The Geochemical Characteristics of Stable Carbon and Oxygen Isotope and Analysis of Diagenetic Environment --A Case Study of Upper Permian Changxing Formation Dolostone in Northeast of Sichuan

四川盆地东北部上二叠统长兴组白云岩为重要的优质储层,近年来,长兴组白云岩成岩环境或成因问题成为研究者讨论的热点话题。在岩石学研究的基础上,运用稳定碳、氧同位素,对研究区长兴组白云岩进行综合研究表明,白云石化具有多期次的特点,按照成岩环境划分为蒸发环境下的准同生白云岩和埋藏条件下的早、中、晚期成岩白云岩。并划分为早、中、晚成岩阶段,结合碳、氧同位素分析结果进一步表明晚成岩阶段白云岩是构造热液白云石化的结果。

Geochemical characteristics of the Permian Changxing Formation reef dolomites,northeastern Sichuan Basin,China

The recent discovery of deep and ultra-deep gas reservoirs in the Permian Changxing Formation reefs, northeastern Sichuan Basin is a significant development in marine carbonate oil ＆ gas exploration in China. Reef dolomites and their origins have been major research topics for sedimentologists and oil ＆ gas geologists. The petrography, trace element and isotope geochemistry of the reef dolomites indicated that the dolomites are characterized by low Sr and Mn contents, relatively low Fe contents, very similar δ13C and 6180 values and very different 87Sr/86Sr ratios. Although the calculated results of the fluid mixing suggested that a mixture with 85%-95% meteoric water and 50/o- 15% seawater seemed to be the dolomitizing fluids of the reef dolomites, the low Mn contents, relatively low Fe contents, high δ13c values and high homogenization temperatures of the dolomites did not support that there were large proportions of meteoric water in the dolomitization process, and the 87Sr/86Sr ratios which were close to coeval seawater also did not support the possibility of the mixture of deep-burial circulated fluids from clastic rocks. High temperature deep-burial circulated seawater with low Mn and Fe contents, high Sr content and high δ13C values from the dissolution of widely distributed Triassic evaporites during the burial diagenetic processes （including dehydration of water-bearing evaporites） could have been the dolomitizing fluids of the reef dolomites.

Sedimentary architecture and distribution of intra-platform shoal in sequence framework of Permian Changxing Formation in central Sichuan Basin,SW China

Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.

Prestack inversion identification of organic reef gas reservoirs of Permian Changxing Formation in Damaoping area, Sichuan Basin, SW China

Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surrounding rock, it is difficult to identify and predict the reservoirs and fluid properties by conventional post-stack inversion. Through correlation analysis of core test data and logging P-S wave velocity, this work proposed a formula to calculate the shear wave velocity in different porosity ranges, and solved the issue that some wells in the study area have no S-wave data. AVO forward analysis reveals that formation porosity is the main factor affecting the variation of AVO type, the change of water saturation cannot affect the AVO type, but it has an effect on the change range of AVO. Through cross-plotting analysis of elastic parameters, it is found that fluid factor is a parameter sensitive to gas-bearing property of organic reef reservoir in the study area. By comparing results of post-stack impedance inversion, post-stack high frequency attenuation property, pre-stack simultaneous inversion and AVO anomaly analysis of angle gathers, it is found that the gas-bearing prediction of organic reef reservoirs by using fluid factor derived from simultaneous pre-stack inversion had the highest coincidence rate with actual drilling data. At last, according to the characteristics of fluid factor distribution, the favorable gas-bearing area of the organic reef reservoir in Changxing Formation was predicted, and the organic reef trap at the top of Changxing Formation in Block A of Damaoping area was sorted out as the next exploration target.

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.

Facies Analysis and Depositional Environment of Upper Permian Rocks in Darin Section, East-Central Iran

Deposits of Permian rocks in Kalmard Block are recognized with Khan Group, showing various characteristics in different outcrops. This group is made up of three informal formations, namely Chili, Sartakht and Hermez. Upper Permian deposits (Hermez Formation) are composed chiefly of lateritic and carbonate rocks. This formation is composed of 65.5 m lateritic soils, lateritic sandstone, limestone, dolomite and dolomitic limestone in the Darin section. This formation unconformably overlies middle Permian siliciclastic and evaporite deposits (Sartakht Formation), where as it is depicted underlying an erosional unconformity above lateritic deposits of lower Triassic (Sorkh Shale Formation). According to lithologic and microscopic investigations, the deposits of Hermez Formation can be divided into 1 siliciclastic petrofacies and 14 carbonate microfacies. Field observations, along with microscopic examinations, have resulted in identifying tidal flat, lagoon, shoal and open marine environments in the rocks of the studied formation. Vertical changes of microfacies and depth variation curve point to the high thickness of the microfacies of lagoon, tidal flat and shoal environments and low thickness of open marine microfacies. Hermez Formation rocks in Darin section are deposited in a low-angle homoclinal ramp, mostly in the inner ramp, located in the southern Paleo-Tethys Ocean.

Lithofacies palaeogeography of the Upper Permian Changxing Stage in the Middle and Upper Yangtze Region,China

Based on the petrological study,according to single factor analysis and multifactor comprehensive mapping method,the quantitative lithofacies palaeogeography of the Upper Permian Changxing Stage of the Middle and Upper Yangtze Region was studied.The Changxing Stage in the Middle and Upper Yangtze Region is mainly composed of carbonate rocks;in addition,clastic and siliceous rocks occur with rare coals and pyroclastic rocks.Lithofacies can be divided into five types,including clastic rock assemblage,clastic rock-limestone assemblage,limestone assemblage,limestone-siliceous rock assemblage,and siliceous rock-clastic rock assemblage.Four fundamental ecological types and five fossil assemblages were recognized in the Changxing Stage.On the basis of the petrological and palaeoecological study,eight single factors were chosen including thickness,content of marine rocks,content of shallow water carbonate rocks,content of bioclasts with limemud matrix,content of bioclasts with sparry cement,distribution of reefs,content of thin bedded siliceous rocks and content of deep water sedimentary rocks.And eight single factor maps and one lithofacies paleogeographic map of the Changxing Stage were compiled.Paleoenvironments from west to east include an erosional area,fluvial plain,clastic platform,carbonate platform and reefs that developed there,slope and basin,low energy organic banks,and high energy organic banks.Sedimentary environments have an obvious control on the development of the source rocks,and the excellent source rocks are developed in the Dalong Formation.Changxing Stage reservoirs should be dominated by the reef and platform surrounding the GuangyuanLiangping Basin rim area,and is the most favorable exploration area of the reef petroleum reservoirs of the Changxing Formation.

Discovery of the Upper Permian series in Cuoqin Basin,Xizang (Tibet) and its geological significance

During the field work,one assumption has been made according to the lithologic,especially the paleotogic characteristics observed. The assumption is that the Upper Permian series should exist in Aduogabu which is in Xiadong Town, Gaize County, Tibet. This assumption was verified by the results of paleontologic identification. Accordingly it can be concluded

Ufadendron elongatum sp. nov., an Angaran Lycopsid from the Upper Permian of Inner Mongolia, China

A new species Ufadendron elongatum sp.nov.,attributed to the family Tomiodendraceae Naugolnykh,is represented by two well-preserved stems in the collection under study.This new species was recently discovered from the Upper Permian Linxi Formation in the Jalaid locality,the Inner Mongolia Autonomous region,China.The genus Ufadendron is characterized as having the long fusiform leaf cushions,with small and rounded leaf scar containing a central point-like scar which is situated at the upper part of leaf cushion;the infrafoliar bladder of fusiform shape positioned in the middle part of leaf cushion;the wings and heel well-developed in the lateral parts and the lower part of leaf cushion,respectively.The new species is different from the type species U.ufaense(Naugolnykh 2014)collected from the Lower Permian of the Cis-Urals,western limits of Angaraland,in the elongated leaf cushion and in the well-pronounced heel.It should be noted,that a vascular bundle(conductive strand)occupied the middle part of the central point-like scar.So far,only 5 genera of Angaran elements among lycopsids have been discovered in the region geographically belonging to Angaran Realm(Phytogeoprovince)in China.The new species U.elongatum not only enlarges our knowledge on the taxonomy of Tomiodendraceae lycopsids,and also provides an opportunity to understand the difference between Angaran and Cathaysian floras in paleoclimatic context.

Characteristics and formation mechanism of Changxing Formation-Feixianguan Formation reef-shoal reservoirs in Yuanba Gasfield

Taking advantage of the successful experience in exploring and discovering the Puguang Gasfield,and targeting the Changxing Formation-Feixianguan Formation organic reef and shoal lithological trap,SINOPEC drilled Well Yuanba 1 in the Bazhong area in Northeast Sichuan in 2006,and discovered the Yuanba Gasfield with a high-production commercial gas flow of 503×10^(3) m^(3)/d.As a normal-pressured lithological gas reservoir with high H_(2)S content,Yuanba Gasfield is characterized by weak tectonic deformation and deep burial,with an average depth of 6,600 m in the central part of the gas reservoir,and is the deepest marine gas field in the Sichuan Basin.Yuanba Gasfield is dominated by large-scale reef-shoal reservoirs of Changxing Formation.The formation of the reservoirs was primarily controlled by early meteoric freshwater dissolution and dolomitization,and less affected by deep-burial dissolution and tectonic movement.A comparative analysis was made on the characteristics of deep reef-shoal reservoirs in the Yuanba and Puguang gas fields so as to explore their formation mechanisms.It is concluded that the reservoir size and early pore development was controlled by early depositional-diagenetic environment.Fracture formation and dissolution were controlled by structure-fluid coupling,pore reworking and preservation is determined by fluid-rock interaction.

四川盆地东南部南川地区煤层气地质特征及富集主控因素

四川盆地东南部南川地区上二叠统龙潭组深层煤层气勘探取得重要战略突破,展现出该区煤层气良好的勘探潜力。为揭示其富集主控地质因素,利用钻井、岩心、测井及实验分析等资料,从龙潭组煤层分布、煤岩煤质、物性、含气性以及可压裂性特征等方面入手,开展了煤层气地质特征与富集主控地质因素研究。研究表明:(1)龙潭组主力煤层具有分布稳定(厚度2.8~5.7 m)、煤体结构好(主要为原生结构煤)、镜质组含量高(平均含量79.7%)、热演化程度较高(R_(o)平均为1.9%)和灰分产率较低(平均14.3%)的特点,具备形成煤层气藏的基本条件;(2)煤储层为孔隙—裂隙型储层,微孔占比78%,其比表面积占比达99.6%,有利于煤层气的吸附及压裂后渗流;(3)煤层总含气量为14.0~46.7 m^(3)/t,游离气占比为39%~44%,具有“高含气、富含游离气、过饱和”及含气量随埋深增加而增大的特征;(4)研究区地应力适中(35~60 MPa),两向水平应力差异系数小(<0.1),顶底板条件好,可形成良好的应力隔挡,有利于压裂改造;(5)南川地区煤层气富集主控地质因素为沉积环境控制含煤建造、演化程度控制生烃强度、保存条件控制富集程度。

川东北地区二叠系吴家坪组二段页岩储层特征及有利区分布

四川盆地上二叠统吴家坪组海相页岩是页岩气勘探开发的热点层系。通过X射线衍射、薄片鉴定、扫描电镜、有机地球化学、低温氮气吸附等分析,对川东北地区二叠系吴家坪组二段海相页岩的沉积相展布、储层及烃源岩特征进行了分析,明确了储层发育的主控因素,并对储层发育有利区进行了预测。研究结果表明:①川东北地区吴二段的沉积受海平面上升和裂陷发育的影响,主要为深水陆棚相,在达州—开江—万州—忠县一带沿北西—南东方向呈连通条带状展布。②研究区吴二段页岩储层中矿物组成复杂,脆性矿物含量较高,平均质量分数为67.9%;与四川盆地志留系龙马溪组页岩相似,研究区的石英具有生物成因特征而呈絮凝状,草莓状黄铁矿粒径均较小(小于6.0μm),指示沉积水体为还原环境,有利于有机质的富集;页岩储层平均孔隙度为4.11%,孔隙类型包括有机质孔隙、粒内孔隙、粒间孔隙及微裂缝,孔隙结构以狭缝孔为主,中孔对孔体积的贡献率最大。③研究区吴二段烃源岩具有高TOC含量、高成熟度特征,TOC平均值为4.80%,R_(o)平均值为2.53%,达到过成熟阶段,干酪根类型主要为Ⅱ型,具有良好的生气潜力,基本达到Ⅰ类页岩气储层标准。④研究区吴二段储层主要受控于沉积环境和成岩改造作用,深水陆棚沉积环境有利于页岩储层的形成,石英的抗压保孔作用和有机质生烃作用是页岩储层形成的关键,石英含量、TOC含量和孔隙度均呈正相关关系;开江—梁平、万州地区为吴二段有利页岩储层分布区。

Distribution and gas-bearing properties of Permian igneous rocks in Sichuan Basin, SW China

Based on the analysis of outcrop, seismic, logging and drilling data, combined with exploration practice, the characteristics,distribution, reservoir performance and gas-bearing properties of Permian igneous rocks in Sichuan Basin are studied. The study shows that central volcanic eruptive facies are developed in Sichuan Basin, and their lithological assemblages and distribution characteristics show obvious differences. The igneous rocks are mainly distributed in three regions: the southwestern part of the basin has dominantly largescale overflow facies basalts; the central and western part of the basin, Jianyang-Santai area, develop intrusive rocks, volcanic lavas(basalts)and pyroclastic rocks; and the eastern part of Sichuan, Dazhou-Liangping area, only develop diabase and basalts. Five aspects of understandings are achieved:(1) The Upper Permian igneous rocks can be divided into intrusive rocks and extrusive rocks, with the extrusive rocks as the main body. The chemical compositions of the extrusive rocks are characterized by both alkaline basalt and tholeiitic basalt, and belong to the subalkaline type of transitional basalt magma eruption.(2) There are obvious rhythmic structures vertically among overflow facies basalt, and the single rhythmic layer consists of, from bottom up, pyroclastic rocks(undeveloped), gray and dark gray porphyritic basalts(unstable), dark gray and purple microcrystalline-cryptocrystalline basalts, dark greyish green porous and amygdaloid basalts; the central volcanic eruption shows the rhythm and the vertical sequence of volcanic clastic rocks(agglomerates and breccias), volcanic lava, tuffaceous lava from bottom to top.(3) The pore types of basalt and pyroclastic rocks are diverse, mainly dissolution pore and de-vitrification micropore, but their physical properties are different. Basalt is characterized by ultra-low pore permeability, small reservoir thickness, and reservoirs are distributed in the upper and middle parts of the cycle, with poor lateral comparability. Volcanic clastic rocks are medium to high porous reservoirs(Well YT1: porosity: 8.66%?16.48%, average 13.76%) with large thickness and good reservoir quality.(4) Natural gas in basalts in southwestern basin mainly comes from Middle Permian, and natural gas in volcanic clastic rocks in central and western basin comes from Cambrian Qiongzhusi Formation.(5) Analysis of igneous reservoir-forming conditions in different areas shows that there are relatively insufficient gas sources and great differences in preservation conditions in southwestern basin.Reservoirs are poorly developed and gas-bearing is complex. The Jianyang-Santai area in the central and western part of Sichuan Basin has abundant hydrocarbon sources, developed reservoir, favorable preservation conditions and favorable gas geological conditions, and it is a favorable area for gas exploration.

准噶尔盆地沙湾凹陷二叠系上乌尔禾组流体相态及油气藏类型

准噶尔盆地腹部地区沙湾凹陷超深层蕴含丰富的油气资源。根据烃源岩热演化模拟实验分析了沙湾凹陷二叠系上乌尔禾组烃源岩生烃产物类型,结合地层流体高温高压物性实验数据,运用相图判别法和经验参数法对沙湾凹陷征10井地层流体相态进行深入研究。研究结果表明:①沙湾凹陷征10井上乌尔禾组油气主要来自于下乌尔禾组泥质烃源岩,其有机质类型为Ⅱ1型,镜质体反射率(Ro)为1.05%~1.46%,岩石热解峰温(T_(max))为433~446℃,处于成熟—高成熟演化阶段,目前处于生轻质油阶段。②上乌尔禾组地层流体成分表现为凝析气藏的流体组成,地层温度为166.0℃,介于临界温度和临界凝析温度之间,地层压力为155MPa,远高于露点压力,地-露压差大,表明地层条件下流体呈凝析气相特征,但地下油气相态与地表采出流体相态具有一定差异。相图判别法和经验参数法烃类流体相态分析结果均显示,征10井上乌尔禾组气藏为含大油环的凝析气藏。③沙湾凹陷上乌尔禾组具有优越的成藏条件,紧邻下乌尔禾组烃源岩,油气近源垂向输导,向局部隆起区运聚,巨厚的三叠系及上乌尔禾组中上部区域盖层起到重要的封盖作用,最终在局部隆起区形成岩性-构造凝析气藏。

筠连地区上二叠统乐平组层序地层及沉积相研究

四川南部筠连地区乐平组煤层气资源储量大,勘探程度总体较低,制约了煤及煤系气资源的开采。煤层聚集、砂岩储层展布受控于沉积相及层序地层格架控制。为探究研究区内煤层发育特征及煤层聚集的沉积控因,以钻井和岩心资料为基础,利用层序地层学原理,识别出区内乐平组发育的Ⅲ级层序界面并划分层序,构建层序地层格架;厘清研究区含煤地层名称;利用岩相标志及测井响应特征进行地层对比、单井沉积相划分及连井沉积相对比,明确沉积相在各层序内的发育特征。结果表明,研究区乐平组共存在四个层序界面,依据四个层序界面划分出三个Ⅲ级层序。以测井响应特征为主体,共识别出两类沉积相,五类沉积亚相及九类沉积微相。第一层序(SQ1)和第二层序(SQ2)主要发育河流相,第三层序(SQ3)发育潮坪相。在剖面上,整体表现为由河流相至潮坪相的演化特征;自西向东体现为河流-潮坪-潟湖相的演化趋势。

川东红星地区中上二叠统页岩气勘探成果及方向展望

基于构造、岩心、测井等资料,采用电镜扫描、低温N_(2)吸附实验、高压压汞实验、盆地模拟等手段,系统分析了川东红星地区中上二叠统页岩的沉积演化、储层特征及页岩气富集模式,明确了勘探有利区,总结了勘探成果及意义。研究结果表明:(1)红星地区中上二叠统的沉积演化表现为:栖霞组—茅口组三段为开阔台地相;茅四段底部为台地-陆棚相,相带变化快,茅四段顶部为斜坡-陆棚相,地层被剥蚀、南厚北薄;吴家坪组一段(吴一段)底部为海陆过渡滨岸沼泽-潟湖相,吴一段顶部为台地-斜坡-陆棚相,斜坡-陆棚相带分布范围小、相变快;吴二段为斜坡-陆棚相沉积,从早至晚依次受控于古气候、火山活动和古气候、火山活动,沉积中—晚期古生产力较高,TOC均值大于8.00%。(2)研究区茅四段及吴二段陆棚相区发育2套优质页岩,具有“高有机碳-高灰质”的特征,富有机质页岩厚度分别为19 m和25 m,孔隙类型以有机孔为主,结构以微孔和介孔为主;富碳凝灰岩薄夹层混合质页岩岩相、高碳凝灰岩薄夹层硅质页岩为优质岩相,孔隙度分别为6.27%和6.43%,TOC值分别为10.11%和9.35%,含气饱和度分别为92.59%和91.81%,脆性指数分别为55.24%和61.19%,是地质和工程的双“甜点”段。(3)研究区二叠系广泛发育的层状藻为主要有机质来源;在侏罗纪主排烃期,其构造稳定、二叠系烃源岩排烃较少,中侏罗纪—早白垩纪早期为主生气期,构造活动较弱,页岩气的保存条件好,现今已完成生气过程,处于成熟—过成熟阶段,Ro值约2.1%,勘探潜力巨大。(4)建南、龙驹坝、三星区块为有利勘探区,其中建南区块潜力最大;茅四段(3)小层及吴二段(3)小层为优质层系的靶窗层段。

准噶尔盆地东道海子凹陷二叠系平地泉组烃源岩特征及热演化史模拟

基于钻井、录井、测井及烃源岩分析测试等资料,对准噶尔盆地东道海子凹陷二叠系平地泉组烃源岩的生烃潜力和热演化史进行了系统研究。研究结果表明:(1)准噶尔盆地东道海子凹陷二叠系平地泉组烃源岩主要为深灰色、灰黑色泥岩,颜色深且厚度普遍较大,自东北部斜坡区向凹陷中部厚度逐渐增大,并向西部莫索湾凸起逐渐减小,最大泥岩厚度可达536 m。(2)研究区平地泉组烃源岩有机质丰度综合评价为中等—极好,纵向上以平一段有机质丰度最高,平面上以凹陷东北部滴南7井区和滴南19井区最高;平地泉组有机质类型主要为Ⅱ_(2)—Ⅲ型,少部分为Ⅱ_(1)型,纵向上以平二段有机质类型最好,平面上凹陷区烃源岩有机质类型主要为Ⅱ_(1)—Ⅱ_(2)型。(3)热演化史模拟结果显示,凹陷区和斜坡区烃源岩分别在晚三叠世和晚侏罗世达到生烃高峰,现今分别处于高成熟阶段和成熟阶段。(4)研究区发育“下生上储”和“自生自储”2类油气藏,其中平地泉组烃源岩与上乌尔禾组储集层形成“下生上储”油气藏,平二段和平一段的优质烃源岩与湖盆边缘的小型扇三角洲沉积在平地泉组内部形成“自生自储”油气藏,二者油气勘探潜力均较大。

银额盆地苏红图坳陷MSD1井二叠系地层厘定及油气地质意义

长久以来,由于银额盆地覆盖区二叠系地层特征认识不清,致使盆地内钻井揭示的油气产层地质时代存在争议。本次研究利用银额盆地苏红图坳陷MSD1井下部井段岩心样品开展了孢粉学、矿物学、锆石年代学等研究工作,结合盆地内钻井、地震测线及地表露头资料开展地层对比,取得了以下认识:(1)苏红图坳陷MSD1井2669.00~2726.00 m井段内发现的Florinites,Vesicaspora,Striatoabieites,Vittatina和Hamiapollenites等孢粉分子,且碎屑岩薄片显微镜下见腕足、海百合、苔藓虫等零散生物碎屑分布,均指示该段地层为上二叠统哈尔苏海组,时代为二叠纪晚期。(2)结合钻井时井深标定及地震层位追踪,明确银额盆地二叠系在盆地覆盖区广泛分布,二叠系地震反射呈现弱反射–空白反射、中–弱振幅、层内连续性差、底界偶见强振幅连续界线的特征,反映二叠系沉积后经历了多期构造改造作用。(3)盆地内多口钻井发现白垩系、二叠系的两套含油气系统,钻井烃源岩地球化学特征显示银额盆地二叠系具有丰富的油气勘探潜力。综合研究认为,银额盆地二叠系原型盆地分布范围广、油气资源潜力丰富,后期构造改造分区性强,局部地区构造破坏严重,MSD1井二叠系古生物地层学、锆石年代学、岩石矿物学及地球物理学地层特征的发现,实现了盆地露头区与覆盖区二叠系特征对比统一,明确了银额盆地二叠系的油气勘探前景。

准噶尔盆地阜康凹陷二叠系上乌尔禾组砂砾岩储层特征及发育模式

准噶尔盆地阜康凹陷二叠系上乌尔禾组砂砾岩具有较大的油气勘探潜力,目前存在的砂砾岩储层特征以及成储机制不清晰等问题,严重制约了对该类储层的勘探。利用显微薄片、扫描电镜、X射线衍射等对准噶尔盆地阜康凹陷上乌尔禾组砂砾岩储层特征、主控因素以及成储模式进行了系统研究。结果表明:上乌尔禾组砂砾岩具有“双填隙物”特征,砾石间主要被较粗的砂质组分填隙,胶结作用主要发生于砂质组分之间;砂砾岩孔隙度低,砾石中基本不发育孔隙,砂质填隙物中孔隙较发育,储集空间主要为晶间孔和次生溶孔;与储层形成有关的成岩演化现象主要发生在砾石之间的粗填隙物砂质组分中,主要为铝硅酸盐矿物的溶蚀作用,形成较多的溶蚀孔隙;河口坝、水下分流河道等高能沉积微相中储层更发育,储集空间主要与长石溶蚀有关,裂缝、不整合面是酸性流体运移的主要通道;早成岩期酸性流体主要为沿不整合面下渗的大气水,尤其是靠近北三台凸起的区域大气淡水溶蚀更为显著,中成岩期主要为有机酸溶蚀;砂砾岩中发育大气酸溶蚀型、有机酸溶蚀型和双源酸叠加溶蚀型等3类储层,不同类型储层分布决定了阜康凹陷上乌尔禾组砂砾岩油气藏的勘探方向,斜坡区、凹陷区的砂砾岩+断裂发育叠合区是阜康凹陷上乌尔禾组砂砾岩油气勘探的重点方向。

玛湖凹陷西南地区二叠系油气藏相态类型及凝析油气地球化学特征

利用PVT相态模拟软件恢复了玛湖凹陷西南地区二叠系油气藏原始储层流体组分,综合经验统计法与相图判别法对已发现油气藏的相态类型进行了判识,通过油气地球化学分析方法,明确了不同相态类型油气的来源及成因。研究结果表明:①玛湖凹陷西南地区二叠系油气藏主要分布在风城组和上乌尔禾组,油气藏的相态类型多样,以黑油油藏为主,挥发性油藏和凝析气藏(带油环的凝析气藏和近临界态凝析气藏)次之,凝析气藏主要发育在风城组,储层流体组分以甲烷为主,C7+烃类含量较少。②研究区二叠系不同相态原油的母质类型为偏腐泥型,均为风城组烃源岩成熟阶段的产物,凝析油的成熟度略高于其他相态类型原油,比其他相态类型原油物性更好,具有低黏度、低凝固点和低含蜡量的特点。③研究区二叠系天然气的组分以烃类气为主,其中甲烷的平均摩尔分数为86.21%,非烃类气含量低,成熟度差异较大,R_(o)为0.52%~2.39%;主要为风城组腐泥型烃源岩的产物;上乌尔禾组油气藏中天然气成熟度更高,平均R_(o)值为1.99%,风城组油气藏和凝析气藏中的天然气成熟度较低,平均R_(o)值分别为0.71%和0.85%。④受风城组烃源岩的热演化程度和储层物性影响,研究区二叠系发育2套含油气系统,分别为风城组的源内自生自储型油气藏和上乌尔禾组的源外下生上储型油气藏。