【作者】 孔敏；

【导师】 石万忠；

【作者基本信息】 中国地质大学 ， 能源地质工程， 2010， 硕士

【摘要】 琼东南盆地是一个典型的高温高压盆地,以超压的研究为切入点,来加深对研究区油气运聚规律的认识,可以为盆地的进一步勘探提供指导依据。目前对于该盆地高压条件下区域性的特别是中央坳陷带的油气运移方向还不是很明确,从而严重制约了对该盆地油气运聚规律和有利勘探区带的整体认识。本文以超压盆地特殊的油气运移动力机制为研究目标,运用油气成藏动力学、沉积学、地球物理学等学科知识,在钻井、岩性、测井、速度谱、地震等资料的基础上,通过速度谱资料的读取及运用相关的地震资料、单井资料在相关软件中进行研究区超压建模,在地震剖面上进行流体活动信息识别与分类,对研究区的各种模拟参数进行精确指定,在盆地模拟软件中完成古压力及油气运移演化过程的模拟,最终综合多种信息对研究区开展有利目标区初步预测。本研究的主要成果与结论包括以下几点：(1)现今超压压力特征琼东南盆地普遍发育超压,从单井上能识别的超压类型有两种,一种是双层超压结构一种是单层超压结构,其中双层超压分布范围比较小,仅限于临近莺歌海盆地的崖城21-1与崖城19-2构造附近,而其他位置均为单层自生超压。研究区北部隆起带局部发育超压,远离中央坳陷带的位置压力系数较小,靠近中央坳陷带的位置,受凹陷的强超压影响,压力系数较大,从西向东,相同的埋深压力系数有逐渐变小的趋势。中央坳陷带内普遍发育超压,且压力系数最大,随着地层的加深,压力系数不断增大,但一些坳陷内低凸起及断层附近由于泄压作用,压力系数相对较小。南部隆起区的压力是最小的,除了一些较深的小断陷发育超压外,其它地区基本都不发育超压或发育弱超压。(2)流体活动信息的分类、特征及对油气运移的指示意义琼东南盆地地震剖面上可识别出多种流体活动,主要包括亮点、泥—流体底辟、海底麻坑、油气泄漏通道、岩浆底辟及杂乱带等。其中亮点主要发育在新近系浅层,分布在北部隆起带,受2号断层控制,中央坳陷带及南部隆起区亮点较少,主要受底辟构造控制,西部亮点分布较广相对分散,而东部亮点则集中分布于松涛凸起的东段、宝岛凹陷及长昌凹陷。流体活动在地震剖面上一般不单独出现,而是以组合的形式出现,主要的组合类型有三种,底辟+底辟裂缝+亮点的组合、油气泄漏通道+亮点的组合以及底辟+底辟断层的组合,前两种可以作为油气的有效通道,对油气聚集具有积极的指示意义,而缺乏亮点的组合形式则对油气运聚一般起消极作用。(3)压力演化特征从单井一维模拟的结果来看现今钻井钻遇的超压从梅山组沉积时就开始形成,但在梅山组晚期随着构造抬升有局部的泄压,黄流组和莺歌海组是现今超压的主要形成期,琼东南盆地超压的主要成因机制应为欠压实成因。从各凹陷的压力演化曲线图上可以看出,西部地区的乐东凹陷及陵水凹陷一直保持着较强的压力,崖南凹陷压力相对较小,基本处于常压状态；松南凹陷及宝岛凹陷也发育超压但晚期压力系数相对较低；长昌凹陷早期压力较高,晚期压力趋于常压。5.5Ma之前,东西部的超压中心是分开的,西部超压中心为乐东—陵水凹陷,东部超压中心为长昌凹陷,中间的松南凹陷仅发育弱超压,5.5Ma以后,超压中心开始转移到盆地西部,整体压力系数增大,形成了以乐东凹陷为超压中心的压力展布格局。(4)油气运移特征从二维模拟的剖面图上可以看出该盆地生烃能力较强,15.5Ma之前油气生成量较少,之后油气生成量增加,尤其是5.5Ma以后,油气运移强度明显增大,油气运移以垂向运移为主,断层两侧的油气运移到达的顶界面比周围较浅,说明断层是研究区主要的油气运移通道。根据模拟结果可知油气运移有以下几个主要特征：油气主要沿断裂输导,尤其是控盆的主断裂；侧向油气运移特征不明显；油气在中央坳陷带内生成,运移指向南北隆起带地势相对较高的构造圈闭。(5)有利的油气目标区预测结合平面压力展布特征及油气运移模拟的结果可知,从油气运移的角度来说,有利的油气聚集区主要集中有输导断层且连接生烃凹陷、泄压带(或常压带)、流体势较低的位置,具体到研究区内就是低压低势的北部隆起带的环崖南凹陷地区、宝岛—松涛地区以及南部隆起带。然而油气运移的指向区不一定就会成为有利的勘探目标区,本研究又重点从泥岩厚度特征及流体活动信息等多方面对研究区的封盖条件进行了评价,结果显示南部隆起带的低凸起位置及中央坳陷带与北部隆起带的交界处盖层条件都比较差,北部隆起带的盖层条件较好。同时综合北部物源丰富砂体较发育且凹陷内生烃能力较强的有利的油气成藏条件,最终初步预测研究区内有利的目标区主要是两个即环崖南凹陷地区以及宝岛—松涛北部地区。本研究的主要创新点有以下两点：(1)基于地球物理手段,对地震剖面上可以反映油气运移与散失的流体活动信息(包括亮点、泥-流体底辟、油气泄漏通道、底辟断层、多边形断层等信息)进行了识别、解释与分类,并综合上述信息开展了对研究区油气运移特征的直观分析；(2)利用速度谱资料建立了琼东南盆地全区内(包括深水区)的超压模型,利用盆地模拟的技术与手段对研究区尤其是深水区压力演化特征及油气运移过程进行了定量模拟,此成果对认识全区(尤其是深水区)内的超压展布、油气运移特征具有重要的意义。更多还原

【Abstract】 Qiongdongnan basin is a typical basin of high temperature and high pressure. Using the overpressure as the study point to deepen the cognition of hydrocarbon migration and accumulation can provide criterion for further exploration of the basin. Now the hydrocarbon migration direction in the study area is not very clear, which restricts to understand the hydrocarbon migration and accumulation and the favorable exploration zones. Under the guidance of hydrocarbon accumulation dynamics, sedimentology and geophysics, this paper is mainly to study the special hydrocarbon migration dynamic mechanism of the basin based on the data of drilling, lithology, well logging, velocity spectrum and seismic data. The processes include building overpressure model using velocity spectrum, seismic data and drilling data, identifying and sorting the fluid activities information in the seismic profile, simulating the evolution process of the paleopressure and hydrocarbon migration and finally forecasting the favorable zone in the study area.The research results and conclusions include the following fields:(1) Current overpressure characteristicsQiongdongnan basin exists overpressure commonly. There are two overpressure types, double overpressure structure which only exists in Yc21-1 and Yc 19-2 structure near the Yinggehai basin and single overpressure structure which exists other areas in Qiongdongnan basin.In the north uplift zone of the study area, there exists overpressure partially. If it is farther from the central depression area, the pressure coefficient will be lower, while the pressure coefficient becomes lower from west to east in the same burial depth. In the central depression area, the overpressure is common while the pressure coefficient is very high, the deeper the higher, unless in some lower uplifts and the area near the faults. The southern uplift pressure is the smallest where generally don’t develop overpressure or only develop weak overpressure, except in some deep small fault depression,(2) The flow activities information’s classification, of characteristics and the significance to hydrocarbon migration.Various fluid activities can be identified on the seismic profiles in Qiongdongnan basin which include bright spot, mud-fluid diapir, seabed pockmark, gas leakage path, magma diapir and disorderly reflection zone etc. the bright spots mainly occur in neogene shallow layer, mainly distribute in north area controlled by No.2 fault while in the central depression area and the south uplift area the bright spots are less which are controlled by diapir or overpressure. In the west, the bright spots are dispersive while in the east they are mainly concentrated in the east of Songtao uplift, Baodao sag and Changchang sag. Generally, on the seismic profile, the fluid activities appear not separately but in the form of combination. There are three types of combination, diapir+diapiric cracks+bright spots, the gas leakage path+bright spots and diapir+ diapiric cracks. The former two combinations can be effective hydrocarbon migration channels and positive indicator to hydrocarbon migration and accumulation, while the last combination generally is negative indicator because it lacks of bright spots.(3) The evolution characters of overpressureThe simulation results of the single well show that the overpressure formed from the Meishan formation depositional stage and massively generate in Huangliu and Yinggehai formation stage. The main overpressure genesis mechanism is under compaction. In the pressure evolution graph, Ledong sag and Lingshui sag maintain strong pressure all the time, Ya’nan sag has not overpressure, Songnan and Baodao sag also develop overpressure but not strong as Ledong and Lingshui sag, Changchang sag had high pressure in the early time but low in the late time. Before 5.5Ma, the overpressure centers of the west and east were separate, Longdong-Lingshui sag in west while Changchang sag in east; after 5.5Ma, the center transferred to the west, forming the pressure distribution patter by LeDong sag as overpressure center.(4) The characteristics of hydrocarbon migrationIn the section of 2D simulation, we can see that the basin have strong ability to generate hydrocarbon. Before 15.5 Ma, the oil formation was small, and then oil formation increased, especially after 5.5 Ma, the intensity of hydrocarbon migration increased. The hydrocarbon migration is mainly vertical migration while the interfaces of hydrocarbon migration arrived in the both sides of faults are shallower than the around area which implies that fault zone is the main research of hydrocarbon migration channels. According to the simulation results, we can see that the hydrocarbon migration have the following main characteristic:oil transport is conducted the faults, especially the main fault which controls the basin’s sedimentary; the lateral hydrocarbon migration is not evident; hydrocarbon mainly generates in the central depression and migrates to the relatively high hypsography traps in the north and south.(5) Forecasting of the favorable exploration zoneWith the pressure distribution and hydrocarbon migration simulation results, we know that from the perspective of oil and gas migration, the favorable hydrocarbon accumulation zones are the areas near the faults, with low pressure and low fluid potential such as Yacheng area, Badao-Songtao area and the uplifts in south. However, the favorable hydrocarbon accumulation zones not always are the favorable exploration zone, the sealing condition must be considered. After the analysis to the mudstone thickness and fluid activities information in the study area, we know that only the north has the good sealing condition, other areas are all poor. So at last, the areas according Ya’nan sag and north of Baodao-Songtao area are forecasted as the favorable exploration zones.The major innovations are as follows:(1) Using geophysical methods, this paper identified, interpreted and classified the fluid activities (such as bright spot, mud-fluid diapir, gas leakage path, diapir crack, polygon fault and so on) on the seismic profile and then analyzed the hydrocarbon migration characters based on all the information.(2) This paper built the overpressure model of Qiongdongnan basin (deep water area included) using the velocity spectrum data, simulated the overpressure evolution characters and hydrocarbon migration process in the entire basin. The job is very significant for understanding the overpressure distribution and hydrocarbon migration characters of the study area especially the deep water area.更多还原