四川盆地金秋气田:一个典型以中生界沉积岩为氦源岩的含氦-富氦气田

氦气成藏长期以来研究较少,成藏条件与成藏机理还不十分清楚,氦源岩类型和形成条件争议较大。通过解剖含氦-富氦的金秋气田认为:(1)金秋气田氦气含量主要分布在0.05%~0.10%,平均为0.07%,部分井含量超过0.10%,最高为0.20%。同位素分析认为氦气为壳源成因,没有幔源的贡献。(2)金秋气田是一个典型以中生界沉积岩为氦源岩的含氦-富氦气田。上三叠统须家河组和侏罗系具有较高的铀、钍元素含量和较大的地层厚度,在金秋地区具有较高的氦气生气强度,是形成含氦-富氦气藏的氦源基础。氦气应该主要来源于侏罗系储层,而非上三叠统须家河组烃源岩层系。(3)金秋气田含氦-富氦气田的形成受3个主要因素控制,具有高氦气生气强度的氦源岩提供了很好的物质基础;具有适度充注强度的烃类气体的存在有利于氦气富集;地层抬升剥蚀温、压下降导致的原位溶解氦气脱溶作用是氦气富集的有益补充。

四川盆地蓬莱气区震旦系灯影组二段岩溶古地貌与控储模式

基于钻井岩心描述、薄片鉴定、测井资料以及三维地震资料,对四川盆地蓬莱气区震旦系灯影组二段(灯二段)表生岩溶古地貌与储层发育规律进行系统研究。结果表明:(1)蓬莱气区灯二段垂向上可划分为地表岩溶带、垂直渗流带、叠合带、水平潜流带和深部缓流带,其中水平潜流带发育储层厚度最大。(2)采用双界面法恢复了蓬莱气区灯二段岩溶古地貌,划分为4个一级古地貌单元:岩溶高地、岩溶斜坡、岩溶洼地和岩溶盆地,整体表现为“一高、一斜、两洼”的古地貌特征。(3)东部高石梯—磨溪地区为岩溶高地,中部发育岩溶斜坡,西北侧及西南侧为岩溶洼地。岩溶高地主要发育垂直渗流带,岩溶斜坡主要发育水平潜流带。蓬莱气区灯二段储层的发育由岩溶古地貌与沉积相联合控制。(4)表生岩溶储层是四川盆地蓬莱气区灯二段的主要储层类型,岩溶斜坡叠合丘滩体微相形成了优质储层。

深层—超深层碎屑岩储层非均质性特征与油气成藏模式

深层—超深层地质条件下,储层的孔渗物性特征和流体动力连通关系决定了油气在储层中的流动状态,这也就决定了油气运移的动力条件和聚集成藏的机理与过程。本文基于对深层—超深层碎屑岩储层结构非均质性的研究,认识深层—超深层油气运聚成藏机制和过程,总结油气多期复合成藏模式,探索深层—超深层油气分布规律。碎屑岩储层普遍存在强烈的非均质性,受到沉积结构构造及成岩作用控制,表现出空间结构性特征,在埋藏至深层—超深层的过程中经历了差异性的成岩演化和油气充注。结构非均质性储层中的油气总体向上倾方向运移,受储层中砂体分布、隔夹层结构以及连通方式的影响,油气运移路径的分布极不均匀,在储层中任何部位都可能聚集,并可能继续运移到有利圈闭中富集。在深埋过程中,多期多幕的构造变动促使深层—超深层储层中已聚集的油气向着上倾方向运移调整,或沿着断裂向上运移调整至中—深层与之相关的有效储层中运移、聚集。深层—超深层勘探具有更为广泛的目标选择,洼陷区和斜坡区都可能成为有利勘探区域。现实的深层—超深层油气勘探新领域包括:构造高点油气藏向供源方向的拓展,深层—超深层烃源由断裂调整至中深层—超深层的次生油气聚集,深层—超深层与油气源相关的斜坡带以及深层—超深层生烃洼陷优质烃源岩层内部及相邻的有效储层。

四川盆地中部—北部地区灯影组二段天然气勘探新认识及潜力分析

近期PT101井灯影组二段测试获得231×10^(4)m^(3)/d的高产工业气流,刷新了四川盆地灯影组探井测试产量纪录,显示川中古隆起北部构造斜坡区灯二段具备规模资源。利用最新的钻井岩电、地震及分析测试等资料,针对川中—川北地区灯二段含油气地质条件进行新一轮研究,明确了川中—川北地区灯二段台地边缘带勘探潜力。研究表明:(1)川中—川北地区灯二段发育由南向北逐渐变宽、增厚的台地边缘沉积,台缘带宽40~130 km,厚650~1000 m;(2)川中—川北地区灯二段储层以台地边缘丘-滩复合体藻白云岩为主,发育次生溶蚀孔、洞、缝,平均孔隙度为3.6%,平均渗透率为3.6×10^(-3)μm^(2),优质储层呈大面积连片叠置分布;(3)川中-川北地区灯二段源储配置条件极佳,中江—蓬莱区块发育多个大型断控构造-岩性圈闭,已证实PT1井区、ZJ2井区具有独立的气-水界面并且远低于高石梯—磨溪地区,发育大型单斜构造背景下的岩性、构造-岩性气藏群。川中-川北地区灯二段台地边缘带具有有利的沉积背景、良好的储层发育条件及优越的天然气成藏要素配置关系,是四川盆地灯影组发现下一个万亿方气区的重要战略新区带。

迪北气藏侏罗系阿合组烃包裹体特征及成藏分析

迪北气藏侏罗系阿合组储集层共见到2期烃包裹体:Ⅰ期发黄色荧光的烃包裹体和Ⅱ期发蓝白色荧光的烃包裹体。根据包裹体光性特征和组分分析:Ⅰ期烃包裹体为成熟的中质油,Ⅱ期烃包裹体为成熟—过成熟的轻质凝析油。油源对比认为,形成这2期烃包裹体的主力烃源岩是阳霞凹陷三叠系湖相烃源岩。通过包裹体测温、捕获深度计算及埋藏史恢复,Ⅰ期烃包裹体形成于中新统康村组沉积早—中期(17—10 Ma),Ⅱ期烃包裹体形成于中新统康村组沉积晚期—库车组沉积中期(10—5 Ma)。迪北气藏所在的依奇克里克构造带自中新世以来快速沉积,快速沉降,导致其具有多期连续成藏的特点,先后形成Ⅰ期和Ⅱ期油气的聚集。

利用自然伽马测井估算塔里木盆地沉积层生热率

盆地的热体制研究对盆地构造演化与油气勘探意义重大。岩石放射性生热率是岩石重要的热物性参数,是研究盆地热体制的基础数据之一。不同于传统的分析测试方法,自然伽马(GR)—生热率(A)换算只需要GR测井就可以计算生热率。笔者利用塔里木盆地不同地区20口主要钻井的GR测井数据计算了沉积层共6094个生热率数据,建立了代表性钻井岩性测井—生热率对比图、塔里木盆地地层生热率柱,估算了盆地沉积层放射性生热对地表热流的贡献及对深部地层的增温效应。结果表明,塔里木盆地沉积层的平均生热率为1.17±0.336μW/m^3,岩性是地层生热率的主控因素,泥岩生热率最高,为1.96±0.318μW/m^3,砂岩次之,为0.99±0.264μW/m^3,白云岩和灰岩生热率较低,分别为0.44±0.362μW/m^3和0.36±0.408μW/m^3。根据地层生热率,估算沉积层生热贡献的热流为9.36mW/m^2,约占地表总热流的21%,沉积层生热对地温梯度的贡献约为3.3℃/km,放射性生热对属于"冷盆"的塔里木盆地的地温场具有不容忽视的影响。

塔里木盆地早寒武世风化—热液耦合过程及其地质意义

以塔西北下寒武统玉尔吐斯组黑色页岩为例,利用总有机碳(TOC)、热解、干酪根碳同位素、主量元素、微量元素及稀土元素等测试分析,探讨风化作用、热液活动及其对有机质富集的影响。结果表明:风化—热液耦合过程促进下寒武统富有机质页岩的发育。古风化作用为海洋生物生长提供必需的营养元素(Fe)和丰富的陆源碎屑,前者导致浮游生物的勃发,后者促进水体有机质的吸附和沉降,为有机质富集奠定物质基础;热液活动提供丰富的还原性气体(H_(2)S)和热液硅,前者创造硫化缺氧的沉积环境及透光厌氧带,促进沉积有机质的保存,后者稀释沉积有机质的丰度。当风化作用较强而热液活动较弱时,古生产力勃发,热液硅稀释作用较弱,促进黑色富有机质页岩的发育;当热液活动较强而风化作用较弱时,古生产力受限,热液硅稀释作用较强,导致相对贫有机质硅质页岩的形成。塔西北下寒武统烃源岩的发育模式受风化—热液协同控制。芳基类异戊二烯烃的油源对比显示,风化—热液耦合控制下发育的富有机质烃源岩对塔里木盆地丰富的深层油气资源具有重要贡献。该结果对塔里木盆地深层油气勘探具有参考意义。

Origin of the unusually high dibenzothiophene concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin,China

The origin of the unusually high dibenzothiophene （DBT） concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin was studied by Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）.The most abundant sulfur compounds in the oils are S 1 species with doublebond equivalent （DBE） values of 1-19 and 11-48 carbon atoms.The range of the number of carbon atoms in the sulfur compounds detected by the FT-ICR MS （S 1 species with DBE=9） is about ten times larger than that for sulfur compounds detected by GC/MS （DBTs）.This suggests that FT-ICR MS is a much better approach than GC/MS for characterization of DBTs in crude oils.The abundance of S 1 species with DBE=1-8 decreased with increasing thermal maturity,while the abundance of S 1 species with DBE=9 （primarily DBTs） increased.Therefore,thermal maturity is an important factor in the formation of oils with high DBT concentrations.Unusually high abundances of S 1 species with low DBE values （1-8）,which include sulfide,thiophene and benzothiophene,were observed in several oils,especially the TZ83 （O 1） oil with high or very high thermal maturity.Thermochemical sulfate reduction （TSR） was thought to be the reason for the high abundance of these low DBE compounds in deep reservoirs,and thermochemical sulfate reduction could affect the distribution and composition of DBTs in the oils.According to the results of FT-ICR MS analysis,there are no signs that TSR is occurring or has occurred recently for most of the Lower Ordovician oils.

Oil-source rock correlation and quantitative assessment of Ordovician mixed oils in the Tazhong Uplift, Tarim Basin

The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.

Origin of the Silurian Crude Oils and Reservoir Formation Characteristics in the Tazhong Uplift

The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution. For this reason, the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area. Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks, i.e., heavy oils are distributed in the TZ47-15 well-block in the North Slope while normal and light oils in the No. I fault belt and the TZ16 well-block, which means that the oil properties are controlled by structural patterns. Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks, suggesting a good genetic relationship. However, the compound specific isotope of n-alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the Mid- Upper Ordovician and the Cambrian-Lower Ordovician source rocks. Most Silurian oils have a record of secondary alterations like earlier biodegradation, including the occurrence of ＂UCM＂ humps in the total ion current （TIC） chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils, and regular changes in the abundances of light and heavy components from the structural low to the structural high. The fact that the Silurian oils are enriched in chain alkanes, e.g., n-alkanes and 25-norhopane, suggests that they were mixed oils of the earlier degraded oils with the later normal oils. It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions. The migration and accumulation models of these oils in the TZ47-15 well-blocks, the No. I fault belt and the TZ16 well-block are different from but related to each other. The investigation of the origin of the mixed oils and the hydrocarbon migration and accumulation mechanisms in different charging periods is of great significance to petroleum exploration in this area.

Origin of Crude Oil in the Lunnan Region,Tarim Basin

The oil source of the Tarim Basin has been controversial over a long time. This study characterizes the crude oil and investigates the oil sources in the Lunnan region, Tarim Basin by adopting compound specific isotopes of n-alkanes and biomarkers approaches. Although the crude oil has a good correlation with the Middle-Upper Ordovician （02＋3） source rocks and a poor correlation with the Cambrian-Lower Ordovician （C-O1） based on biomarkers, the ~3C data of n-alkanes of the Lunnan oils show an intermediate value between C-O1 and 02＋3 genetic affinity oils, which suggests that the Lunnan oils are actually of an extensively mixed source. A quantification of oil mixing was performed and the results show that the contribution of the Cambrian-Lower Ordovician source rocks ranges from 11% to 70% （averaging 36%）, slightly less than that of the Tazhong uplift. It is suggested that the inconsistency between the biomarkers and od3C in determining the oil sources in the Lunnan Region results from multiple petroleum charge episodes with different chemical components in one or more episode（s） and different sources. The widespread marine mixed-source oil in the basin indicates that significant petroleum potential in deep horizons is possible. To unravel hydrocarbons accumulation mechanisms for the Lunnan oils is crucial to further petroleum exploration and exploitation in the region.

Key oil accumulation periods of ultra-deep fault-controlled oil reservoir in northern Tarim Basin, NW China

A giant fault-controlled oilfield has been found in the ultra-deep(greater than 6000 m) Ordovician carbonate strata in the northern Tarim Basin. It is of great significance for hydrocarbon accumulation study and oil exploitation to determine the key oil accumulation periods. Based on detailed petrographic analysis, fluid inclusion association(FIA) in calcite samples filling in fractures from 12 wells were analyzed, and key accumulation periods of the strike-slip fault-controlled oilfield was studied by combining oil generation periods of the source rocks, formation periods of the fault and traps, and the fluid inclusion data.(1) There are multiple types of FIA, among them, two types of oil inclusions, the type with yellow fluorescence from the depression area and the type with yellow-green fluorescence from the uplift area with different maturities indicate two oil charging stages.(2) The homogenization temperature of the brine inclusions in FIA is mostly affected by temperature rises, and the minimum temperature of brine inclusions symbiotic with oil inclusions is closer to the reservoir temperature during its forming period.(3) FIA with yellow fluorescence all have homogenization temperatures below 50 ℃, while the FIA with yellow-green fluorescence have homogenization temperatures of 70–90 ℃ tested, suggesting two oil accumulation stages in Middle-Late Caledonian and Late Hercynian.(4) The Middle-Late Ordovician is the key formation period of the strike-slip fault, fracture-cave reservoir and trap there.(5) The oil generation peak of the main source rock of the Lower Cambrian is in the Late Ordovician, and the oil accumulation stage is mainly the Late Ordovician in the depression area, but is mainly the Early Permian in the uplift area. The key oil accumulation period of the strike-slip fault-controlled reservoirs is the Late Caledonian, the depression area has preserved the primary oil reservoirs formed in the Caledonian, while the uplift area has secondary oil reservoirs adjusted from the depression area during the Late Hercynian. Oil reservoir preservation conditions are the key factor for oil enrichment in the strike-slip fault zone of northern Tarim, and the Aman transition zone in the depression is richer in oil and gas and has greater potential for exploration and development.

中下寒武统海相地层地球化学特征及油气地质意义——以塔里木盆地柯坪地区为例

为了进一步研究塔里木盆地寒武系海相地层垂相上的沉积环境演化特征和油气地质条件,本文以塔西北柯坪地区肖尔布拉克剖面中、下寒武统为研究对象,通过镜下观察、主量元素、微量元素、稀土元素以及碳氧同位素测试分析,探讨了该套地层的地球化学特征、沉积环境以及油气地质意义,并为地层对比提供依据以及在全球背景下碳同位素负漂移的原因进行分析,认为塔里木盆地寒武系油气生、储、盖层的发育受控于沉积环境的演化.研究结果表明:1)氧化还原指标Th/U,Ni/Co,δU等指示寒武系玉尔吐斯组、肖尔布拉克组、沙依里克组为缺氧的沉积环境,吾松格尔组为氧化环境,阿瓦塔格组指示强烈的氧化环境,其氧化还原环境受海平面变化的控制;2)玉尔吐斯组存在明显δEu正异常,δEu值高达61.60,并且大量富集Ba和Zn元素,结合主量元素协变图,认为受到热液作用的影响,热液作用携带的大量营养元素促进生物勃发,有利于有机质生成;而缺氧的沉积环境有利于有机质的保存,玉尔吐斯组有机质的富集主要受控于氧化还原条件;3)中-下寒武统分界线处存在着明显的δ^(13)C负漂移("ROECE"事件),δ^(13)C的漂移幅度为9.21‰,结合微量元素分析,认为是发生全球性海平面上升过程中,底层δ^(13)C亏损的缺氧水体上涌导致,研究区的δ^(13)C负漂移可与全球其他地区的"ROECE"事件进行对比,可作为地层对比的依据;4)玉尔吐斯组形成于缺氧的盆地-斜坡环境,富集大量有机质,是优质的烃源岩层;肖尔布拉克组发育于高能的台地边缘斜坡环境,其中-上段的微生物碳酸盐岩是良好的储集层;阿瓦塔格组形成于强烈氧化的蒸发环境,膏岩层发育,可作为有效的盖层;玉尔吐斯组的优质烃源岩、肖尔布拉克组的微生物碳酸盐岩以及阿瓦塔格组的膏岩层构成一套良好的生储盖组合,具有优越的成藏条件,是深层油气勘探的有利区带.