A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin,Northeastern China

A continuous terrestrial succession was recovered from the Songke-2(SK-2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke-1(SK-1) core. In this study, thorium(Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi-periodically; power spectr...     

姬塬地区长8油层组浅水三角洲沉积特征

姬塬地区位于鄂尔多斯盆地中偏西部地区,晚三叠世主要受北东、北西及南部三个方向的物源控制。通过岩心观察、薄片鉴定、测井曲线等资料的综合分析,对研究区上三叠统长8油层组岩石类型、沉积构造、物源方向、古生物和沉积相特征进行了详细研究,发现长8沉积时期姬塬地区地形平缓,河流作用较弱,主要发育一套浅水三角洲沉积体系,其沉积作用和砂体展布受湖平面升、降和物源方向控制明显,对油气成藏有着重要的意义,表现为:①湖平面上升期,湖岸线快速向物源方向迁移,以发育长条状和鸟足状水上—水下分流河道砂体为主;②下降期以发育三角洲平原为主,来自不同物源方向的前缘砂体在研究区中部交汇;③湖平面上升期水下分流河道砂体呈席状发育以及岩性遮挡条件更好,因而比湖平面下降期发育的砂体更有利于形成岩性油藏。     

河南省济源盆地下侏罗统鞍腰组重力流沉积特征及其构造意义*

在详细野外剖面工作的基础上,通过岩性特征、沉积构造及沉积序列等的系统观察研究,发现济源盆地下侏罗统鞍腰组重力流沉积由滑塌沉积、砂质碎屑流沉积和浊流沉积构成。滑塌沉积以砂岩和泥岩的混杂、岩层的滑动变形以及泥岩呈碎块被卷入砂岩层中为特征;砂质碎屑流沉积常呈厚层块状,颗粒分选和磨圆较差,杂基较多,可见漂浮于层内的石灰岩砾石;常见的浊流沉积分为2种类型: 具有明显正粒序结构的浊流沉积和砂泥岩薄互层的浊流沉积,可用鲍马序列来描述。鞍腰组重力流沉积可划分为3个沉积序列: 序列A记录了滑塌沉积→砂质碎屑流沉积→浊流沉积→深湖沉积的转换过程;序列B表现为砂质碎屑流与浊流沉积的叠覆;序列C由浊流及湖泊沉积构成,并经历了由序列A→序列B→序列C的沉积演化过程。重力流的形成受秦岭造山带于早侏罗世沿三门峡—鲁山—舞阳断裂发生逆冲推覆作用的控制,其沉积演化指示了秦岭造山带造山作用由强到弱的过程。     

四川盆地碳酸盐岩油气勘探实践与认识

四川盆地烃源十分丰富。但油气演化程度高,大多已进入高成熟和过成熟阶段,至今只在侏罗系发现有油藏,三叠系及其更老地层皆为气藏。储层主要为碳酸盐岩,其特点是低孔低渗,平均孔隙度仅1.7%,平均渗透率小于1×10~(-3)μm~2,但其中的“孔洞发育层段”平均孔隙度可达3%～6%。根据四十年的勘探经验,加强预探并争取新发现是四川盆地油气勘探发展的关键。预探中,按构造带规划大中型气田勘探目标,将成藏条件相似、地域上相邻的局部圈闭群作为一个整体勘探对象,实行稀井广探,少井高效。“八五”以来,在高陡构造带勘探技术、储层横向预探技术等方面有长足的进步,勘探成效不断提高,实现了资源序列的良性循环。     

Origin and depositional environments of source rocks and crude oils from Niger Delta Basin: Carbon isotopic evidence

Thirty-nine crude oils and twenty-one rock samples from Niger Delta Basin, Nigeria have been characterized based on their isotope compositions by elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry. The bulk carbon isotopic values of the whole rock extracts, saturate and aromatic fractions range from –28.7‰ to –26.8‰, –29.2‰ to –27.2 ‰ and –28.5 ‰ to –26.7 ‰, respectively while the bulk carbon isotopic values of the whole oils, saturate and aromatic fractions range from –25.4 ‰ to –27.8 ‰, –25.9 ‰ to –28.4 ‰ and –23.5 ‰ to –26.9 ‰, respectively. The average carbon isotopic compositions of individual alkanes (nC₁₂-nC₃₃) in the rock samples range from –34.9‰ to –28.2‰ whereas the average isotopic values of individual n-alkanes in the oils range from –31.1‰ to –23.8‰. The δ¹³C isotope ratios of pristane and phytane in the rock samples range from –29.2 ‰ to –28.2 ‰ and –30.2 ‰ to –27.4 ‰ respectively while the pristane and phytane isotopic values range from –32.1‰ to –21.9‰ and –30.5‰ to –26.9‰, respectively. The isotopic values recorded for the samples indicated that the crude oils were formed from the mixed input of terrigenous and marine organic matter and deposited under oxic to sub-oxic condition in lacustrine-fluvial/deltaic environments. The stable carbon isotopic compositions were found to be effective in assessing the origin and depositional environments of crude oils in the Niger Delta Basin.     

南黄海盆地中部隆起的形成与演化

南黄海盆地是在前震旦系克拉通基础上发育的中、古生界海相与中、新生界陆相多旋回叠合盆地。通过地震资料解释,结合邻区钻井与区域地质资料,对南黄海盆地中部隆起中、古生代地层及其形成演化进行了研究,结果表明,南黄海盆地中部隆起沉积了较全的中、古生界海相地层,发育第四系—新近系、中—下三叠统青龙组、上二叠统、下二叠统—上泥盆统、中—下志留统,奥陶系—震旦系和前震旦系变质岩系等7套地震地质层序;主要经历了前震旦纪基底形成、震旦纪—早古生代克拉通发育、晚古生代—中三叠世稳定台地—陆内裂陷、晚三叠世—古近纪形成与抬升剥蚀及新近纪-第四纪坳陷沉降5个阶段。     

松辽盆地滨北地区油气运移输导体系分析

传统的围绕生烃洼陷的油气勘探在滨北地区受到了严峻的考验,面积占整个松辽盆地1/3的滨北地区的油气勘探一直没有取得突破性进展.分析认为滨北地区存在三大背斜构造带(绥棱背斜带、乾元背斜带和克山-依龙背斜带)和滨州走滑断裂带所构成的输导体系.三大背斜带的形成和定型均早于盆地青山口组主力烃源岩大规模生排烃时间(白垩纪末),并分别倾没于齐家-古龙凹陷北部、黑鱼泡凹陷和三肇凹陷,凹陷生烃潜力的差异决定了紧邻输导体系油气勘探潜力的差异,其中齐家北凹陷和三肇凹陷已经发现了较丰富的油气资源,决定了绥棱背斜带和克山-依龙背斜带油气勘探的潜力较大.乾元背斜带临近黑鱼泡凹陷,由于黑鱼泡凹陷烃源岩成熟度低,烃源岩没有进入大规模生排烃阶段,因此勘探潜力有限;滨州走滑断裂带横穿齐家-古龙凹陷和三肇凹陷,断裂活动时间与烃源岩成熟时间一致,有利于油气的定向运移,同时晚期构造活动西段强而东段弱,从油气保存的角度看,有可能东段优于西段,但从油气的垂向运移看,西段更有可能形成垂向上多层系含油的复式油气聚集带,因此沿整个滨州走滑断裂带是有利的勘探领域.     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

准噶尔盆地玛湖凹陷百口泉组砾岩储层特征及其主控因素

综合岩心观察、薄片鉴定及场发射扫描电镜、Quemscan软件、X-衍射、阴极发光、图像分析等分析测试手段,并结合测井、录井和物性等资料,从沉积和成岩两方面对准噶尔盆地玛湖西斜坡百口泉组砾岩储层特征与有利储层的主控因素进行了综合研究。研究表明：砾岩储层骨架颗粒的成分、粒度、分选性和砾岩体的厚度主要由物源和沉积环境共同决定,这些因素控制了埋藏期的压实作用和钙质胶结作用的强弱、成岩环境的特征、孔隙流体的性质、钾长石溶蚀作用以及火山碎屑的蚀变对储层性质的影响。相对扇三角洲平原亚相的水上河道和河道间,发育在扇三角洲前缘亚相的水下分流河道微相的储层厚度较大,刚性颗粒含量高、分选好,易发育绿泥石膜,压实作用相对较弱,孔隙较大且连通性较好,孔隙流体流动性较好,因此,钾长石和岩屑等易溶矿物的溶蚀产物如高岭石、伊利石等自生黏土矿物易被带出而不在原地发生沉淀,对储层物性的改善具有十分重要的作用。此外,处于有机质优势运移方向的储层物性较好。     

日本海天然气水合物气源成因及主控因素探讨

为了探讨日本海天然气水合物的气源成因及其控制因素, 收集和整理了日本海西南郁陵盆地和日本海东缘上越盆地及邻近的相关资料。结果显示,上越盆地及邻近海域甲烷羽状流、麻坑、自生碳酸盐岩及地震剖面上“气烟囱”和BSR等发育,块状水合物出露海底为热解成因;郁陵盆地羽状流不太发育,而自生碳酸盐岩和地震剖面上的“气烟囱”较发育,钻孔发现的水合物主要为生物成因。结合日本海构造演化特征综合分析认为,日本海东缘热解成因水合物的主控因素是近S—N向和近E—W向交互断裂作用以及NE—SW向的晚期构造挤压;日本海西南海域生物成因为主兼热解成因水合物的主控因素是NEE—SWW向的晚期构造挤压;而日本海西北海域构造定型早且缺少晚期构造挤压,因此,推测其水合物气源应该主要为生物成因,热成因的可能性很小。