Natural gas characteristics and gas-source comparisons of the Lower Triassic Feixianguan Formation,Eastern Sichuan Basin,China

There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feix-ianguan Formation in the Eastern Sichuan Basin.This seriously restricts the study of natural gas dy-namics in the Feixianguan Formation and thus hampers natural gas exploration in the region,so further study is urgently required.Using experimental tests of natural gas composition,stable isotopes,and noble gas isotopes with gas chromatography(GC)and mass spectrometry(MS)studies of source rock and reservoir asphalt saturated hydrocarbons,the natural gas geochemical characteristics,the genetic identification and a gas-source comparison of the Feixianguan Formation were studied.Then,con-strained by the thermal history,the histories of gas generation and expulsion were restored by basin simulation technology.Finally,a gas accumulation model was established for the Feixianguan Formation.The results showed that(1)the H_(2)S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin,respectively.The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs.(2)The natural gas of the Feixianguan Formation is organic thermogenic gas,which is mainly oil-type gas generated by the secondary cracking of crude oil.The gas-generating parent material is mainly type II kerogen.(3)The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argil-laceous source rocks of the Upper Permian Longtan Formation.(4)Natural gas accumulation occurred as follows:the paleo-structure heights were filled with crude oil in the Early Jurassic,and paleo-oil res-ervoirs were formed in the Feixianguan Formation;during the Middle-Late Jurassic,the paleo-oil res-ervoirs were cracked when the reservoir temperatures rose above 160 C,and paleo-gas reservoirs were formed.Since the end of the Late Jurassic,the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs.These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.

A study on the genetic relations between Permian Longtan Formation coal series strata and Carlin-type gold deposits,southwestern Guizhou Province,China

A large number of the Carlin-type gold deposits occur in the Longtan Formation in southwestern Guizhou Province.The Long-tan Formation contains abundant basalt,tuff and siliceous rocks.All rocks of the Longtan Formation are enriched in gold,which were deposited in a limited platform environment in the transition zone from marine to continental.The process of sedimentation was accompanied by the eruption of Emeishan basalt and hydrothermal deposition controlled by co-sedimentary submarine deep faults in the west,which led to the formation of a peculiar gold-bearing formation with coal series strata.This formation controlled the occurrence of the Carlin-type gold deposits in southwestern Guizhou Province.In response to the remobilization of the Emei mantle plume during the Yanshanian period,As,Au and other ore-forming materials were continuously extracted by deeply circulating waters from the Emeishan basalt and coal seams,thereafter forming ore-forming hydrothermal solutions.When these elements were transported in the coal seams,large amounts of As,Au and other elements were enriched in pyrite within the coal seams,thus forming high-As coal and Carlin-type gold deposits in the Longtan Formation coal series strata.

Sedimentary Facies and Coal Accumulation of the Northern Type Longtan Formation in Central Hunan,Southern China

The northern type Longtan Formation of the Late Permian in central Hunan is dominated by an assemblage of greyish black mudstone,siltstone, sandy mudstone,fine sandstone and coals,and contains a variety of sedimentary structures such as thin sandstone-mudstone interbedded bedding,flaser beddings,lenticular beddings,horizontal

Lithofacies and pore features of marine-continental transitional shale and gas enrichment conditions of favorable lithofacies:A case study of Permian Longtan Formation in the Lintanchang area,southeast of Sichuan Basin,SW China

In this work,the Permian Longtan marine-continental transitional shale in the southeast of Sichuan Basin was taken as study object.Through petrology and geochemical analysis,lithofacies types of the marine-continental transitional shale were classified,key controlling factors of physical properties and gas content of the different shale lithofacies were analyzed.The research results show that the Longtan Formation marine-continental transitional shale in the study area has four types of lithofacies,namely,organic-lean calcareous shale,organic-lean mixed shale,organic-lean argillaceous shale,and organic-rich argillaceous shale,among which the organic-rich argillaceous shale is the most favorable lithofacies of the study area.The pore types of different lithofacies vary significantly and the clay mineral-related pore is the dominant type of the pore system in the study area.The main controlling factor of the physical properties is clay mineral content,and the most important factor affecting gas content is TOC content.Compared with marine shale,the marine-continental transitional shale has low average values,wide distribution range,and strong heterogeneity in TOC content,porosity,and pore structure parameters,but still contains some favorable layers with high physical properties and gas contents.The organic-rich clay shale deposited in tidal flat-lagoon system is most likely to form shale gas sweet spots,so it should be paid more attention in shale gas exploration.

川东地区龙潭组页岩岩性序列及勘探意义

川东地区龙潭组具有较大的页岩气勘探前景,该地层沉积于海陆过渡环境,沉积相变化快,岩性复杂,存在难以通过常规的矿物成分方法划分岩相以及当前岩相划分尚不精确的问题,制约了该地区龙潭组页岩有利岩相带识别及勘探。本文基于岩心观察、野外剖面实测和薄片鉴定,结合钻井的泥地比、单层岩性厚度,建立了川东地区龙潭组7种特征岩性组合模式(泥页岩型、富泥含砂型、富泥含灰型、灰泥互层型、富灰含泥型、致密灰岩型和火成岩型);综合TOC、孔隙度、含气性、脆性指数等页岩储层特征参数,明确了不同岩性组合在龙潭组各段的平面分布规律。研究表明,纵向上优势岩性组合主要为龙潭一段富泥含灰型和泥页岩型,龙潭二段主要为泥页岩型、灰泥互层型和富泥含灰型。平面上龙潭一段优势岩性组合富泥含灰型主要分布在开州—云阳一带,泥页岩型主要分布在重庆—綦江一带;龙潭二段优势岩性组合泥页岩型分布在巴南—綦江一带,灰泥互层型分布在达州一带,富泥含灰型分布在万州—梁平—石柱一带。该项研究成果为川东地区龙潭组页岩气勘探提供了重要依据。

川东二叠系龙潭组不同沉积环境下的页岩弹性波速度特征

笔者选取川东地区FT1井龙潭组页岩进行实验测试,在岩相划分的背景下,通过主微量元素研究川东龙潭组不同岩相的沉积环境,结合沉积环境对石英成因、TOC的影响,探讨不同沉积环境下的弹性波速度变化特征。研究结果表明:①混合质页岩和黏土质页岩处于低古生产力、富氧、陆源碎屑输入较高的沉积环境,其石英以陆源碎屑石英为主,TOC含量偏低;硅质页岩处于高古生产力、缺氧、陆源碎屑输入较低的沉积环境,其石英以生物成因石英为主,TOC含量较高。②混合质页岩和黏土质页岩以黏土颗粒作为岩石骨架,弹性波速度较低,且弹性波速度随石英含量呈上升趋势;硅质页岩以石英颗粒作为岩石骨架,弹性波速度较高,且弹性波速度随石英含量呈下降趋势。研究结果可为龙潭组页岩优势岩相勘探提供依据。

重庆地区二叠系龙潭组煤系地层非常规气地质特征分析

为探索重庆地区二叠系龙潭组煤系地层非常规气地质特征,基于区内煤田勘查、煤层(系)气勘查取得的地质资料及测试数据,对二叠系龙潭组煤系地层煤储层、暗色泥页岩储层、致密砂岩储层基本特征进行分析总结。研究表明,区内煤储层具有煤体结构以碎裂—块状为主、埋深中等、孔隙不发育、低孔低渗、含气量高的特点;暗色泥页岩储层具有低脆性、单层厚度薄、孔隙不发育、低孔低渗、含气量一般的特点;致密砂岩储层具有单层厚度薄、孔隙不发育、低孔低渗、含气性一般的特点。若考虑组合开发,具备一定的开发前景。

渝南地区二叠系龙潭组C_(25)煤层煤层气基础地质条件分析

渝南地区二叠系龙潭组煤层气勘探开发处于起步阶段,为揭示该区主力煤层C_(25)的煤层气基础地质条件,基于区内煤田钻孔、煤层气钻井获取的地质资料和实验测试数据,对煤岩煤质、煤层孔渗、含气性等特征进行了分析。结果表明:研究区二叠系龙潭组C_(25)煤层具有“发育稳定、厚度相对大、孔渗低、变质程度高、含气量高”的特征。C_(25)煤层全区发育稳定,呈“北厚南薄”的趋势,北部一般大于1.5 m;煤岩煤质属于半亮型煤;有机组分中镜质组含量介于51.7%~72.2%;镜质组最大反射率整体介于1.8%~2.2%,变质程度处于高成熟—过成熟阶段;煤岩孔渗较差,孔隙度介于3.46%~8.46%,渗透率大多低于0.01×10^(-3)µm^(2);含气性好,一般大于10.0 m^(3)/t;同时,煤层顶底板均为良好封隔层。结合綦煤1井、Y2井产气效果,认为渝南地区二叠系龙潭组C_(25)煤层具备较好的煤层气勘探开发基础地质条件。

川东南南川区块龙潭组深部煤层气成藏特征及勘探前景

四川盆地东南缘南川区块Y2井直井自喷日产气1.3×104m^(3),获四川盆地东南缘深部煤层气勘探战略突破。为了系统揭示南川区块深部煤层气富集高产规律,通过区域地质、测试、化验及生产资料,从煤岩煤质、孔裂隙发育特征、含气性、可压性入手,开展深部煤层气成藏特征及勘探潜力评价。结果表明:研究区深部煤储层全区稳定分布,厚度在1.5~4.2 m,镜质体随机反射率Rran在1.6%~2.2%,为高镜质组含量、低灰分煤层,为煤层气成藏提供了物质基础;煤储层为“微孔-微裂隙”型储层,微孔占比达78.4%,其比表面积贡献达95%,利于煤层气吸附与保存,微裂隙发育,利于压裂改造及气体渗流;煤层具有“高含气量、富含游离气”的特征,总含气量12~37m^(3)/t,深部煤层气游离气占比一般在24%~36%,吸附临界转换深度在1500m左右;深部煤层水平应力差异系数小,煤体结构好,顶板为良好的应力隔档,天然裂缝与最大主应力夹角小,具有良好的可压性;丁山、林滩场等盆缘宽缓背斜及盆内高陡背斜是川东南深部煤层气勘探的有利区带。研究成果对川东南深部煤层气勘探具有重要的指导作用,也可为全国类似盆地深部煤层气勘探提供借鉴。

川南兴文地区上二叠统龙潭组黏土岩锂的富集特征及赋存状态

四川南部位于二叠纪峨眉山大火山岩省中—外带,广泛分布与火成岩风化-沉积有关的上二叠统龙潭组黏土岩,具有形成锂等关键金属矿产资源的地质背景和成矿条件。本文对川南兴文地区上二叠统龙潭组下部黏土岩进行了较为系统的地质调查,对研究区以及钻孔岩芯样品进行了化学分析,以确定黏土岩中锂等元素的分布特征及富集规律。在此基础上,利用粉晶X-射线衍射(XRD)分析了富锂黏土岩的矿物组成,采用聚焦离子束飞行时间二次离子质谱仪(FIB-TOF-SIMS)分析了富锂黏土岩微米尺度上的元素分布特征。结果表明,龙潭组下部黏土岩中富集Li以及Ga、Nb等元素,是一个多种关键金属的富集层,具有良好的成矿潜力和找矿前景。本区黏土岩来源于峨眉山大火山岩省火山岩的风化产物,富锂的矿层主要为含黄铁矿高岭石黏土岩,其沉积成岩环境为海陆过渡地区的潟湖还原咸水环境,Li含量与化学风化强度(CIA指数)密切相关,具有风化-沉积型矿床的特征。富锂黏土岩中锂除少量赋存于锂云母之中外,主要是被吸附于黏土岩的蒙脱石相中,部分进入蒙脱石矿物结构,还有一部分赋存于伊利石中。Li除了来自火山岩的风化释放以外,部分还可能来自滨海浅层地下卤水的直接补给,从而形成含锂云母的高品位的富锂黏土岩。

安徽省宣城地区龙潭组页岩孔隙发育特征及其影响因素

安徽省宣城地区上二叠统龙潭组页岩气资源潜力大,已有钻井揭示其页岩含气性差异大,页岩气赋存富集机理复杂。通过总有机碳含量分析、岩石热解实验、X衍射、低温液氮吸附、二氧化碳吸附和场发射扫描电镜观测等手段,研究宣城地区龙潭组页岩中孔隙的大小、结构及类型,探讨影响其孔隙发育的主要因素。研究表明:(1)宣城地区龙潭组页岩中孔隙主要为半开放型,并且存在一定量的细颈瓶孔。其中,矿物孔较发育,主要为微米孔,孔隙数量多;有机孔发育数量较少,孔径为纳米级—微米级。(2)龙潭组页岩BET比表面积为4.2601~10.3068 m^(2)/g,平均为7.4290 m^(2)/g。介孔+宏孔体积为0.0049~0.0179 cm^(3)/g,平均为0.0089 cm^(3)/g;微孔体积为0.0019~0.0038 cm^(3)/g,平均为0.0026 cm^(3)/g。孔径大于10 nm的孔隙是页岩孔隙体积的主要贡献者。(3)高演化、矿物含量差异大等使得宣城地区龙潭组页岩孔隙发育规律性变得复杂,TOC含量和矿物含量明显影响着宣城地区龙潭组页岩孔隙体积,但与孔隙比表面积没有明显线性相关性。在宣城地区龙潭组页岩气后续勘探开发中,应注重较高TOC含量、较高碳酸盐矿物含量和较低黏土矿物含量的页岩。

贵州金沙煤矿东部晚二叠世龙潭组底部铝土质泥岩中镓富集规律及找矿前景

研究区位于金沙县东部,龙潭组底部铝土质泥岩中镓含量为24.7269.38 ug/g,平均43.87 ug/g。通过相关关系法,分析了Ga与SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)、TiO_(2)的相关关系,其中Ga与SiO_(2)呈中负相关,与Al_(2)O_(3)+Fe_(2)O_(3)+TiO_(2)呈强正相关,表明镓在风化、搬运和沉积过程中更容易追随Al与Ti,主要以离子吸附态或以氢氧化物胶体方式赋存。根据含镓岩系岩性、沉积构造及化石特征,富铝粘土岩系沉积时期由下至上古水深为深-浅-深,氧化还原环境为还原-弱氧化-还原环境,风化作用相对弱-强-相对弱的变化规律。结合大地构造背景,镓的富集有利区为滨海平原及低洼地带,主要经历源岩风化-搬运-再风化淋滤过程。研究区北东部田湾煤矿-沙土-中心一带含矿品位高,为找矿前景区。

川南地区二叠系黏土型锂矿地质特征及找矿潜力

近年来,世界各国为了力争实现《巴黎协定》所设立的环境保护目标,就加强绿色经济可持续发展达成了共识,在此背景下世界各主要经济体先后推出相关政策和行动以推动本国能源结构转型发展,从而推动了锂等新能源产业快速发展(邢凯等,2022)。锂享有“白色石油”和“21世纪最有应用潜力的金属”等美誉.

渝东南地区龙潭组煤层气高效压裂及排采工艺探索

渝东南地区面临煤层改造不充分、排采见气周期长、产量低等问题。为提高气井开发效率,以该地区D1井龙潭组开发为例,采用以“远支撑”为核心理念的大排量、大规模、多轮次压裂技术体系进行储层改造试验,并辅以“快排上产、达产稳压”排采工作制度。研究结果表明,此压裂技术的应用可显著改善储层导流能力,压完即见气,且在快速返排过程中气量日趋上涨,直至稳定于5000 m^(3)/d以上。

贵州织金文家坝地区铝土质泥岩成因分析

该文以贵州织金文家坝龙潭组下段铝土质泥岩为研究对象,结合沉积学、岩石学、地层学、矿床学、地球化学等理论和方法,划分了区域内龙潭组沉积相类型,认为铝土质泥岩为峨眉山玄武岩风化产物,经历了三个阶段的铝富集,但因峨眉山玄武岩风化作用不彻底,风化物中铝含量少,成岩后没有受构造运动抬升地表经受风化淋滤而未形成铝土矿。

湖北襄阳地区龙潭组富锂黏土岩地球化学特征及其对物源和古沉积环境的指示

湖北襄阳地区二叠系龙潭组底部发育一套富锂黏土岩,其形成的古环境条件对黏土型锂矿找矿勘查具有重要指示作用。采集大坪矿区的龙潭组黏土岩样品,通过主量、微量和稀土元素分析,恢复黏土岩的古沉积环境和物源。结果表明,大坪矿区龙潭组黏土岩SiO_(2)含量为22.38%~41.08%,Al_(2)O_(3)含量为19.36%~34.80%,TFe_(2)O_(3)含量为1.36%~25.62%,整体呈现富硅、富铝、富铁的特征;Li_(2)O含量与累托石(r=0.738)、Cu(r=0.594)、Zn(r=0.724)具有较强的正相关性;Sr/Ba比值主要为2.62~14.00,指示古盐度为海相咸水;V/Cr比值为0.535~1.84,V/(V+Ni)比值为0.77~0.99,δCe为1.04~1.67,说明其沉积时属于还原环境;Sr/Cu比值为4.14~11.27,CIA值为76.20~88.11,指示古气候趋向于温暖或炎热的潮湿环境,物源区风化强烈。结合区域地质演化史,推断物源可能为勉略缝合带和南秦岭构造带中形成的与俯冲有关的岩浆岩,以及淮阳古陆出露的碳酸盐岩。在襄阳地区可以充分利用前人累托石黏土矿勘查成果,推进龙潭组黏土型锂矿的找矿勘查工作。

Geological characteristics and co-exploration and co-production methods of Upper Permian Longtan coal measure gas in Yangmeishu Syncline, Western Guizhou Province, China

Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.

川南兴文地区上二叠统龙潭组下部发现Li、Ga、Nb、REE等关键金属富集层

关键金属是新能源、现代高科技产业及航空航天和国防军工等行业不可或缺的原料,对关键金属矿产的勘查和研究已上升为国家战略(陈骏,2019)。四川南部兴文地区位于扬子陆块西缘,峨眉山大火成岩省外带(图1a),区内广泛分布与二叠纪碳酸盐岩/峨眉山玄武岩风化有关的上二叠统龙潭组(P3lt)黏土岩(图1b),具有形成锂等关键金属资源的地质背景和成矿条件。本次以川南兴文地区龙潭组(P3lt)下部铝质黏土岩为调查研究对象,地质调查工作发现其为Li、Ga、Nb、REE等关键金属的富集层,具有很好的找矿前景。

川南地区二叠系龙潭组页岩储层特征及勘探潜力

二叠系龙潭组是目前四川盆地页岩气勘探开发的新热点层位。通过偏光显微镜鉴定、场发射扫描电镜分析、X射线衍射测试、有机碳含量测定及高压压汞分析、现场解析气实验等手段和方法,对川南地区二叠系龙潭组页岩储层进行了综合研究。研究结果表明:(1)川南地区二叠系龙潭组为一套陆相曲流河沉积,河漫沉积的页岩发育,其矿物成分主要为石英和黏土矿物,含少量碳酸盐矿物。(2)研究区页岩储层主要发育粒间(缘)孔与微裂缝,局部发育粒内孔与溶蚀孔,偶见有机质孔隙,其中黏土矿物层间微裂缝最为发育。孔隙结构表现为以微孔为主,介孔(孔径为2~50 nm)次之,孔径普遍较小,分选较差,孔隙和喉道半径差异较大,非均质性强。(3)研究区页岩储层中煤岩含气量最高,炭质泥岩与泥岩次之,泥质粉砂岩、粉砂岩与细砂岩含气量最低。与龙马溪组页岩储层相比,龙潭组泥岩孔隙度与总含气量更好,渗透率较差,其中炭质泥岩的孔隙度和总含气量最佳。(4)研究区二叠系龙潭组勘探潜力较大,烃源岩中有机质类型主要为Ⅲ型,其次为Ⅱ_(2)型;其R_(o)值平均约为2.8%,达到高熟阶段;TOC含量变化范围大,炭质泥岩中的TOC一般大于15%。(5)川南地区二叠系龙潭组发育河漫平原沉积,富有机质泥页岩分布稳定,具备良好的页岩气形成条件,估算其天然气资源量约为2.4×10^(12)m^(3),有利勘探区主要位于川南古蔺—叙永地区。

四川盆地川西坳陷三叠系盐下超深层油气成藏条件与勘探方向

四川盆地川西坳陷三叠系盐下海相层系埋深普遍超过7000 m,油气勘探程度低,但是油气基本成藏条件优越,具有良好的勘探前景。依据最新的钻探成果和地震资料,系统分析了川西坳陷超深层烃源岩、储层、构造变形样式和油气动态成藏匹配关系,指出了有利勘探方向。研究认为:川西坳陷超深层发育下寒武统筇竹寺组、中二叠统茅口组和上二叠统龙潭组3套区域烃源岩,生烃强度均超过20×10^(8)m^(3)/km^(2),具有形成大、中型油气田的资源潜力。坳陷内发育震旦系灯影组台缘丘滩和二叠系栖霞组、茅口组颗粒滩白云岩储层,受高能相带和多期岩溶作用控制,具有规模性储集体成储基础。山前带推覆体下盘发育盐下准原地背斜构造,山前坳陷带发育高陡断裂和走滑压扭构造,形成了良好的油气圈闭。山前隐伏构造与坳陷内构造-岩性复合圈闭均形成于印支期,与寒武系烃源岩主生烃期及基底断裂活动期具有良好的匹配关系,具备油气早期成藏条件。综合评价认为坳陷内震旦系灯影组台缘带、与基底高陡断裂沟通的二叠系高能相带和山前带推覆体下盘原位构造是下一步勘探有利目标。