松辽盆地松科1井晚白垩世沉积时期古湖泊生产力

通过对松科1井不同层位泥岩样品的地球化学分析,利用有机碳法计算古海洋生产力公式定量恢复了白垩纪时期松辽古湖泊生产力,探讨了湖泊演化过程中生物发育、水体环境的变化及生产力与优质烃源岩关系.结果显示:青山口组一段和嫩江组一段时期生产力最高,最大值达到3 000g/(m2·a),生物标志化合物指标反映了该时期以藻类为主要贡献,水体具有盐度分层,湖底为厌氧环境,可能与海侵作用有关,此时湖泊为超富营养或富营养湖,反映出高生产力与湖泊中藻类勃发、水体分层、湖底厌氧等条件有关;青二、三段早期继承了青一段时期湖泊特点,具有相对较高的生产力,为中至富养湖;之后生产力逐渐下降,到晚期时生产力又有增大,为中养湖.姚家组一段沉积时期湖泊生产力平均为365 g/(m2·a),为中养湖;姚家组二、三段沉积早期和晚期时生产力均较低,一般低于100 g/(m2·a),属贫养湖;而在沉积中期生产力有明显增大,为中养湖.生产力、泥岩中生物标志物的变化反映了湖泊在白垩纪沉积时期生物发育、水体环境出现振荡变化.超养湖和富养湖的高生产力是形成优质源岩的基础.     

松辽盆地北部青一段油页岩地球化学特征及其记录的古湖泊学信息

油页岩地球化学特征及其记录的古湖泊学信息是揭示油页岩成矿富集规律的关键佐证。根据含油率、TOC、岩石热解、元素分析、生物标志化合物检测及有机显微组分分析,精细刻画了松辽盆地北部ZY1井青一段油页岩的地球化学特征,并分析了其记录的古湖泊学信息,探讨了古湖泊对油页岩有机质富集的控制作用。结果表明：青一段发育8层中等偏好品质的油页岩,下部为高品质油页岩富集层段;油页岩的含油率和TOC质量分数相关性极好,处于未熟—低成熟度演化阶段,生烃潜力大;油页岩中含丰富的萜类和甾类化合物,有机质类型主要为Ⅰ型,有机质来源主要为层状藻占优势的湖泊水生生物。地球化学参数指示,青一段下部古湖泊生产力呈现3个低→高的旋回,对应的古湖泊水体盐度呈现为3个半咸水-咸水旋回、古湖泊水体氧化还原性表现为还原-强还原-还原的厌氧环境,其中旋回Ⅱ后期湖泊生产力最高,对应的水体盐度最高、还原性最强。表明湖泊富营养化造成的高湖泊生产力是青一段高品质油页岩有机质富集的物质基础,盐度分层控制下强还原的湖底环境是高品质油页岩有机质富集的良好保存条件。     

中国湖相碳酸盐岩碳氧同位素时空特征及其古湖泊学意义

湖相碳酸盐岩是一种分布极其广泛的陆相碳酸盐岩。中国湖相碳酸盐岩沉积始于二叠纪—三叠纪,经侏罗纪—白垩纪发展,鼎盛于古近纪,具有沉积时间跨度长、分布面积广的特征。碳酸盐岩发育方式多样,常以多个单层、薄夹层状、互层状、韵律沉积为主,也见以结核状或钙质微体化石等薄层赋存于泥岩、页岩等细粒碎屑岩中。湖相碳酸盐岩δ¹³C值介于-10.0×10^-3~+10.0×10^-3之间,多数为-5.0×10^-3~+5.0×10^-3,正负值均有。二叠系—三叠系δ¹³C发生负偏,侏罗系—白垩系先正向漂移随后负偏,古近系—新近系再次正偏,达最大值约+5.0×10^-3。氧同位素δ¹⁸O值介于-20.0×10^-3~+2.0×10^-3之间,多数为-15.0×10^-3~-0.0×10^-3,几乎全部为负值。二叠系—三叠系、侏罗系—白垩系碳酸盐岩δ¹⁸O值在-15.0×10^-3~-3.0×10^-3之间变化,古近系—新近系δ¹⁸O值明显正偏移,多数位于-10.0×10^-3~0.0×10^-3。中国湖相碳酸盐岩碳氧同位素相关性分析表明,δ¹³C与δ¹⁸O密切相关,且δ¹³C值多正值或轻微负值,指示湖泊为封闭型咸水—半咸水环境;δ¹³C和δ¹⁸O不相关,δ¹³C值为负值,指示湖泊为开放型淡水环境。     

辽西早白垩世义县组砖城子层湖相碳酸盐岩地球化学特征及古湖泊学沉积意义

辽西义县盆地早白垩世义县组陆相湖盆沉积中常发育多个薄层碳酸盐岩沉积层,碳酸盐岩地球化学的研究对揭示湖盆沉积古环境具有重要理论意义。义县组砖城子层英窝山剖面湖相碳酸盐岩分析结果显示,岩石δ¹³C值为-3.44×10^-3~0.27×10^-3,均值为-1.21×10^-3;δ¹⁸O值为-15.73×10^-3~-9.93×10^-3,均值为-10.88×10^-3。盐度Z值变化范围114.78~122.39。碳酸盐岩主量元素分析表明,w（CaO+MgO+LOI）=53.38%~97.04%,均值71.15%;陆源组分w（Al₂O₃+SiO₂+Fe₂O₃）=2.19%~44.87%,均值为27.77%;x（Mg）/x（Ca）摩尔比介于0.92~1.01。碳酸盐岩微量元素地球化学提供了古湖泊学的古盐度、氧化还原和古气候证据。w（Sr）=110.4×10^-6~1360.2×10^-6,w（Ga）=0.152×10^-6~14.13×10^-6,w（Sr）/w（Ba）=0.34~131.49（多数>1）,指示沉积湖泊水体为咸水环境;氧化-还原指标w（V）/w（V+Ni）＝0.51~0.83,w（V）/w（Cr）＝1.59~8.28（多数>2.0）,w（U）/w（Th）=0.39~10.24,且变化范围较大,指示为半封闭—封闭的缺氧还原强分层水体沉积环境;w（Sr）/w（Cu）=54.94~1260.71,均值为213.79,反映炎热干旱气候类型。义县组砖城子层沉积期湖泊为干旱古气候背景下的半咸水—咸水、缺氧还原强分层的半封闭—封闭型。     

四川盆地下侏罗统自流井组湖相碳酸盐岩的碳、氧同位素特征及其古湖泊学意义

四川盆地侏罗纪的湖相碳酸盐岩主要分布于早侏罗世自流井组地层之中。在对四川自贡、重庆合川自流井组上部大安寨段中的湖相碳酸盐岩的碳、氧同位素进行分析后,根据其组成特征及其相关性,探讨其碳、氧同位素的古湖泊学意义。两条剖面上碳酸盐岩的碳、氧同位素在组成上存在一定的差异,自贡贡井—高硐桥剖面上,样品的碳、氧同位素均为负值,δ13C值在-4.49‰~-0.85‰之间,1δ8O值-9.14‰~-6.75‰之间,两者具有一定的相关性(γ=0.62);合川炭坝剖面上,样品的碳同位素正负均有,氧同位素均为负值,δ18O值在-8.52‰~-4.56‰之间,δ13C值在-3.46‰~1.62‰之间,两者也具有一定的相关性(γ=0.64)。通过与现代湖泊碳酸盐碳、氧同位素特征的比较,认为四川盆地早侏罗世自贡地区的湖泊为开放型的淡水湖泊,而合川地区为具有一定封闭性的微咸水湖泊。     

东营凹陷沙河街组湖相碳酸盐岩碳氧同位素组分及其古湖泊学意义

湖相碳酸盐岩的碳、氧稳定同位素分析能提供重要的环境信息。山东东营凹陷沙河街组湖相碳酸盐岩主要分布在沙一段和沙四段。对47个碳酸盐岩样品碳、氧同位素组分的分析表明:沙一段、沙四中和沙四上亚段下部沉积时期东营湖均是程度不同的封闭型湖泊。古盐度和蒸发／降雨:沙四中亚段和沙四上亚段下部沉积时期＞沙一段沉积时期＞沙四上亚段上部沉积时期;古湖水面:沙四上亚段上部沉积时期＞沙一段沉积时期＞沙四中亚段和沙四上亚段下部沉积时期;古生产力:沙一段沉积时期＞沙四上亚段上部沉积时期＞沙四中亚段和沙四上亚段下部沉积时期。     

松辽盆地松科1井上白垩统烃源岩有机碳含量与沉积速率的关系*

与海相盆地相比,陆相湖盆沉积物TOC和沉积速率关系的研究尚处于探索阶段,尤其是在沉积作用对TOC的控制机理研究方面还有待深入。首先运用旋回地层学方法,识别了松科1井南孔上白垩统天文周期,并利用滑动窗口频谱分析方法计算了各窗口的沉积速率及对应的TOC值。以姥鲛烷和植烷(Pr/Ph)比值作为氧化还原条件的指标,以介形虫壳体的δ¹³C作为古生产力大小的指标,对不同环境和不同古生产力条件下TOC和沉积速率的关系进行了探讨。研究表明: 在还原环境下,TOC主要取决于古生产力高低,而沉积速率的影响相对较小,当古生产力较高时,TOC值一般大于1%;反之,TOC值小于1%。但在氧化环境、低古生产力条件下,TOC随着沉积速率先增大后减小,其临界值为11,cm/ka。     

Ostracod Biostratigraphy of the Late Cretaceous Qingshankou Formation in the Songliao Basin

An ostracod biostratigraphic study was performed on 425 samples from the composite geological section constructed by using cores taken from five selected wells drilled in the Late Cretaceous Qingshankou Formation in the Songliao basin.A total of 19 ostracod zones are established in the formation,of which 3 are newly established and 3 are revised.The 19 ostracod zones are described in detail.This study provides a basis for the detailed stratigraphic division and correlation of the Qingshankou Formation and the Gaotaizi oil reservoir in the oilfield in the Songliao basin.     

Characterizing the Micropores in Lacustrine Shales of the Late Cretaceous Qingshankou Formation of Southern Songliao Basin, NE China

Micropores of shale are significant to the gas content and production potential of shale, which has been verified in the research of marine shale gas; while, few studies have been conducted on lacustrine shales. This study collected 42 samples from three wells in the Late Cretaceous Qingshankou Formation of the southern Songliao Basin, NE China, and investigated these samples by the focused ion beam-scanning electron microscope (FIB–SEM) and nitrogen adsorption analysis techniques. Four types of micropores were identified in the samples, i.e., intergranular pore, intracellular pore, organic matter pore and microfracture. The pore structure type is characterized by open slit pores and “ink type” pores which are mainly 1.5–5 nm in diameter with mesopores as the main pores. The mesopores account for 74.01% of the pore volume and 54.68% of the pore surface area. Compared with the lacustrine shales from the Triassic Yanchang Formation in the Ordos Basin and Xujiahe Formation in the Sichuan Basin, the intergranular clay mineral interlayer pores are considered to be the main reservoir space for shale gas storage in the study area, followed by intraparticle pores, organic matter pores and microfractures. Maturity and micropore are the key controlling factors which affect the shale gas content of the Qingshankou Formation in southern Songliao Basin.     

The Cretaceous Songliao Basin: Volcanogenic Succession, Sedimentary Sequence and Tectonic Evolution, NE China

The Songliao basin (SB) is a superposed basin with two different kinds of basin fills. The lower one is characterized by a fault-bounded volcanogenic succession comprising of intercalated volcanic, pyroclastic and epiclastic rocks. The volcanic rocks, dating from 110 Ma to 130 Ma, are of geochemically active continental margin type. Fast northward migration of the SB block occurred during the major episodes of the volcanism inferred from their paleomagnetic information. The upper one of the basin fill is dominated by non-marine sag-style sedimentary sequence of siliciclastics and minor carbonates. The basin center shifted westwards from the early to late Cretaceous revealed by the GGT seismic velocity structure suggesting dynamic change in the basin evolution. Thus, a superposed basin model is proposed. Evolution of the SB involves three periods including (1) Alptian and pre-Aptian: a retroarc basin and range system of Andes type related to Mongolia-Okhotsk collisional belt (MOCB); (2) Albian to Companian: a sag-like strike-slip basin under transtension related to oblique subduction of the Pacific plate along the eastern margin of the Eurasian plate; (3) since Maastrichtian: a tectonic inverse basin under compression related to normal subduction of the Pacific plate under the Eurasian plate, characterized by overthrust, westward migration of the depocenter and eastward uplifting of the basin margin.     

松辽盆地NGN1井上白垩统青山口组一段有机质演化

以NGN1井全取芯井为标杆,通过岩芯观察、地球化学分析和显微组分镜下鉴定,揭示青山口组一段的有机质演化规律。NGN1钻井位于松辽盆地东南缘,青一段由底至顶分别为灰绿色泥质粉砂岩-深灰色泥岩、油页岩-灰色泥岩-灰绿色粉砂质泥岩沉积,揭示了由滨浅湖-半深湖-滨浅湖的沉积环境演化。TOC、S2、含油率以及HI呈现增大-高值-减小的趋势,而半焦含量和块状密度则呈相反的变化趋势。青一段泥岩中主要的有机质显微组分为层状藻、孢子体和骨屑等,有机质含量与单位面积显微组分、藻类相对含量均呈明显的正相关,并结合有机质判别图解,说明有机质类型主要为I型和II1型,来源以湖泊藻类为主。泥岩中的陆源有机质含量较少,说明湖泊生物控制着有机质的来源,浅湖由于水体较浅、水底含氧,保存条件较差,导致泥岩中的有机质丰度较低,半深湖-深湖水体较深,保存条件良好,促进有机质的富集,因此垂向上沉积环境演化是导致有机质变化的主要因素。     

松辽盆地松科1井晚白垩世沉积地层有机地球化学研究

松科1井是中国大陆第一口以白垩系陆相地层为主的全取心科学探井。通过取心样品的系统地球化学分析,研究了泥岩有机质丰度、类型、成熟演化及有机质沉积环境在纵向上的变化特征。结果表明:青一段泥岩有机质丰度最高,有机碳一般大于2%,平均为3.21%,发育优质烃源岩,其次在青二、三段、姚家组和嫩江组一、二段中也均发育有机质丰度相对较高的源岩层。纵向上泥岩有机质丰度显示出从高向低的9个韵律性变化,反映了湖相沉积过程中气候与水体环境、生物发育及有机质保存条件的周期性变化。青一段泥岩有机质类型主要为Ⅰ型,较高的甾烷含量反映以藻类输入为主,较高的伽马蜡烷和低的Pr/Ph及甲藻甾烷的存在反映该时期水体具有盐度分层和强还原的沉积环境,可能与海侵有关。青二、三段泥岩有机质类型主要为Ⅰ—Ⅱ型,伽马蜡烷和Pr/Ph等多项指标反映出该时期水体呈现振荡变化,有机质受陆源影响加大。姚家组有机质类型变化大,一部分为Ⅰ—Ⅱ1型,另一部分则Ⅱ2—Ⅲ型,较高丰度的泥岩通常具有较好的有机质类型,多项指标反映出该时期沉积环境波动较大。嫩江组一、二段泥岩主要以Ⅰ型和Ⅱ型为主,4-甲基甾烷的存在反映具有沟鞭藻的贡献,较高的伽马蜡烷和低的Pr/Ph反映水体有盐度分层。有机质成熟度指标反映青二、三段中部泥岩开始进入成熟,源岩开始大量生油的深度在1500m。     

松辽盆地白垩系青山口阶缺氧事件层的有机地球化学特征

松辽盆地白垩系青山口阶下部广泛分布一套富含有机碳的黑色泥岩、页岩沉积,它具有干酪根碳同位素正偏、重排甾烷含量低,普遍存在伽马蜡烷生物标志化合物等有机地球化学特征,代表了白垩纪温室效应时间窗内古湖泊贫氧环境条件下的沉积产物。结合生物地层研究成果,认为青山口阶下部曾发生过古湖泊缺氧事件,其层位大体可与白垩纪古海洋Cenomanian-Turonian界线事件层进行对比,由此提出了松辽盆地青山口阶下部的时代归属于晚白垩世Cenomanian晚期—Turonian早期的新观点。     

松辽盆地南部上白垩统烃源岩和原油中正构烷烃的氢同位素组成研究

以松辽盆地南部上白垩统的烃源岩及原油为研究对象,对烃源岩抽提物和原油中正构烷烃的单体氢同位素组成进行了测定。生物标志化合物和正构烷烃的碳氢同位素组成特征表明,在未成熟—成熟阶段正构烷烃的单体氢同位素组成受热成熟度的影响不明显,可以作为油源对比的一个有用的辅助指标。氢同位素组成在母源判识以及重建古沉积环境方面可以提供更多的信息,与碳同位素组成结合应用具有一定的优势。     

Late Cretaceous marine fossils and seawater incursion events in the Songliao Basin,NE China

The Songliao Basin is the largest non-marine oil-bearing basin in China. Because of the absence of substantial evidence, the hypothesis of seawater incursion events into the Songliao Basin remains controversial. The presence of marine fossils could provide direct proof to support this supposition. Here, we report new discoveries of foraminifera, calcareous nannofossils, brackish dinoflagellates, and other marine and brackish-water fossils to support the suggestion of seawater incursion events in the Songliao Basin. Relatively abundant benthic and planktonic foraminifera, calcareous nannofossils, marine and brackish-water dinoflagellates, fish, and bivalves have been discovered in Members 1 and 2 of the Nenjiang Formation, a few foraminifera and brackish-water dinoflagellates have been found in the lower Qingshankou Formation, and just a few brackish-water bivalves have been found in the uppermost Qingshankou Fm. Based on the presence of marine molecular fossils and other evidence, we suggest that relatively large seawater incursion events occurred during the sedimentation of the lower Nenjiang Fm., relatively smaller seawater incursions occurred during the deposition of the lower Qingshankou Fm., and possibly a very small seawater incursion occurred during the sedimentation of the uppermost Qingshankou Fm. These seawater incursion events in the Songliao Basin were controlled by regional tectonic activity, evolution of the palaeo Songliao Lake, and global sea level change. These periodic seawater incursions brought marine biota into the palaeo Songliao Lake.     

松辽盆地东部宾县凹陷青山口组介形类生物地层与生态环境

实测松辽盆地东部宾县地区鸟河畔的两条剖面。鸟河剖面上下岩性变化较小,以灰绿色泥岩、泥质粉砂岩为主,含数层黄铁矿薄层及介形虫灰岩薄层。红石山剖面岩性岩相变化较大,下部为灰绿色,黄绿色泥岩,上部出现大套红层。通过介形类组合特征,判断出这两个剖面属于青山口期沉积。其中,鸟河剖面对应青山口组一段上部,含介形类Triangulicypris torsuosus-Triangulicypris torsuosusvar.nota组合带。红石山剖面属于青山口组二段下部,含介形类Cypridea dekhoinensis-Li mnocyrpridea copiosa组合带;及叶肢介Nenestheria sp.、Cratostracus sp.、Dictyestheia sp.,化石富集成层。通过介形类古生态分析,松辽盆地宾东地区在青一段沉积时期为浅湖环境,湖水约为半咸水至微咸水。介形类的属种单调,但优势种Triangulicypris torsuosus极为繁盛。青二段沉积时期为滨浅湖环境,湖水盐度较青一段沉积时期降低,为淡水或微咸水。生物组成以腹足、轮藻、叶肢介以及带瘤介形类的出现为特征。宾县地区在青山口组沉积时期生物具有与松辽盆地其他地区相同的化石面貌和古生态特征。其一致性表明该时期宾县地区同属于松辽盆地。青一段至青二、三段之间微体化石古生态特征发生转变,暗示松辽盆地水体条件在该沉积阶段的演变。