishing the primary well group in the initial phase,two directional wells and one branch well were drilled.Noteworthy progress was made in successfully constructing the targeted reservoir,realizing inter-well connectivity,power generation and grid connection,implementing of the real-time micro-seismic monitoring.A closed-loop technical validation of the HDR exploration and production was completed.However,many technical challenges remain in the process of HDR industrialization,such as reservoir fracture network characterization,efficient drilling and completion,multiple fracturing treatment,continuous injection and production,as well as mitigation of induced seismicity and numerical simulation technology.