Characteristics and discovery significance of the Upper Triassic–Lower Jurassic marine shale oil in Qiangtang Basin,China

Mesozoic marine shale oil was found in the Qiangtang Basin by a large number of hydrocarbon geological surveys and shallow drilling sampling.Based on systematic observation and experimental analysis of outcrop and core samples,the deposition and development conditions and characteristics of marine shale are revealed,the geochemical and reservoir characteristics of marine shale are evaluated,and the layers of marine shale oil in the Mesozoic are determined.The following geological understandings are obtained.First,there are two sets of marine organic-rich shales,the Lower Jurassic Quse Formation and the Upper Triassic Bagong Formation,in the Qiangtang Basin.They are mainly composed of laminated shale with massive mudstone.The laminated organic-rich shale of the Quse Formation is located in the lower part of the stratum,with a thickness of 50–75 m,and mainly distributed in southern Qiangtang Basin and the central-west of northern Qiangtang Basin.The laminated organic-rich shale of the Bagong Formation is located in the middle of the stratum,with a thickness of 250–350 m,and distributed in both northern and southern Qiangtang Basin.Second,the two sets of laminated organic-rich shales develop foliation,and various types of micropores and microfractures.The average content of brittle minerals is 70%,implying a high fracturability.The average porosity is 5.89%,indicating good reservoir physical properties to the level of moderate–good shale oil reservoirs.Third,the organic-rich shale of the Quse Formation contains organic matters of types II1 and II2,with the average TOC of 8.34%,the average content of chloroform bitumen'A'of 0.66%,the average residual hydrocarbon generation potential(S1+S2)of 29.93 mg/g,and the Ro value of 0.9%–1.3%,meeting the standard of high-quality source rock.The organic-rich shale of the Bagong Formation contains mixed organic matters,with the TOC of 0.65%–3.10%and the Ro value of 1.17%–1.59%,meeting the standard of moderate source rock.Fourth,four shallow wells(depth of 50–250 m)with oil shows have been found in the organic shales at 50–90 m in the lower part of the Bagong Formation and 30–75 m in the middle part of the Quse Formation.The crude oil contains a high content of saturated hydrocarbon.Analysis and testing of outcrop and shallow well samples confirm the presence of marine shale oil in the Bagong Formation and the Quse Formation.Good shale oil intervals in the Bagong Formation are observed in layers 18–20 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 206.7 m thick,with the maximum and average(S0+S1)of 1.92 mg/g and 1.81 mg/g,respectively.Good shale oil intervals in the Quse Formation are found in layers 4–8 in the lower part of the section,where the shales with(S0+S1)higher than 1 mg/g are 58.8 m thick,with the maximum and average(S0+S1)of 6.46 mg/g and 2.23 mg/g,respectively.

Geological characteristics and models of fault-foldfracture body in deep tight sandstone of the second member of Upper Triassic Xujiahe Formation in Xinchang structural belt of Sichuan Basin,SW China

In the second member of the Upper Triassic Xujiahe Formation(T_(3)x_(2))in the Xinchang area,western Sichuan Basin,only a low percent of reserves has been recovered,and the geological model of gas reservoir sweet spot remains unclear.Based on a large number of core,field outcrop,test and logging-seismic data,the T_(3)x_(2) gas reservoir in the Xinchang area is examined.The concept of fault-fold-fracture body(FFFB)is proposed,and its types are recognized.The main factors controlling fracture development are identified,and the geological models of FFFB are established.FFFB refers to faults,folds and associated fractures reservoirs.According to the characteristics and genesis,FFFBs can be divided into three types:fault-fracture body,fold-fracture body,and fault-fold body.In the hanging wall of the fault,the closer to the fault,the more developed the effective fractures;the greater the fold amplitude and the closer to the fold hinge plane,the more developed the effective fractures.Two types of geological models of FFFB are established:fault-fold fracture,and matrix storage and permeability.The former can be divided into two subtypes:network fracture,and single structural fracture,and the later can be divided into three subtypes:bedding fracture,low permeability pore,and extremely low permeability pore.The process for evaluating favorable FFFB zones was formed to define favorable development targets and support the well deployment for purpose of high production.The study results provide a reference for the exploration and development of deep tight sandstone oil and gas reservoirs in China.

Coal petrology,sedimentology and depositional environment of the Parvadeh coais in the Upper Triassic,Tabas Block of Central-East Iran

Peat forming environment strongly influences the economic value of any coal seam and coal-bearing strata.Hence,pal-aeoenvironmental studies provide important information for coal resource exploration.In this context,detailed studies on selected coals from the Parvadeh Area,Iran,were conducted using sedimentology,coal petrology,X-ray diffraction(XRD),scanning electron microscopy-energy dispersive X-ray analyzer(SEM-EDX),and proximate analysis.The sedi-mentary facies above and below the coal seams are mainly marine or marine-influenced facies,supporting that the coal-forming mires in the Parvadeh Area developed in a paralic environment,where the base level must be closely related to sea level.Sulfur contents are moderate to high and mark the influence of brackish/marine water,especially during transgres-sion after peat growth in a lower delta plain environment.The peat-forming mires extended on coastal/delta plain lobes.The lower delta plain/coastal plain coals are characterized by lateral continuity and substantial thickness,whereas few coals possibly representing the upper delta plain are thin and more discontinuous.The detrital nature and composition of the numerous partings and the overall high ash yield in the coal seams indicate an active tectonic area with high rates of creation of accommodation space over peat growth.Coal petrology and coal facies analysis exhibits a permanently high water table within a forest swamp and mostly rheotrophic conditions,sometimes with connection to the seawater.Accord-ing to paleoenvironmental reconstructions,it seems that coal layers may be thicker,with less sulfur(pyrite),but more clastic minerals and partings toward the western part of the area.Although these coal seams presently have low economic potential for the mining operation,partly due to great depth,this humic,high-volatile to medium-volatile bituminous coal may be suitable for exploration of coal bed methane resources.

Genesis of the low-permeability reservoir bed of upper Triassic Xujiahe Formation in Xinchang gas field,western Sichuan Depression

The genesis of a reservoir is a result of the combined action of deposition, diagenesis, tectonic reworking, and interaction of rock and fluid and the evolutionary environment. We discuss the genetic and evolution mechanism of a low-permeability reservoir bed of the Xujiahe Formation in the western Sichuan Depression on the basis of the study of diagenesis, diagenetic reservoir facies and the diagenetic evolution sequence. The research indicated that this reservoir bed can be divided into five types of diagenetic reservoir facies, namely strong dissolution, chlorite-lined intergranular pores, compaction and pressure solution, carbonate cementation and secondary quartz increase. There are, however, just two diagenetic reservoir facies which provide low-permeability reservoir beds, namely strong dissolution and chlorite-lined intergranular pores. We also analyzed their diagenetic evolution sequences and the origin of the low-permeability reservoir bed. Besides, it was also indicated that the composition and structure of sandstones, types of sedimentary microfacies, diagenesis history as well as the tectonic reworking in later periods are the main factors controlling the formation of the low-permeability reservoir bed. The above- mentioned factors establish the foundation for the forecasting the distribution of high quality reservoir beds.

Petrophysical and capillary pressure properties of the upper Triassic Xujiahe Formation tight gas sandstones in western Sichuan,China

The tight sandstones of the Upper Triassic Xujiahe Formation（T_3x） constitute important gas reservoirs in western Sichuan.The Xujiahe sandstones are characterized by low to very low porosity （av.5.22%and 3.62%） for the T_3x^4 and T_3x^2 sandstones,respectively）,extremely low permeability（av. 0.060 mD and 0.058 mD for the T_3x^4 and T_3x^2 sandstones,respectively）,strong heterogeneity,micronano pore throat,and poor pore throat sorting.As a result of complex pore structure and the occurrence of fractures,weak correlations exist between petrophysical properties and pore throat size,demonstrating that porosity or pore throat size alone does not serve as a good permeability predictor.Much improved correlations can be obtained between permeability and porosity when pore throat radii are incorporated. Correlations between porosity,permeability,and pore throat radii corresponding to different saturations of mercury were established,showing that the pore throat radius at 20%mercury saturation（R_（20）） is the best permeability predictor.Multivariate regression analysis and artificial neural network（ANN） methods were used to establish permeability prediction models and the unique characteristics of neural networks enable them to be more successful in predicting permeability than the multivariate regression model.In addition, four petrophysical rock types can be identified based on the distributions of R_（20）,each exhibiting distinct petrophysical properties and corresponding to different flow units.

Hydrocarbon Generation and Expulsion of the Upper Triassic T3x5Source Rocks in the Western Sichuan Depression: Assessment for Unconventional Natural Gas

Tight-sand gas in the Jurassic and shale gas within the fifth member of Xujiahe Formation （T3xs） in the Western Sichuan Basin （WSD） are currently regarded as the most prolific emerging unconventional gas plays in China. This study conducted a conventional evaluation of T3x5 source rocks in the WSD, and investigated their hydrocarbon generation and expulsion characteristics, including intensity, efficiency and amount. The results show that, the T3x5 source rocks are thick （generally 〉200 m）, and have a high total organic content （TOC）, ranging from 2.5 to 4.5 wt%. It is thus indivative of a great hydrocarbon generation potential when they underwent high thermal evolution （Ro〉1.2%） in the area. In addition, an improved method of hydrocarbon generation potential is applied, indicating that the source rocks reached a hydrocarbon expulsion threshold with vitrinite reflectance （Ro） reaching 1.06%. and that the comprehensive hydrocarbon expulsion efficiency is about 60%. The amount of hydrocarbon generation and expulsion from Tax5 source rocks is 3.14x10^10 t and 1.86x10^10 t, respectively, with a residual amount of 1.28x10^10t within them. Continuous-type tight-sand gas is predicted to have developed in the Jurassic in the Chengdu Sag of the WSD because of the good source-reservoir configuration; the Jurassic sandstone reservoirs are tight, and the gas expelled from the T3xs source rocks migrates for very short distances vertically and horizontally. The amount of gas accumulation in the Jurassic reservoirs derived from T3x5 source rocks is up to 9.3x10s t. Geological resources of shale gas are up to 1.05x10TM t. Small differences between the amounts calculated by the volumetric method and those obtained by hydrocarbon generation potential method may be due to other gas accumulations present within interbedded sands associated with gas shales.

Petrography and Geochemistry of the Upper Triassic Sandstones from the Western Ordos Basin, NW China: Provenance and Tectonic Implications

Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographic features show that the sandstones are characterized by low-medium compositional maturity and textural maturity.The CIA and CIW values reveal weak and moderate weathering history in the source area.The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature,while the provenance of the western and southwestern sediments were mainly from the Qinling-Qilian Orogenic Belt.The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc,which is closely related to the evolution of the QinlingQilian Orogenic Belt.However,the sandstones in the northwestern Ordos Basin show complex features,which may be resulted from a typical recycling process.Overall evidence from petrography,geochemistry and sedimentology,together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin,respectively,and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin,where a large,uniform sediment dispersal system developed during the Late Triassic.

Quantitative identification of relatively highlevel radioactive sandstone in the Upper Triassic Yanchang Formation of the Ordos Basin, China

Most relatively high-level radioactive sandstone(HRSS)reservoir has considerable oil(or gas)resource potential.HRSS is often wrongly identified due to its similar logging response characteristics as mudstone,which leads to the omission of effective reservoirs.In this paper,a quantitative identification method for HRSS is proposed after the analyzing of the response characteristics and relationship between spontaneous potential log and natural gamma-ray log in conventional sandstone and mudstone strata.Take the Upper Triassic Yanchang Formation in Ordos Basin as an example:the responses of spontaneous potential log and the responses of natural gamma-ray log are synchronized and positively correlated in conventional sandstone and mudstone strata,but they are not synchronized in HRSS.Quantitative identification of HRSS was realized based on this synchronization feature,and a"virtual compensation"of natural gamma-ray log was performed.At the same time,logging evaluation method about HRSS has been discussed.The final results shows that this identification method work effectively,and can reduce the misjudgment and omission of effective reservoirs.

Sedimentary system characteristics and depositional filling model of Upper Permian——Lower Triassic in South Yellow Sea Basin

In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.

The Late Triassic Sequence-Stratigraphic Framework of the Upper Yangtze Region,South China

In the transitional period between the Middle and the Late Triassic, the Indochina orogeny caused two tectonic events in South China：（1） the formation and uplift of the Qinling-Dabie orogenic belt along the northern margin of the South China Plate, due to its collision with the North China Plate; and 2） the development of a 1300-km-wide intra-continental orogen in the southeastern part of the South China Plate, which led to a northwestward movement of the foreland thrust-fold zone. These tectonic events resulted in the ending of the Yangtze Platform, and were a stable paleogeographic factor from the Eidacaran to the end of the Middle Triassic. This platform was characterized by the widespread development of shallow-water carbonates. After the end of the Yangtze Platform, the upper Yangtze foreland basin（or Sichuan foreland basin） was formed during the Late Triassic and became a accumulation site of fluvial deposits that are composed of related strata of the Xujiahe Formation. In western Sichuan Province, the Xujiahe Formation overlies the Maantang Formation shallow-water carbonate rocks of the Xiaotangzi Formation siliciclastic rocks（from shelf shales to littoral facies）. The sequence-stratigraphic framework of the Upper Triassic in the upper Yangtze foreland basin indicates a particular alluvial architecture, characterized by sequences composed of（1） successions of low-energy fluvial deposits of high-accommodation phases, including coal seams, and（2） high-energy fluvial deposits of low-accommodation phases, including amalgamated river-channel sandstones. The spatial distribution of these fluvial deposits belonging to the Xujiahe Formation and its relative strata is characterized by gradual thinning-out, overlapping, and pinching-out toward both the east and south. This sedimentary record therefore expresses a particular sequence-stratigraphic succession of fluvial deposits within the filling succession of the foreland basin. The sequence-stratigraphic framework for the Upper Triassic in the Upper Yangtze region provides a record of the end of the Yangtze Platform and the formation of the upper Yangtze foreland basin.

Sequence Boundary and Sea Level Changes in Western Margin of Upper Yangtze Platform during Permian and Triassic

During Permian and Triassic the western margin of Upper Yangtze platform had experienced an evolution from early rift stage to thermal subsidence and then to foreland basin. The tectonic transformations have resulted in five supersequences and nineteen third-order se- quences.During the rift stage,transgeressive carbonate platform was built up,while in the thermal subsidence stage,regressive carbonate platform with foreslope was formed.The closure of the Garze-Litang narrow oceanic basin resulted in the migration of foreland flexure toward the ctaton.The carbonate ramp in foreland basin setting was formed during the relative sea level rise which was caused by the change in basin volume.

准噶尔盆地上三叠统烃源岩评价与有效烃源灶分布预测

准噶尔盆地蕴含丰富的油气资源,已于多个层位取得油气勘探发现。然而,上三叠统厚层泥岩能否作为盆地有效烃源岩一直没有明确的定论,亟需开展全盆范围内上三叠统烃源岩评价工作并进行有效源灶分布预测,为该层系下一步勘探部署提供依据。为进一步明确准噶尔盆地上三叠统烃源岩时空分布特征及其生烃潜力,落实有效烃源灶分布范围内生烃强度,基于资料收集、剖面实测、钻孔岩屑观察采样和有机地球化学测试,利用多个地化参数开展了全盆范围上三叠统烃源岩有机质丰度、类型、成熟度评价,优选关键参数利用多层次模糊数学评价方法,圈定有效源灶范围。结果表明,上三叠统烃源岩分布范围广(基本全盆分布)、厚度大(可达350 m)、腹部埋深大(最大埋深11 km);烃源岩TOC含量为0.75%~8.3%,平均值为1.74%;S_(1)+S_(2)平均为2.78 mg/g,氯仿沥青“A”平均为0.354%;有机质类型以Ⅲ型和Ⅱ2型为主,陆源高等植物输入占优,相对较好的母质类型主要沿盆1井西凹陷—阜康凹陷方向分布,有机质成熟度处于低成熟—成熟热演化阶段,局部达高—过成熟阶段。按照中国煤系泥岩生烃潜力评价标准,上三叠统泥岩整体为一套差—中等质量烃源岩,烃源岩总体上具有一定的生烃潜力,特别是生气潜力。有效烃源灶分布于中央坳陷腹部的阜康凹陷西部—沙湾凹陷东部一带以及南缘冲断带的霍玛吐背斜带,有效烃源灶范围内烃源岩Ro大于1.3%,生油强度在50×10^(4)t/km^(2)以上,生气强度在3×10^(8)m^(3)/km^(2)以上。

孔隙型致密砂岩气藏产能控制因素

为了探究天然裂缝欠发育致密砂岩气藏的产能主控因素,以四川盆地北部元坝地区上三叠统须家河组二段和川中东峰场地区须家河组五段气藏为研究对象,分析了二者的地质特征、钻井工艺和储层改造技术,明确了孔隙型致密砂岩气藏天然气产能主控因素。研究结果表明:①古、今构造高部位是油气运聚成藏的指向区,天然气富集程度较高,气井高产概率较大,而构造低部位气井生产效果较差;②储层物性越好,成藏过程中天然气富集程度越高,且生产过程中天然气流动能力较强,故优质储层发育段越厚,气井产量越高;③裂缝欠发育致密砂岩气藏需通过储层改造才能获产,加大改造规模对优质储层发育的钻井增产效果明显;④由于致密砂岩储层局部发育,水平井能够钻遇更多的优质储层,故较直井而言,提产效果明显;⑤由于钻井液中的重晶石会对物性差—中等的储层造成污染,进而影响产量,故致密砂岩气藏钻井过程中需加强储层保护。结论认为:①孔隙型致密砂岩气藏产能主要受古、今构造位置,优质储层发育程度,储层改造规模和井型等因素控制;②优质烃源岩发育区、正向构造区和相对优质储层发育区的叠合部位可优先考虑部署井位。

川西新场构造带须二段浅水三角洲砂体结构特征及控制因素

川西新场构造带上三叠统须家河组二段砂体分布广泛、砂体类型多样且厚度差异较大,导致气藏层间隔层、层内夹层分布不均,储集层分布非均质性强烈,因此需对储集砂体沉积微相与砂体分布特征及砂体结构展开精细研究,为下一步储集层预测和气藏高效开发奠定基础。作者以Cross高分辨率层序地层学理论为指导,结合岩心、测(录)井、三维地震、分析测试等资料,系统阐明了川西新场构造带须二段砂体结构特征及其控制因素。研究结果表明:研究区整体处于浅水三角洲前缘亚相带,主要发育水下分流河道砂体,河口坝砂体次之,河道砂体侧向迁移频繁,垂向多期叠置、横向上广覆连片。不同位置水下分流河道特征差异大,结合其典型特征,将水下分流河道砂体进一步细分为削截型水下分流河道和完整型水下分流河道。总结出研究区共发育2大类9小类砂体垂向叠置样式和3种侧向接触样式。砂体结构特征和发育样式主要受基准面升降、河流能量控制。最终建立了川西新场构造带须二段沉积微相及砂体结构发育模式,这对浅水三角洲前缘的气藏勘探开发具有指导意义。

滇中禄劝地区三叠系舍资组矿产资源勘查新线索

通过1∶5万区域地质调查及典型剖面研究,在滇中禄劝地区三叠系舍资组底部识别出一套厚约10~100 m不等的含南红玛瑙砾岩层。南红玛瑙颜色主要呈橙红、大红色及紫红色等,少数呈柿子红,椭圆状、圆状,表皮干净,无杂质,总体成色较好,具有较好开发利用价值。物源对比和分析表明,舍资组南红玛瑙物源来自峨眉山玄武岩中的杏仁体。由于峨眉山玄武岩分布广泛,三叠系舍资组底部南红玛瑙的发现,为滇中地区寻找此类资源提供了新线索和找矿方向。此外,通过对舍资组泥页岩有机碳和镓等关键金属含量分析发现,有机碳含量相对较高(total organic carbon,TOC=2.83%~9.25%),有机质成熟度也较高,处于过成熟阶段;镓、铌(钽)-锂等关键金属也有较高程度富集,暗示该层位还具有良好的页岩气和关键金属找矿潜力。舍资组中植物化石显示,其沉积古气候是潮湿湿润的,有利于蕨类植物的生长繁盛,这为页岩气的形成提供了物源,也为关键金属的富集提供了有利条件。

资阳东峰场地区须家河组须五段气藏产能影响因素及稳产对策

针对四川盆地资阳东峰场地区上三叠统须家河组须五段气藏试采中表现出的单井天然气产能差异大、稳产效果差等问题,综合地质、动态监测、实验分析等资料,开展了产能主控因素及递减原因分析,提出了稳产对策。研究结果表明:①气井产能主要受井型和优质储层发育程度影响,水平井产能明显高于直井,优质储层越发育,气井产能越高;②气井稳产效果较差,稳产期平均为10个月,日产气量递减指数平均为0.0017,储层有效渗透率低、供气范围有限;③气井初期高配产带来大生产压差引发储层应力敏感伤害,地露压差小易析出凝析油造成储层反凝析伤害,使储层渗透率损失,导致气井产能迅速递减;④压裂砂回流使人工裂缝导流能力下降并在近井地带堆积造成砂堵,压裂液返排困难使气井积液甚至水淹,均会导致气井停产;⑤控压开采可有效降低储层渗透率的损伤,液氮助排、优化生产管柱有利于气井排液,延缓气井产能递减。该研究成果可以为类似地区致密砂岩气藏开发技术对策制订提供参考。

四川盆地须家河组坡折带发育特征及油气地质意义

前人针对断陷盆地坡折带开展了大量研究,但前陆盆地前渊向前缘隆起方向坡度较缓,大型构造欠发育,地形起伏小,坡折带研究较少。四川盆地晚三叠世须家河组四、五段沉积时期发育前陆盆地,学者们已关注到泸州—开江古隆起西侧川中—川西地区缓坡坡折带对沉积岩相的控制,但其他相关研究较少。通过对四川盆地地震反射剖面坡折带构造解释,结合区域地质已有成果,采用颗粒流数值模拟方法,厘清了川中—川西地区坡折带类型,以及坡折带与重力滑动构造之间的关系,分析了与重力滑动构造相关的新型油气圈闭特征。研究获得如下认识:(1)研究区发育断裂坡折带,以坡折带为界,东、西两侧各发育一套重力滑动形成的“前挤后拉”构造组合,构造变形强度弱于被动大陆边缘重力滑动构造;(2)研究区构造坡折带边缘断裂控制沉积相与砂体类型;(3)缓坡带重力滑动构造拉张区正断层下盘上升形成同沉积背斜发育的砂岩,与同期断陷内富有机质泥岩侧接,形成“旁生侧储”型油气藏;(4)陡坡带重力滑动形成的须五段同沉积背斜,被翼部泥岩以及滑动构造结束后沉积的泥岩所围限,形成源内砂体输导成藏;(5)与重力滑动构造相关的同沉积背斜油气藏是源内成藏新类型,研究区须五段可能存在平行坡折带NE向展布的此类油气藏。

致密砂岩微观特征及沉积古环境——以梓潼—秋林地区须三、二段为例

四川盆地西北部上三叠统须家河组纵向上发育多套致密砂砾岩气藏,具备多层系立体勘探的广阔前景。目前针对该区域须家河组沉积古环境及物源体系的认识还不够深入,导致勘探上有点无面,严重制约了下一步攻关方向,需要加强该区域沉积古环境的研究。通过显微薄片鉴定、全岩矿物X衍射、稀土微量元素分析,结合井、震资料,对主要层段须三段—须二段含气砂体岩石类型、矿物含量、物源条件、古气候、古盐度及古氧化还原条件进行系统分析和对比研究。研究结果表明:(1)须二上亚段以长石岩屑砂岩为主,石英及长石矿物发育,石英含量超过50%;(2)受龙门山碳酸盐物源供给影响,须三下亚段普遍含钙质,岩屑成分以碳酸盐岩为主,方解石与白云石矿物发育,石英含量低于50%;(3)须三下亚段砂体稀土元素特征较须二上亚段更为复杂,指示多物源特征,两者沉积时该区整体处于潮湿性干热古气候,沉积环境偏淡水氧化环境,但须三下沉积期比须二上沉积期气候更为潮湿、古盐度略高、氧化性也更强。研究成果对川西北部须家河组重点砂岩层段微观特征、沉积古环境及地层划分新方案具有一定参考意义。

东昆仑八宝山盆地上三叠统页岩气成藏地质条件分析

为探讨八宝山盆地上三叠统页岩气的成藏潜力,通过野外地质剖面测量、二维地震、调查井施工、录井、解析、样品采集及分析测试等工作,对研究区八宝山组的形成背景、泥页岩规模、生烃条件(TOC、Ro、有机质类型)、储集条件(矿物特征、储集空间、孔结构参数)、含气性、埋藏史和热演化史等进行研究。结果表明:①东昆仑八宝山盆地三叠纪以来经历了基底形成、断陷演化及隆升改造三个演化阶段,昆中、昆南断裂控制盆地沉积格局,在晚三叠世断陷期沉积滨浅湖、半深湖—深湖相的泥页岩夹砂岩、粉砂岩,受沉积相控制,自山前向盆地内泥页岩厚度逐渐增大,大部分地段累积厚度超过300 m,有效厚度在16.24~79.63 m之间,为八宝山组页岩气聚集成藏提供了物质基础;②井内714件样品的TOC含量分布在0.01%~49.14%,有机质类型以Ⅲ型为主,Ro在2.37%~3.45%,泥页岩有机质含量、热演化程度高,有机质类型好,生气条件优越;③八宝山组上段石英、黏土矿物含量平均为40.83%、46.06%;八宝山组下段石英、黏土矿物含量平均为39.62%、47.08%,与Barnett页岩、Marcellus页岩及四川盆地海相富有机质泥页岩相比,脆性矿物含量略低,黏土矿物含量稍高。八宝山组上、下段含气量平均为4.19 m^(3)/t、5.44 m^(3)/t,泥页岩中发育大量微裂缝、溶蚀孔隙、裂缝孔隙、粒间孔隙、有机质孔隙等,其比表面积、孔体积、孔径平均值分别为6.9403 m^②/g、0.0116 cm^(3)/g、8.5138 nm,有利于页岩气富集和吸附;④埋藏史、生烃史结果显示:八宝山盆地具有早期浅埋、中期深埋、晚期抬升的特点,上覆侏罗系羊曲组的硅质砾岩、碎屑岩及新生代沉积地层广泛分布,作为区域性盖层对页岩气藏起到了很好地封盖作用,综合研究认为八宝山盆地页岩气资源远景广阔。

Biostratigraphy of Triassic Marine Reptiles in Southwest Guizhou and Its Adjacent Area

This paper briefly reviews the Triassic marine reptile fossils in Guizhou Province, especially the fossils that have been recently found in the Guanling area. Based on three sections at Guanling and Xingyi, Guizhou Province and Luoping, Yunnan Province, four horizons with vertebrate fossils are recognized in the Middle and Upper Triassic of this area; They are from bottom to top: Member I and Member II of the Guanling Formation, and the Zhuganpo Member and the Wayao Member of the Falang Formation.