【作者】 杨智；

【导师】 何生； 武恒志；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2009， 博士

【摘要】 准噶尔盆地位于新疆北部，面积13．6×10⁴km²，是我国大型叠合含油气盆地之一。研究区位于准噶尔盆地腹部中央坳陷的盆1井西凹陷、东道海子北凹陷和昌吉凹陷，矿权上属于中石化登记的中部4个区块，是准噶尔盆地勘探程度最低但勘探潜力巨大的一个区域。腹部地区地层展布平缓，大型断层不发育，深部目的层段（主要为中下侏罗统砂岩，部分为白垩系底部砂岩）普遍发育成岩后强超压系统，目前已发现的绝大多数油气储量集中分布在超压顶面附近（超压顶界面之上300m至之下100m范围内）的有利油气聚集区内。以准噶尔盆地腹部超压顶面附近油气藏为研究对象，在刻画超压层展布的基础上，分析超压成因和演化过程，详细研究超压顶面附近源岩及油气地球化学特征、油气分布特征、主要储集空间类型及其形成过程，深入分析超压在超压顶面附近油气成藏过程中的作用，总结超压顶面附近油气成藏的机理，将为理解本区及类似强超压生烃型盆地超压顶面附近油气成藏规律和预测有利勘探目标区提供借鉴。论文的主要研究内容和成果认识概括为以下4个方面。1、准噶尔盆地腹部超压响应特征及机理，成因，展布和演化准噶尔盆地腹部普遍发育深层超压系统，实测砂岩超压揭示深度一般在4470-6160m，超压砂岩段主要为侏罗系，剩余压力约为11-57MPa，压力系数为1．24-2．07，实测超压砂岩样品物性多为低-特低孔渗；在超压带，钻井泥浆密度明显增加，泥页岩和砂岩共同具有相对于正常趋势的异常高声波时差、低电阻率和低地震层速度的响应特征，响应的机理是，超压可导致岩石骨架颗粒间有效应力的减小，从而直接引起通过岩石的速度减小，超压地层温度条件下的高压液态水的电离常数可能明显增加而减小地层电阻率；腹部超压很可能是由于侏罗煤系地层的热演化生烃增压与有效封闭层共同作用形成；利用叠加速度谱资料，选用Dix公式计算层速度、Fillippone公式计算地层压力，结果显示各构造单元超压层分布的深度范围不同，盆1井两凹陷较浅（4000-7000m），其次是东道海子北凹陷和昌吉凹陷东部（5000-9000m），昌吉凹陷中部和西部最深（6000-10000m），超压层大多顺层分布，只是在各凹陷边缘以及凹陷内局部有穿层上拱现象，超压顶面分布的层位由北往南、从东到西逐渐变浅，从三叠系顶部过渡到白垩系底部，超压分布层位主要为侏罗系顶部和白垩系底部；侏罗系的超压演化分为两个阶段，早期超压是由于下伏超压仓内超压流体垂向传递到侏罗系而引发的超压，形成于晚侏罗世到早白垩世，之后压力逐渐减小，到古近纪晚期降到接近静水压力水平，而后由于侏罗系源岩逐渐成熟，油气大量生成，有效封隔层形成，压力逐渐增加，现今压力系数可达到1．6-1．9。2、准噶尔盆地腹部超压顶面附近油气藏油气地球化学特征及成藏过程分析（1）研究区主要烃源岩为中下二叠统湖相暗色泥岩，其次为侏罗煤系地层；侏罗煤系源岩样品显示母源性质以陆源高等植物来源为主，形成于湖沼相弱氧化环境，临近成熟阶段。（2）超压顶面附近各区域30个原油及油砂样品，1个天然气样品并结合其它收集到的资料分析显示二叠系与侏罗系来源的油气特点不同，其中原油碳同位素值、Pr/Ph值、三环萜烷含量丰度及分布型式、规则甾烷分布型式、伽马蜡烷指数、是否含有胡萝卜烷和三芳甾烷等是有效的区分指标；多种成熟度参数(MPI1、4，6-/1，4-DMDBT、αααC₂₉S/（S+R）和C₂₉ββ/（αα+ββ）)计算得出原油的R₀值绝大多数介于0．7-1．0%，处于大量生油的成熟阶段，其中二叠系来源的原油的成熟度稍高；天然气组成以侏罗系米源的煤成湿气为主，兼有侏罗-二叠米源的混源气，烷烃气的成熟度较高，大多在0．9-1．0%。（3）各构造单元不同来源的油气分布特点不同。在盆1井西凹陷北部沙窝地地区，超压顶面之上从上往下分别主要为下二叠统佳木河组和风城组原油，超压仓内主要为中二叠统下乌尔禾组原油；盆1井西凹陷南部莫西庄地区，超压顶面之上相对靠上主要为下二叠统风城组原油，靠近超压顶面的则主要为中二叠统下乌尔禾组原油，天然气主要为混源气，超压顶面之下基本上是中二叠统下乌尔禾组原油，天然气为煤成湿气；昌吉凹陷两段北部的征沙村地区，油气分布在超压顶面之下，主要为中二叠统下乌尔禾组原油；昌吉凹陷西段永进地区，超压顶面之上主要为中二叠统下乌尔禾组原油，超压顶面之下主要为中二叠统下乌尔禾组原油和侏罗煤系原油以及二者的混源油，天然气主要为二叠-侏罗源岩的混源气；东道海子北凹陷CH1井和昌吉凹陷东段D字号井区，油气主要集中在超压仓内，均为侏罗煤系原油，D字号井区天然气为侏罗-二叠混源气。（4）源岩热演化模拟显示，下二叠统烃源岩在早二叠世晚期进入生油门限，在晚二叠世进入生油高峰，并很快达到了生气阶段；相比下二叠统源岩，中二叠统源岩的生油区间更宽，从中二叠世晚期可以一直持续到晚白垩世；侏罗煤系源岩在早侏罗世晚期开始进入生烃门限，但各构造单元现今热演化的程度有差异，盆1井西凹陷凹陷目前仍未达到生油高峰，成熟度介于0．7-1．0%，而昌吉凹陷和东道海子北凹陷已达到生油高峰，成熟度介于0．8-1．2%。（5）腹部油气经历了早晚两期油气成藏，而晚期经历了两次大的油气充注（分别为晚A期和晚B期）。早期（J₂-K₁），盆1井西凹陷佳木河组和风城组来源的原油聚集于J₁b及以下有利圈闭，保存较好，而下乌尔禾组开始排烃；昌吉凹陷西段风城组原油已聚集于较高部位的中上侏罗统储层中，破坏严重，稍后下乌尔禾组原油充注，也遭到了中等程度的生物降解。晚A期（K₂-E），盆1井西凹陷J₁b及以下佳木河组和风城组油藏向上部层位调整成藏，而下乌尔禾组原油聚集于J₁b及以下有利圈闭；昌吉凹陷两段下乌尔禾组原油继续充注，向上和向北运移，侏罗煤系开始排烃生气，超压逐渐发育。晚B期（N-Q），盆1井西凹陷，侏罗煤系生成天然气，超压逐渐发育，原有油藏进一步向上部层位及向北调整；昌吉凹陷西段，超压仓内下乌尔禾组原油在超压驱动下向上和向北运移，征沙村地区充注成藏，侏罗煤系继续生烃，近源聚集成藏；东道海子北凹陷和昌吉凹陷东段侏罗煤系开始排烃生气，超压逐渐发育，近源或超压驱动远源聚集油气。3、准噶尔盆地腹部超压顶面附近主要储集空间类型与形成过程分析（1）侏罗系沉积时期，准噶尔盆地总体呈现“盆大水浅，源多坡缓，河长扇短，隆坳相间”的格局。纵向上从J₁b到J₂t，腹部沉积砂体总体上是由4个湖退进积三角洲沉积体系构成；平面上为不同时期不同沉积相带的拼合和叠置，形成了滨浅湖砂泥、三角洲多种水道砂体交织发育，为岩性圈闭的形成和油气输导奠定了基础。（2）单井岩性电性组合特征、古生物资料、粘土矿物资料、地层接触关系等方面的证据显示研究区存在J₂t，说明研究区发育J₂t/J₂x和K/J两期区域性不整合，含有类型丰富的地层型圈闭。（3）中晚侏罗世，由于燕山早期Ⅰ、Ⅱ幕构造运动，盆地腹部曾发育一大型的NE-SW向古隆起即车莫古隆起，经历了初始发育阶段（J₁s）、第一次强隆升阶段（J₂x末期）、相对稳定沉积阶段（J₂t沉积期）、第二次强隆升阶段（J₂t末期）、隐伏埋藏阶段（K-E）和掀斜消亡阶段（N-Q）等6个演化阶段。（4）研究区发育2种5类地层、岩性隐蔽油气藏，即不整合/滩坝砂体地层油气藏、不整合/三角洲平原泥岩/三角洲前缘砂体地层油气藏、不整合/河道砂体地层油气藏、河流三角洲透镜体砂岩岩性油气藏和多砂体叠置拼合非均质隔挡型岩性油气藏。（5）准噶尔盆地腹部超压顶面附近砂岩是流体-岩石频繁交互作用的场所，其中普遍发育的碳酸盐胶结物与超压顶封层形成和次生孔隙带发育带密切相关。①准噶尔盆地腹部超压顶面附近深层砂岩中，碳酸盐胶结物是最主要的胶结成分，普遍发育以晚成岩阶段含铁方解石、含铁白云石或铁白云石胶结为主的、与有机质成熟过程有关的碳酸盐胶结；垂向上超压顶面附近发育有几个次生孔隙带，其中碳酸盐胶结物含量和孔隙度呈互相补偿的关系。②超压顶面附近砂岩中碳酸盐胶结物碳、氧同位素的分布特征可为总结超压顶面附近超压流体流动规律提供如下证据：样品中碳酸盐胶结物碳、氧同位素同时较明显的偏负，砂岩中碳酸盐胶结物碳、氧同位素集中分布在受有机质氧化分解作用影响的有限区域，绝大多数泥岩的碳酸盐碳、氧同位素也分布在这一区域；碳酸盐胶结物氧同位素温度分布和自生碳酸盐胶结物的流体包裹体数据均显示，本区的碳酸盐胶结物主要是晚期热流体活动的产物；超压顶面附近碳、氧同位素具有在超压顶面处δ¹³C和δ¹⁸O为最大值，而向上向下均减小的变化特点，这是超压流体向上部超压顶面附近相对低能环境多期次排放、动力分馏作用的结果。③准噶尔盆地腹部侏罗煤系地层热演化形成的大量油气和酸性物质溶蚀-胶结作用形成的碳酸盐胶结物封隔层，形成了古近纪晚期以来的强烈超压；砂岩储层主要经历了两期次生孔隙生成，早期中晚侏罗世构造抬升导致的大气淡水淋滤溶蚀对现存孔隙贡献不大，而晚期在超压驱动下由有机酸及CO₂向上幕式排放产生了规模较大的溶蚀，由于超压的支撑和保护作用，使该期形成的次生溶孔最具意义。4、准噶尔盆地腹部超压顶面附近油气成藏机理及有利勘探目标预测（1）准噶尔盆地腹部油气主要在超压顶面附近聚集（超压顶界面之上300m至之下100m范围内）。（2）在准噶尔盆地腹部这样的成岩后生烃型强超压盆地中，烃源岩位于超压仓内，超压顶面本身就是一个岩性物性封堵面，也是油气运移的平衡面，源岩的生烃热演化、输导格架的空间构成、超压能量场的演化、超压顶封层的性质以及超压顶面附近有利圈闭的类型和分布，共同控制着超压顶面附近油气成藏的过程和现今油气富集区的分布。（3）与超压演化过程密切联系，准噶尔盆地腹部超压顶面附近侏罗系圈闭经历了早晚两期油气成藏，而晚期经历了两次大的油气充注。（4）准噶尔盆地腹部超压顶面附近有利勘探目标应为超压流体集中排放点附近的有利圈闭和超压仓内近超压顶面的有利圈闭。论文取得的创新点主要体现在以下两个方面：1、提出研究区超压顶面附近存在碳酸盐胶结物发育带，且这些胶结物的组成物质应来自深部的高压热流体，与有机流体物质的迁移有关，碳酸盐胶结物所对应的碳、氧离子具有白超压仓向上部相对低能环境迁移的趋势；2、提出研究区超压顶面上下有限区域内的油气富集主要是晚侏罗-早白垩世以来深部超压仓内的与油气生成增压有关的含烃超压流体通过断层-裂缝输导系统向上部岩性和地层圈闭等储集空间排放、充注和成藏的结果。更多还原

【Abstract】 Covering an area of about 1.36×10⁵ km², the Junggar Basin is located in the northern part of the Xinjiang Uygur Autonomous Region, NW China, which is one of the most prolific oil provinces in China. As both a lowest explorated area and also a more potential area in Junggar Basin, the study area is seated in the West Pen1 Well Depression, North Dongdaohaizi Depression and Changji Depression in the central Junggar Basin. Deep zone overpressure system is commonly developed in central Junggar Basin （deeper than 4000 meters） and many drillings met the overpressure zone. As probably hydrocarbon-originated and post-diagenesis-stage overpressure in central Junggar Basin, oil and gas were mainly accumulated around the top overpressured strata. Studying the reservoirs near the top overpressured surface in central Junggar Basin, based on description of overpressured strata distribution and analysis of overpressure origin and evolution, to research into the chemistry characteristics of coal-bearing source rocks and hydrocarbon, the hydrocarbon distribution characteristics, the main types of reservoirs and its formation processes and so on in detail, will help to better understand the processes of hydrocarbon migration, fluid-rock interaction, secondary porosity formation and hydrocarbon accumulation controlled by such overpressured system. The thesis is divided into four parts as follows.1 The geophysical response characteristics and its mechanisms, origin, distribution and evolution of overpressure in central Junggar BasinThe measured abnormally high pressures of the sandstone layers in central Junggar Basin reveal the depths generally ranging from 4470m to 6160m. The overpressured layers of sandstones are mostly in the Jurassic Formation, only a few sections are in the bottom of the Cretaceous Formation. The excess pressures （formation pressure minus hydrostatic pressure） range from approximately 11 MPa to 57MPa with the pressure coefficients （formation pressure divide by hydrostatic pressure） of 1.24 to 2.07. The measured porosity and permeability for overpressured sandstone samples are mostly lower to very lower.Marked increases of the densities of drilling mud in the fluid overpressured zones are presented, and the responses of exceptionally high sonic and low resistivity logs relative to their normal trends in the overpressured shales and sandstones can be observed. The values of vitrinite reflectance in the large overpressured zones of Jurassic Formation range from about 0.55-1.0%. The observed data suggests that the top of large overpressured zones may not be shallow at depth of 4400m, and the tops in some drilling well are to reach as deep as about 6000m. The depth distributions of large overpressured zones are controlled by the burial depths of the Jurassic Formation （mature source rocks）. This study indicated that the main cause of overpressures in the Jurassic Formation of full compaction is hydrocarbon generation-related. The physical simulation experiments show that the effective stress of rock framework reducing is due to high pore fluid pressures, which can directly lead to the decrease of velocity of acoustic wave through the rocks, that is the higher interval transit times responding to overpressuring rather than to higher porosities. Under the overpressured formation temperatures, the ionization constant of high-pressure liquid water （near-critical water） may be increased, which appear to decrease formation resistivity.The depth of overpressure strata in central Junggar Basin differs in different depressions. The West Pen1 Well Depression has the depth from 4 kilometers to 7 kilometers, and the North Dongdaohaizi Depression and the east part of Changji Depression have the depth from 5 kilometers to 9 kilometers, and the center and west of Changji Depression have the depth from 6 kilometers to 10 kilometers. Most of the overpressure systems were along-bed distributed, and layer penetration could be found in the margin area and some local areas of the depression. Those strata transferred from the top Triassic to the bottom of Cretaceous.The overpressure evolution is divided into two stages. The early stage began Late-Jurassic or Early-Cretaceous generated by the transferred overpressured fluid from bottom overpressured strata, and the overpressure strength gradually declined to hydrostatic pressure in Late-Eogene. After Late-Eogene, the overpressure strength ascended as a result of amounts of hydrocarbon generation when the Jurassic coal-bearing strata maturated, and the pressure coefficient could reach 1.6 to 1.9 present day.2 The geochemistry characteristics of coal-bearing source rocks and hydrocarbon, and the analysis of hydrocarbon accumulation processes near the top overpressured surface in central Junggar BasinThe most important source rocks are the Lower-Permain and the Middle-Permain lacustrine facies mudstones, and the Jurassic coal-bearing mudstone is the secondary important source rocks in central Junggar Basin.Based on the organic geochemistry datum of the 30 crude oil and oil-bearing sandstone samples, 1 natural gas sample, and other collected data, several available index marks differing the hydrocarbon source from the Permain source rocks and the Jurassic source rocks can be summed up, such as crude oil carbon isotopic values, Pr/Ph values, tricyclic diterpane distribution content and their internal distribution types, homosterane distribution types, gammaceran index, if have carrotane and tri-aromatic sterane or not, and et al. The vitrinite reflectance calculated from many maturity indexes, such as MPI1, 4,6-/1,4-DMDBT,αααC₂₉S/（S+R）, C₂₉ββ（αα+ββ）, and so on, is ranging from 0.7% to 1.0%, and is in the maturity stage generating amounts of liquid hydrocarbon, in which the maturity of Permain source rocks is a little higher. The natural gas is mainly comprised of coal-bearing wet gas, and the calculated maturity is mainly between 0.9% and 1.0%.The distributions of different sourcing hydrocarbon in different tectonic units are different. In the central Junggar Basin, the Lower-Permain source rock began to generate hydrocarbon （R_o=0.5%） at about late Early-Permain, reacheed the hydrocarbon generation peak（R_o=1.0%） at about Late-Permain, and quickly came to the high maturity（R_o=1.3%） later; comparing with the Lower-Permain source rock, the time scale of hydrocarbon generation of the Middle-Permain is longer, from late Middle-Permain to the Late-Cretaceous; the Jurassic coal-bearing source rock began to generate hydrocarbon at about late Early-Jurassic, but the maturity values differs each other in different tectonic units at present day, respectively, West Pen1 Well Depression 0.7-1.0%（R_o）, North Dongdaohaizi Depression and Changji Depression 0.8-1.2%（R_o）. It experienced two stages of hydrocarbon accumulation, and there are two times of great hydrocarbon charge in the late stage of hydrocarbon accumulation in the central Junggar Basin. 3 The main types of reservoirs and its formation processes near the top overpressured surface in central Junggar BasinFrom J₁b to J₂t, the sedimentary depositions are comprised of four delta regime prograding sequences.Based on the evidences of the litho-electrical assemblage feature, paleontology, clay minerals, stratigraphic contact relationships in the strata beneath J/K unconformity, it can prove the existence of J₂t in Middle-Che-Mo Palaeo-Uplift in central Junggar Basin, and this fact indicates there are various stratigraphic traps in study area.The Che-Mo Palaeo-Uplift formed in Middle-Late-Jurassic and experienced six evolution stages.Fluid and rock interact frequently in the deep buried sandstones near the top overpressured surface in central Junggar Basin, and commonly distributed carbonate cements record abundant information on the episodic overpressured fluid flow in geo-history. Through characteristics analysis mainly on the carbon-oxygen isotopic in carbonate cements, combined with the reservoir petrography, fluid inclusions, and other data, in deep buried sandstones near the top overpressured surface in central Junggar Basin, several conclusions can be summed up as follows: （1） ferroan sparry carbonate cements formed in Late Diagenesis Stage are the uppermost fillings in the reservoir; （2） co-variation ofδ¹³C andδ¹⁸O of carbonate cements in sandstone are apparently lighter negative values, and are concentrated in finite areas close related with organic influence; （3） carbonate cements are mainly products of thermal fluid movement in Late Diagenesis Stage; （4）regarding the top overpressure as the boundary, the co-variation ofδ¹³C andδ¹⁸O in sandstone carbonate cements are apparently lighter negative values, showing such law as: lighterδ¹³C vs.δ¹⁸O near the coal-bearing Jurassic stratum, heavierδ¹³C vs.δ¹⁸O in the top overpressure, and lighterδ¹³C vs.δ¹⁸O upper the top overpressure, which is considered to be the results of isotopic kinetics fractionation derived from episodic overpressured fluid flow; （5） secondary porosities, dissolved by episodic overpressured acid fluid （organic acid and CO₂） from Lower-Jurassic and Middle-Jurassic coal-bearing stratums, are the most important reservoir space for hydrocarbon accumulation.4 The hydrocarbon accumulation mechanisms and the advantageous exploration target prediction near the top overpressured surface in central Junggar BasinHydrocarbon was mainly accumulated in a narrow areas, 300 metres above and 100 meters below the top overpressured strata in central Junggar Basin .In central Junggar Basin, as a hydrocarbon-originated and post-diagenesis-stage overpressured basin, source rocks are in the overpressured compartment, the top overpressured surface is both a tight-lithostatic and unpermeable seal surface and a balance surface of hydrocarbon migration. The thermal evolution of source rocks, the spatial composition of the transportation pathways, the evolution of the overpressure, the characteristics of the top overpressured seal, and the types and distributions of the advantageous traps and reservoirs, are all the controlling factors of the hydrocarbon accumulation processes and the hydrocarbon accumulated areas distribution near the top overpressured surface in central Junggar Basin. Close related with the evolution of the overpressure, the traps and the reservoirs near the top overpressured surface experienced two stages of hydrocarbon accumulation, and there are two times of great hydrocarbon charge in the late stage of hydrocarbon accumulation in the central Junggar Basin.The traps near the spots where the overpressured organic fluid released are the advantageous exploration targets near the top overpressured surface in central Junggar Basin.更多还原