天然气藏与油藏形成机理及分布特征的异同

作为流体矿藏气藏与油藏的形成和分布具有相似性,都需要经过由分散到富集的成藏过程。天然气来源的广泛性和易于溶解、运移、散失的特性,决定了天然气双石油具有更多的运聚成藏方式和时空分布的广泛性。水溶对流运移、多源复合成藏、溶解气脱溶成藏、运聚动平衡成藏,是天然气运聚成藏的重要特点。     

莺歌海盆地泥-流体底辟带热流体活动对天然气运聚成藏的控制作用

莺歌海盆地是一个在新生代发育起来的南海北部被动大陆边缘的年轻高热盆地, 其高地温场及高大地热流值主要集中于盆地中部坳陷区的泥-流体底辟构造带.因此, 底辟发育演化与热流体上侵活动, 尤其是上新世晚期的热流体活动控制了天然气及CO₂的运聚与成藏特征.同时, 由于热流体上侵活动的分区分块与分层的局部性侵入, 导致了壳源型和壳幔混合型CO₂及烃类气运聚富集的分区分块与分层的局部富集特点.总之, 泥-流体底辟作用中热流体上侵活动是控制天然气尤其是CO₂运聚乃至富集成藏的主导因素, 而壳源型和壳幔混合型CO₂等非烃气与烃类气运聚成藏时间及运聚通道的差异, 则是控制和制约烃类气与非烃气差异运聚及富集成藏的关键.根据本区CO₂等非烃气与烃类气的地化特征及运聚规律, 可以分析和预测其运聚成藏模式, 为天然气勘探部署提供依据.      

连续型致密砂岩气近源累计聚集的特征及成因机制

致密砂岩气是非常规油气资源的重要组成部分,是当前技术条件下可动用程度最高的部分.致密砂岩气可分为连续型致密砂岩气和圈闭型致密砂岩气.通过系统地对比圈闭型和连续型致密砂岩气在运聚、分布上的地质、地化特征差异,并使用物理模拟实验揭示了连续型致密砂岩气呈近源累计聚集的动力学成因机制.研究表明:圈闭型致密砂岩气是天然气远距离运聚的结果,在天然气组分和碳同位素上都有很明显的分馏效应,具有良好的输导体系,形成了“常规圈闭汇聚、具有边底水、优质盖层封盖”的特征;连续型致密砂岩气是近源累计聚集的结果,天然气组分和碳同位素基本不产生分馏效应,同一地区碳同位素呈现离散性,表现出“连续分布、近源汇聚、气-水分布复杂或倒置”的特征.连续型致密砂岩气近源累计聚集是致密砂岩储层中近纳米级孔喉背景下天然气运移动阻力变化及平衡的结果.在天然气运移至气-水临界界面之前,气-水界面将天然气与地层水分为两个系统,天然气运移的动力是气体异常压力,浮力作用产生的基本条件不满足,运移阻力是上覆地层水压力和毛细管压力.连续型致密砂岩气圈闭可认为是非常规动力圈闭,其核心可概括为“(近)纳米级孔喉、气体活塞式推进、浮力基本不起作用、动阻力平衡决定气-水界面”.      

川中广安地区须家河组煤系烃源岩生气特征

川中广安气田天然气地质储量丰富,而源岩发育有限。为对其形成机理进行探讨,利用MSSV热解实验和化学动力学方法对广安地区须家河组煤系烃源岩的生气特征进行了研究。结果表明:广安地区须家河组煤系烃源岩生气主要集中在晚侏罗世(156.6~140 Ma),具有短期内大量生气的特点,生气量为(0.89~1.86)×1012m3,天然气运聚效率为7.26%以上,生气强度为(3.35~11.83)×108m3/km2,低于我国大气田通常的生气强度(20×108m3/km2)。天然气的高效运聚是广安气田在生气强度较低情况下仍能形成大气田的基础;除前人总结因素外,须家河组煤系烃源岩短期内大量生气的特点是造成该区天然气高效运聚的一个重要原因。在运聚条件优越的情况下,形成大气田所需要的烃源岩条件可适当放宽。     

塔里木东北部英南2气藏天然气运移和聚集

基于大量的地质和地球化学证据,本文详细论述了塔里木盆地塔东北地区英吉苏凹陷英南2气藏的天然气运移和聚集.研究指出:英南2气藏天然气主要来源于寒武系烃源岩,为早期聚集的寒武系来源油的裂解气.该气藏的成藏期主要为燕山末期,天然气的运移通道主要为沟通寒武系古油藏与上覆侏罗系圈闭的断裂.英南2气藏的聚集过程导致了其与邻近构造油气聚集的差异,也导致了其天然气地球化学特征上的差异.     

中国主要含气盆地天然气的运聚规律

通过对中国重点盆地大中型气田运聚规律的总结 ,可知中国大中型气田天然气的运聚具有多种途径和方式 ,归纳起来共有如下几点 :1　区域构造运动是造成天然气运移的决定性控制因素区域构造运动不但控制盆地的发育和消亡 ,而且对天然气的运移起决定性的控制作用。如区域性构造变动造成的地层产状变化 ,将旧的天然气分布格局破坏 ,天然气发生重新运移并聚集成藏。较大规模的褶皱运动一方面破坏气藏 ,也可使天然气向隆起幅度更高的部位运移 ,并在地下完整的构造圈闭中聚集成藏。区域的断裂活动 ,可极大提高天然气的垂向输道性能 ,将深部烃源岩生…     

水溶天然气运移地球化学示踪——以塔里木盆地和田河气田为例

文中选择田河气田作为研究实例,对气田东、西部天然气进行系统的天然气地球化学对比研究,结合气田成藏的地质背景,认为和田河气田具有较好的水溶气运移成藏地质条件和明显的水溶气运移地球化学证据,提出了天然气是水溶气成因的新观点。寒武系烃源岩生成的天然气在高温、高压状态下大量溶解于水,在压力的驱使下,水溶气自寒武系运移至气田东部圈闭,然后再由气田东部的高压区沿不整合面往西部的低压区运移。根据气田天然气地球化学横向变化特征,提出了ln(C1/C2)、ln(C2/C3)、CO2/CH4、CH4/N2、N2/C2H6等一系列操作性较强的水溶气运移的地球化学示踪新指标,对研究天然气成藏机理和成藏过程都有重要意义。     

天然气运移的气体同位素地球化学示踪

本文通过鄂尔多斯等含油气盆地内岩石酸解烃、罐顶气和同源多产层天然气碳同位素组成的变化，从实例剖析出发，探讨了天然气运移时气体同位素组成的变化及其对天然气运移的示踪。天然气在通过沉积地层中孔隙系统和微裂隙运移时，天然气中的甲烷碳同位素会发生一定的分馏，而乙烷以上重烃碳同位素几乎不发生分馏；在天然气层所在深度，罐顶气甲烷碳同位素组成与天然气一致，在天然气层附近，罐顶气甲烷碳同位素则明显偏离了热演化趋势线；烃源岩酸解烃与其同源的天然气重烃碳同位素组成具有较好的一致性和可比性。由此，可利用气体组分碳同位素的上述变化特征，追索天然气的运移作用。     

鄂尔多斯盆地东南部古生界天然气勘探前景

目前,鄂尔多斯盆地中北部已发现多个天然气田,为寻找新的勘探接替区域,从储集条件、烃源岩条件、封盖条件、圈闭类型、天然气运聚成藏过程和保存条件等方面入手,对鄂尔多斯盆地东南部古生界天然气的富集与成藏条件进行了全面分析,探讨了其天然气勘探前景,指出了有利勘探目标,并提出了具体的勘探部署意见。结果表明:研究区紧邻上古生界生烃中心,发育优质煤系烃源岩,生烃潜力大,气源充足,具备形成大型天然气藏的物质基础;区内奥陶系马家沟组发育有蒸发潮坪相沉积,位于北部古潜台的向南延伸带上,是下古生界天然气的有利勘探目标;南部山西组和下石盒子组发育三角洲沉积体系砂体,是有利的上古生界天然气富集区;研究区古生界发育各种隐蔽性非构造型圈闭,天然气运聚成藏过程非常有利,封盖和保存条件也很好。因此,研究区古生界具有广阔的天然气勘探前景。     

地震泵抽吸作用与油气运聚成藏物理模拟

地震泵抽吸作用是在断裂活动开启过程中,引发流体进入断裂带,并发生垂向运移的作用方式。在裂隙递进扩张形成优势裂隙并进一步发展成大的断裂面的演化过程中,地震泵抽吸作用发生,围岩中的流体在相对负压抽吸作用下进到断裂带中,之后主要在构造应力和异常高孔隙流体压力的共同作用下向上运移,并向着邻近断裂的封闭程度差、体积大、物性好的储层中充注运移,运移效率远远高于达西流和扩散流。断裂周期性破裂活动的特征决定了油气沿断裂的垂向泵吸运移呈周期性、间歇性和脉动的特点,同时也决定了油气易于在断裂错开的最新层位聚集成藏。通过克拉2气田天然气运聚成藏过程物理模拟实验结果表明,紧邻圈闭的盐下断裂为有效的天然气运移通道,穿盐断裂为无效的天然气运移通道,天然气在地震泵抽吸作用下沿断裂运移速度快、效率高,在断裂活动的短时间内可以大规模运聚成藏。     

Division of Gas Accumulation System and Laws Controlling Distribution of Natural Gas in Typical Petroliferous Basins of China

Considering the existing problems of the petroleum system, this paper brings forward the concept of natural gas accumulation system and presents the dividing principles. Then detailed statistics on the accumulation factors of the 32 typical natural gas accumulation systems in China and studies on the laws controlling distribution of gas are collected. The research shows that the petroleum accumulation system is the basic unit controlling petroleum generation, migration and accumulation. Generating intensity, generating amount, accumulating efficiency and migration distance plays an important role in the distribution of natural gas. Through analysis on results of resources evaluation, discovered reserves and residual reserves, potential areas in middle-scaled petroliferous basins in China are forecasted in this paper. Ordos, Sichuan, Tarim and Qaidam basins are found out to be the main basins developing and enriching gas accumulation systems.     

苏里格低渗砂岩大气田天然气充注运移及成藏特征

苏里格气田位于鄂尔多斯盆地伊陕斜坡西北部,属于典型的低渗砂岩大气田.苏里格气田上古生界天然气组分和碳同位素组成特征变化较小,反映其来源和成藏过程的一致性.基于对成藏地质背景、储层物性、天然气地球化学特征、烃源岩成熟度、甲烷碳同位素动力学的综合分析,认为苏里格气田天然气主要为近源充注、近距离运移和聚集,为石炭系一二叠系煤系烃源岩生成的累积聚气.天然气运移输导体系主要包括砂体一孔隙、微裂缝及小断层等,由孔隙和裂缝构成的网状输导体系在成藏过程中起了重要作用,表现为动力圈闭成藏.苏里格气田形成过程经历了早侏罗世末期、晚侏罗世至早白垩世末期、早白垩世末期至今3个演化阶段,存在下生上储和自生自储两种成藏方式.     

论塔里木盆地构造体系控油作用

塔里木盆地是多构造体系复合的大型含油气区,盆内二级构造体系控制生油拗陷和油气富集带三、四级扭动构造控制油气田。多构造体系复合型盆地油气藏特征是多含油气系统、多油气藏类型、多成藏期和油气田(藏)县4个并存等。      

Re-Examination of the Oil and Gas Origins in the Kekeya Gas Condensate Field, Northwest China–A Case Study of Hydrocarbon-Source Correlation Using Sophisticated Geochemical Methods

This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydrocarbons and biomarker fingerprints. A comparison study is also made between the geochemical characteristics of the Kekeya hydrocarbons and typical marine and terrigenous hydrocarbons of the Tarim Basin. Natural gas from the Kekeya gas condensate field is derived from Middle–Lower Jurassic coal measures while the condensates are derived from Carboniferous–Permian marine source rocks with a higher maturity. In the study area, both natural gas and condensates have experienced severe water washing. A large amount of methane was dissolved into the water, resulting in a decrease in the dryness coefficient. Water washing also makes the carbon isotopic compositions of the natural gas more negative and partially reverse. Considering that the gas maturities are higher than once expected, gas generation intensity in the study area should be much stronger and the gas related to the Jurassic coal measures could promise a greater prospecting potential. As a result of evaporative fractionation, the Kekeya condensates are enriched in saturates and lack aromatics. Evaporative fractionation disguises the original terrigenous characteristics of the light hydrocarbons associated with the natural gas, making it appear marinesourced. Thus, alteration processes should be fully taken into consideration when gas–source correlations are carried out based on light hydrocarbons. With the condensates discovered in the study area all being "migration phase", the pre-salt Cretaceous and Jurassic reservoirs may promise great exploration potential for the "residual phase" hydrocarbons. This research not only is of significance for oil and gas exploration in the southwest Tarim Basin, but also sheds light on the oil/gas-source correlations in general.     

Control Factors and Diversities of Phase State of Oil and Gas Pools in the Kuqa Petroleum System

Based on the analysis of the hydrocarbon geochemical characteristics in the Kuqa petroleum system of the Tarim Basin, this study discusses the causes and controlling factors of the phase diversities and their differences in geochemical features. According to the characteristics and differences in oil and gas phase, the petroleum system can be divided into five categories: oil reservoir, wet gas reservoir, condensate gas-rich reservoir, condensate gas-poor reservoir and dry gas reservoir. The causes for the diversities in oil and gas phases include diversities of the sources of parent material, maturity of natural gas and the process of hydrocarbon accumulation of different hydrocarbon phases. On the whole, the Jurassic and Triassic terrestrial source rocks are the main sources for the hydrocarbon in the Kuqa Depression. The small differences in parent material may cause diversities in oil and gas amount, but the impact is small. The differences in oil and gas phase are mainly affected by maturity and the accumulation process, which closely relates with each other. Oil and gas at different thermal evolution stage can be captured in different accumulation process.     

Origin of natural gases and their differences between the eastern and western parts of central Tarim Basin

The origin of natural gases in central Tarim Basin is very complicated and there has been no definite conclusion in this aspect. Based on the results of systematic research on their composition and carbon isotopic characteristics, natural gases in central Tarim Basin are composed mainly of hydrocarbon gas, Ordovician natural gas with the characteristics of crude oil-cracking gas, and Carboniferous natural gas not only originating from kerogen cracking, but also from oil cracking. There are significant differences in composition and carbon isotope of natural gases between the eastern and western areas. The causes for the differences in geochemical characteristics of natural gases are presented as follows: different thermal evolution degrees of organic matter. Natural gases in the western region may have generated from the Middle- Upper Ordovician source rocks, and natural gases in the eatern region may be derived from the Cambrian source rocks, which entered into high to over mature stages; the gases migrated from west to east and caused the different compositional and carbon isotopic characteristics of natural gases; difference in the strength of thermal sulfate reduction between the eastern and western parts, with the reduction in the eastern part being stronger than that in the western part.     

塔里木盆地北部地区主要断裂带构造应力场与油气运移

塔里木盆地北部地区的断裂构造对油气的形成、运移、储集和保存具有极为重要的控制作用。大型多期活动断裂控制了大型隆起和拗陷的形成、发展和演化,是各时期油源纵向运移的良好通道;小型或次级断裂以及由断裂产生的节理、裂隙等,可改善储层的性能,是该区各种储油构造形成的主要构造条件。
笔者认为,油气的运移和聚集最主要的条件是构造应力驱动。为了将断裂构造活动的构造应力场与油气运移的物质场结合起来,建立了构造应力驱动与岩内流体运动的理论方程,这个方程反映了构造应力、流体内压和运移势之间的微分关系。
笔者对该区已知油田不同类型断裂机制的储油构造型式、油气富集条件及部位进行了理论分析和模拟计算,进而对主要构造区块选择典型剖面模拟计算运移势状态,并与已知油田进行类比,找出油气运移和储集的有利地区,为塔北地区油田勘探提出了预测意见。      

塔里木盆地海相石油的真实勘探潜力

塔里木盆地古生界蕴藏了丰富的海相油气资源,储集层目前埋深在5500～10000m。深部流体的相态或者说液相石油大量消失的深度下限是学术界比较关心的理论问题,而塔里木盆地海相到底富油还是富气也是关系到塔里木油田未来产能规划的现实问题。通过对塔里木盆地原油的热稳定性分析,特别是低地温梯度和晚期快速深埋过程的补偿效应研究,认为液态石油大量消亡(油裂解成气)的深度下限在9000～10000m以下,对应的储层温度大于210℃,在此深度之上液态石油可以大量存在。通过对油气聚集与保存的关键地质科学问题的研究,认为晚海西期是台盆区油藏的主要成藏期,烃源灶区生成的油气主要分布在稳定的古隆起及其围斜区域;而晚海西期这些古隆起及其围斜区碳酸盐岩储层埋藏深度在800～2500m范围内,岩溶储集体发育,这是台盆区形成大面积层状油气聚集的基础,也决定了现今埋深在7000～9000m深度范围内的斜坡区将成为黑油和凝析油的重要勘探接替区。     

塔里木盆地西南边缘压扭构造体系及其石油地质意义

塔里木盆地西南边缘发育甫沙-齐姆根和柯克亚-和田南2个压扭构造体系,前者主要是帕米尔弧形构造东北侧的侧向滑移与西昆仑造山带向塔里木盆地的不均匀冲断活动的联合作用结果,后者则主要与西昆仑造山带向塔里木盆地的不均匀冲断作用有关。这两个压扭构造体系主体形成于新近纪以来的喜马拉雅运动,其构造样式在平面上主要为走滑-逆冲断裂和雁列式分布的断裂与背斜,在剖面上则呈现为双重构造与反冲构造的叠加。压扭构造带所遭受的压扭作用从改善储层的储集性能、形成新的油气圈闭、促进油气运移与成藏等方面对塔里木盆地西南边缘的油气成藏发挥了积极作用,压扭构造带是油气勘探的有利构造部位。