焉耆盆地油气形成条件与分布规律

【作者】 姚亚明；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2004， 博士

【摘要】 焉耆盆地地处新疆塔里木、准噶尔和吐哈三大盆地之间，构造位置处于南天山褶皱带东端，是在海西期褶皱基底上发育起来的中新生代含油气、含煤沉积盆地，面积13000km~2。盆地具有两坳—隆的构造格局，自南而北划分为博湖坳陷、焉耆隆起、和静坳陷三个一级构造单元。盆地沉积盖层由中生界三叠系、侏罗系、新生界第三系、第四系组成，侏罗系是其主要勘探目的层。河南油田自1993年9月开始对其开展规模性油气勘探，到2003年底，发现并探明两个油田(宝浪、本布图)、四个含油区块(宝中、宝北、本布图、本布图东)，累计含油面积23.5km~2，探明石油地质储量4172×10~4t(油当量)，建成原油生产能力23×10~4t，累计生产原油122×10~4t、天然气3.4×10~8m~3。不但证明了焉耆盆地是一个含油气盆地，而且还表明了该盆地是富集程度比较高、含油且含气的、具有良好油气勘探前景的一个盆地。焉耆盆地开展勘探工作十年来，在油气勘探取得突破和发现的同时，也获得了大量的地质资料，在此基础上开展的油气形成条件和分布规律研究，无论是对于总结这种现今小型含煤盆地的成烃成藏地质规律、还是对于指导焉耆盆地的进一步油气勘探工作都是十分有意义的。论文总的指导思想是以现代石油地质理论为指导，坚持从整体、动态、综合这一思路出发，始终贯彻成盆、成烃、成藏这一主线，立足于改造型盆地、高地温梯度、煤系地层成烃这一特点，运用残留盆地油气成藏系统评价思路，采用平衡剖面复原和多种测试新技术，研究成烃、成藏过程各要素及其相互关系，分析油气成藏的主控因素和油气的分布规律，取得了如下新的成果和认识： 1、在区域地质背景分析上，提出焉耆盆地的形成演化与天山造山带构造演化有密切的成因联系，并且是横跨在具有不同构造性质和演化历史的南天山构造带和库鲁克塔格之上，导致盆地结构、构造演化明显受其基底构造的控制，使盆地以焉耆断裂为界具有南北分带的深部结构特征。盆地北部基底属于南天山构造带，由大面积分布的中泥盆统和海西期花岗岩组成，为一被动陆缘坳陷带；盆地南部基底为库鲁克塔格区的地层建造，主要包括前震旦纪的结晶基底和古生代未变质地层。 2、在盆内构造形态研究上，阐明盆地内构造主要由近东西向的挤压构造带和北西向的变换构造带组成，反映出构造变形具有南北分带、东西分块的菱形构造格局特征。根据盆地内构造的复原结果分析，结合区域构造背景及盆地沉积建造特征，可以将焉耆盆地中新生代的演化划分为三个主要阶段，即燕山早、中期弱伸展阶段，燕山晚期强烈挤压阶段和喜山期对冲构造格局形成阶段。 3、沉积和层序地层学研究表明，焉省盆地沉积盖层由中生界三亚系、侏罗系，新生界第三系、第四系组成，侏罗系含煤碎屑岩系是其主要勘探目的层.侏罗系可划分为辫状河一三角洲、曲流河一滨浅湖以及湖泊一三角洲等三种层序类型，每一种层序类型可划分出低水位、水进和高水位体系域，代表了侏罗纪沉陷期的典型层序一体系域类型. 4几盆地热史与古地温分析认为，焉省盆地热演化史明显不同于西部其它盆地，表现为现今地温梯度:北部凹陷平均为3.48℃/l00米，南部凹陷平均为3.06℃/100米，比相邻的塔里木盆地1.8一2.5℃/100米、吐哈盆地2.36℃/100米明显要高.针对现今地温梯度较高的特点，从沉积盖层放射性元素含量、大地热流值等方面进行分析，从U、Th、K刃等放射性元素的含t不高、而大地热流值达到89mv/m，看，认为地温梯度高的原因来自地内深处，与焉奢断裂一霍拉山断裂对深部热源的沟通引起热源上升密切相关. 5、侏罗系煤系源岩评价与成烃机理研究表明，侏罗系煤系烃源岩有泥岩、碳质泥岩和煤岩，既生成原油，又能生成一定量的天然气，本区煤成烃的主要贡献组分为墓质镜质体，生_烃潜力八道湾组最优，西山窑组次之，三工河组最差，有机质类型属典型的腐殖型，仅部分碳质泥岩和泥岩可达腐泥一腐殖型。侏罗系烃源岩均己进入成烃门限，门限深度北部凹陷为Z000m，南部凹陷为123Om，镜质体反射率为0.6~1.1%，处于液态生油窗范围，处于生油高峰期.油源对比研究表明，本区煤系烃源岩产烃率以泥岩最高，煤岩次之，碳质泥岩最差，生烃仍以煤系泥岩为主.通过与相邻的吐哈盆地、准噶尔盆地和塔里木盆地烃源岩特征进行对比，焉奢盆地泥岩类有机质丰度、资源丰度最高，其次为吐哈盆地，而有机质类型和成熟度则三个盆地相当. 6、烃源岩的生烃史、流体包裹体、储层自生伊利石同位素年代学、油气成熟度综合分析结果表明，焉奢盆地侏罗系油气藏具有二期成藏的特点，第一期发生在晚白至世早、中期，是盆地的主要成藏期，第二期发生在第三纪，是盆地的次要成藏期，本期仅发生在博湖坳陷的北部凹陷.在此基础上提出侏罗系含油气系统经历了晚白至世早、中期形成阶段和第三纪活化一再造阶段。 7、总结出焉奢盆地油气成藏主控因素及油气分布规律为:油气紧邻主力生油次凹分布，位于生烃中心附近的构造带是油气运移聚集的主要区带;构造变形的分带性决定了博湖坳陷南北凹陷油气分布的差异性;中新生代继承性发展，后期保存条件较好的二?更多还原

【Abstract】 Yanqi basin is among Tarim basin, Junggar basin and Turpan basin, lying in the east of Tianshan drape zone It is a Mosozoic and Cenozoic coal basin growing from Haixi drape base and its area is 13000km2. The basin takes on a layout of two depressions and one uplift. From south to north the basin has three No. I tectonic units named respectively: Bohu depression, Yanqi uplift and Hejing uplift. Sediment cover consists of Trias, Jurassic, Tertiary and Qaternary, but Jurassic is the mainly exploited stratum. Henan oil field started to cosmically exploit in September in 1993 and fond two oil fields(Biaoliang oil field and Bengbutu oil field) and four oiliness sections(Baobei, Baozhong.Bengbutu and Bengbutudong), the whole area of oiliness come to 23.5×104t, discoverable geologic reserves of oil come to 4172×104t, produce ability of crude oil come to 23×104t, its accumulation output of crude oil and gas respectively come to 122×104t and 3.4×108m3. These prove that Yanqi basin is not only a oil-gas basin, but a preferable enrichment, containing oil and gas and preferable exploited foreground basin. Since the exploration in the basin for 10 years, We have got great many geologic data when we obtain breakout and finds. On these base, the study on forming condition and distribution rule of oil and gas has great meaning on summarizing geologic rule of forming- hydrocarbon and pool-forming of these small basin containing coal and on the further exploited work of Yanqi basin. With the guide of modern petroleum geologic rule, insisting the thought of integer, dynamic and integration, carrying through forming-basin, forming-hydrocarbon and pool-forming and being established in the characteristic of reformed basin, high ground temperature grads, coal stratum forming hydrocarbon, using the appraise thought of petroleum pool-forming system of relict basin, using comeback of balance profile and many new technology of testing, studying on each element and interrelation in the course of forming-hydrocarbon and pool-forming and analyzing main controlling factor and oil-gas distribution rule, we obtain viewpoint and conclusion as follow:1.On the analysis of region geology ground, we lodge that the formation and evolvement of the basin have consanguineous relation with the evolvement of Tianshan tectonic. Bestriding over Tianshan tectonic belt of different tectonic property and evolvement and Kuluketage causes that its structure and tectonic evolvement are clearly controlled by base tectonic and forms the deep structure character of belt form south to north with a boundary of Yanqi fracture. Northern base of the basin belongs to southern Tianshan tectonic zone, consists of large number of midd- Devonian and Haixi granite and is a passive continent verge depression. The southern base consists of Kuluketage stratum, mainly including foresinian crystal base and notamorphismless stratum of Paleozoic.2.studying on the tectonic conformation in the base, we expound that the main tectonics consist of near E-W extrusion tectonic zone and N-W conversion tectonic zone in basin and tectonic transmutation take on diamond tectonic layout with forming trap from south to north and forming block from East to west. On the basis of comeback analysis of tectonic and combining with regional tectonic background in basin, we can divide evolvement of Yanqi basin in Mesozoic and Cenozoic into three main phases, that is to say weak extension in early and mid-Yanshan, strong extrusion in late Yanshan and forming phase of thrust in Xishan.3.The study on sediment and sequence strata, sediment veneer in Yanqi basin consist of Trias, Jurassic, Tertiary and Qaternary, the Jurassic coal oddment rock system is the main exploited strata. The Jurassic strata can be divided into three sequences of bride rive-delta, meandring rive- shallow lake and lake- delta. Each sequence can be divided into LST, EST and HST wich show the representative sequence-system in the depression in Jurassic.4.The analysis of thermal history and palaeogeothermal in basin shows that the the更多还原