南海北部潮汕坳陷上白垩统盆地原型及其大地构造背景分析

潮汕坳陷MZ-1井揭示的中生界为深入分析南海北部晚中生代的构造演化提供了关键性的资料.基于MZ-1井的标定,开展了系统的地震剖面构造-地层解释,在中生代地层内识别出Tm30区域性不整合面,同位素定年确定该界面发育于早白垩世末至晚白垩世初,落实了潮汕坳陷上白垩统的分布.此外,在研究区西南部识别出大型的兴宁—东沙逆冲推覆带,主要由多条NW—SE向延伸、西倾的叠瓦状逆冲断层及其伴生的不对称褶皱组成,其明显控制了上白垩统厚度分布.由此可见,上白垩统构造层不具有张裂盆地的典型特征,因此南海北部主动陆缘向被动陆缘的转换不会早于晚白垩世末.研究认为,在南海地区特提斯残留洋盆关闭的总背景下,在约80 Ma时期,南海地块与华南陆块强烈碰撞挤压,在靠近碰撞带处的礼乐滩、潮汕坳陷西南部形成褶皱冲断构造体系,进而控制了潮汕坳陷晚白垩世周缘前陆盆地的发育.

     

潮汕坳陷地球物理特征及油气勘探潜力

潮汕坳陷位于珠江口盆地南部,是珠江口盆地油气勘探的新领域.中生界地层特征和油气勘探潜力是目前工作重点.本文分析了潮汕坳陷区域重力、磁异常特征及地震地质规律,提出潮汕坳陷是衔接东沙群岛和西沙群岛两个构造单元的构造过渡带的观点,同时盆倾断层控制了中生界发育与分布.根据潮汕坳陷地震等地球物理特征及地质规律,结合前人研究结果,分析了该区的油气勘探潜力.     

穿越东沙隆起和潮汕坳陷的OBS广角地震剖面

为了探明南海中北部陆缘深部地壳结构,使用2D射线追踪正演和反演方法,拟合了一条南海中北部陆缘的OBS广角地震剖面(OBS2006-3).该剖面穿越东沙隆起和潮汕坳陷,长319 km,NNW-SSE走向,共投放海底地震仪14台.速度结构模型表明:潮汕坳陷存在巨厚的中生代沉积,最大厚度达到8 km,速度从顶部的4.4 km/s向下增加到底部的5.3 km/s.莫霍面埋藏深度由陆向海方向减小,其埋深从东沙隆起下方的24~25 km减小到南部隆起带的17 km.东沙隆起下方的上地壳中存在一向上突起的高速异常,速度达到6.9 km/s,可能与地幔物质上涌和岩浆活动有关.在整个剖面的下地壳底部存在厚3~12 km,速度为7.1~7.4 km/s的高速层.根据各个时期岩浆活动特征,推测下地壳高速层是由海底扩张停止之后的岩浆底侵作用形成的.     

高分辨率AVO反演技术研究

AVO技术可以得到描述地下介质的多方面信息,这对油气勘探具有非常重要意义.但在实际应用中,子波干涉和上覆层影响等因素使常规AVO技术的效果受到很大影响.本文利用积分法求取AVA道集、引入子波和反演手段来消除上述因素的影响,提高了AVO分析的分辨率.因而,使AVO分析技术用于薄层地质现象研究成为可能.     

综合地球物理勘探在桂中坳陷页岩气资源潜力调查中的应用研究

在多年的(非)常规油气勘探工作中,地震法一直是无可取代的技术手段之一,但对于类似广西地质条件复杂、地形条件恶劣的地区难以采集到高质量的地震资料,重磁电等非震方法技术则能够发挥重要作用.多年以来,在桂中坳陷针对页岩气开展的地球物理勘探工作程度很低,笔者以来宾地区较系统的重磁电工作为基础,通过联合反演与综合研究,有效减小了物探多解性、提高了推断解释的准确度和可靠性,系统查明了研究区中富有机质泥页岩目标层系的分布、埋深及厚度等特征,利用"厚深比"参数对研究区页岩气有利目标区带进行了圈定预测,为桂中坳陷地区下一步的页岩气资源潜力调查和优选靶区等工作提供了重要的基础和指导.     

非线性AVO反演方法研究

与叠后地震数据相比,叠前地震数据包含有更多的反映地下地层特征的信息,利用AVO(Amplitude Versus Offset,振幅随偏移距的变化)信息通过求解Zoeppritz方程的近似公式,叠前反演可直接得到反映地下岩石特征的弹性参数——密度、纵波速度和横波速度.从本质上讲,叠前地震反演是非线性的,但目前多采用线性近似方法求解,降低了地震反演的精度.本文研究基于Aki-Richards近似公式的非线性叠前反演方法,分析了引起弹性参数非线性反演误差的因素,提出了反向加权系数的方法以均衡各反演参数的系数所引起的响应差异,并把具有较强的非线性搜索能力、能够更好地求取全局最优解的量子蒙特卡罗方法引入到叠前三参数非线性反演,改善了叠前反演的精度.理论和实例试算表明:该方法计算精度较高、稳定性较好.     

AVO属性分析方法的改进及其在煤系地层中的应用

在进行AVO属性分析时,直接应用梯度和截距属性做交会图,往往无法将异常与背景趋势有效的分离开.特别在煤系发育的地层中,由于其顶、底界面通常为良好的波阻抗界面,会形成较强的反射波,从而掩盖周围地层的异常信息.基于以上原因,煤系地层中异常信息的分类提取,尤其是煤层气的识别方法一直备受关注.本文对一项AVO截距斜率交会图技术进行了改进,并深入分析了此方法在煤系地层中的应用.最终本文给出了所选区块不同类型异常的分类方法,并进行了实际验证,结果表明该方法用于异常反演有很好的效果.     

多波时移地震AVO反演研究

数值模拟了油藏含油饱和度与有效压力变化时移地震AVO的响应,确定利用时移地震AVO区分油藏参数的变化、实现油藏定量解释的可行性.从Aki等 AVO近似方程出发,详细推导了P_P波和P_S转换波时移地震AVO计算公式.结合岩石物理近似关系和本文推导的时移地震AVO计算公式,推导了利用多波时移地震AVO反演油藏含油饱和度和压力变化的方程.数据试验表明,文中推导的多波时移地震AVO方程能较好地反演油藏含油饱和度变化和有效压力变化,实现油藏定量解释.     

基于逆算子估计的AVO反演方法研究

传统反演算法以优化算法为主,而基于逆算子估计的AVO反演算法则利用了直接求逆的思路.算法的关键在于寻找存在逆函数的子域,进而可以在子域内直接求逆,这种解决反问题的思路不同于一般的优化类算法所采用的直接搜索解的方式,具有更高的效率.AVO反演利用了振幅随着偏移距的变化特征,反演的精度受到地震资料质量的影响,通过加入L1范数约束以及合理的初始模型有助于提高反演的稳定性以及准确度.模型测算和实际应用表明,基于逆算子估计的AVO反演方法具有较高的精确程度和可靠性.     

转换波AVO近似及其在PP/PS联合反演中的应用(英文)

多分量勘探相比常规纵波勘探而言有许多的优势,PP/PS联合AVO分析和反演是强而有效的储层识别方法。在本文中,我们推导了更精确的转换波AVO反射系数公式;并在入射角小于30度时进行了进一步简化,其对于转换波AVO分析和反演而言更加简单有效。基于该近似,我们进行了PP/PS联合AVO反演。实际资料的实例表明,反演得到的纵横波速度比可很好地识别岩性及油气。反演得到的流体因子和泊松比等其他属性在储层处也显示出明显异常,效果显著。     

TTI介质各向异性参数多波反演与PS波AVO分析

把遗传算法引入到了TTI介质AVO信息反演各向异性参数的过程中,依据TTI介质PP波、PS波反射系数公式,建立Thomsen参数和TTI介质对称轴倾角、方位角的目标函数,分别通过PP波和PS波的反射系数反演出了各向异性参数和对称轴倾角、方位角等信息.文中对反演结果的精确度和稳定性进行了分析,发现PS波的反演结果优于PP波反演结果;对称轴倾角的反演准确性明显优于对称轴方位角.本文通过模型正演合理解释了这一现象的原因.最后,本文通过对PS波AVO梯度的研究,提出了利用PS波振幅定性分析TTI介质对称轴倾角的方法.     

综合地球物理方法对南海西北部-印支半岛地区中生界分布的研究

南海西北部是我国海洋油气的重要基地.为了研究该区前新生代尤其是中生代油气资源潜力,本文以岩石物性的差异为基础,建立地质界面与物性界面的联系,利用综合地球物理方法来分析目标物性界面的分布特征.在地震资料控制浅层沉积结构的约束下,根据重力资料,通过小波分析位场剥离等方法得到剩余场,由Parker界面反演法反演计算了研究区的重力基底,结合新生代沉积分布得出中生界分布特征并给出了中生代残留盆地的可能分布范围,为分析研究区中生代油气资源潜力提供参考.     

Time range of Mesozoic tectonic regime inversion in eastern North China Block

An important tectonic inversion took place in eastern North China Block(NCB) during Mesozoic, which caused a great lithosphere thinning, reconstruction of basin-range series, powerful interaction between mantle and crust, a vast granitic intrusion and volcanism, and large-scale metallogenic explosion. The time range of the Mesozoic tectonic regime inversion in the eastern North China Block is one of the key issues to understand mechanism of tectonic regime inversion. Our updated results for recognizing the time range are mainly obtained from the following aspects: structural analyses along northern and southern margins of the NCB and within the NCB for revealing tectonic inversion from compression to extension and structural striking from -EW to NNE; geothermic analyses of the eastern sedimental basins for a great change of thermal history and regime; basin analysis for basin inversion from compression to extension and basin migration from -EW to NNE; petrological and geochemical studies of volcanic roc     

Application of AVO analysis to gas hydrates identification in the northern slope of the South China Sea

Amplitude versus offset (AVO) analysis is a conventional seismic exploration technique in geophysical and lithological interpretation and has been widely used in onshore and offshore exploration. Its use in marine gas hydrate research, however, is still in initial stages. In this study, AVO analysis is applied to seismic profiles at drilling sites where hydrate samples have been recovered. The AVO responses of free gas, bottom simulating reflector (BSRs), and gas hydrates are discussed, and the AVO attributes in relation to gas hydrates are summarized. The results show that changes in intercept, gradient, fluid factor and Poisson’s ratio clearly reflect: (i) location of free gas and the BSR, and (ii) spatial relations between blank zone, BSR, gas hydrate, and free gas.     

井震联合分析预测神狐海域天然气水合物可能的垂向分布

已有的地质与地球物理信息表明南中国海北部陆坡神狐海域存在天然气水合物,2007年钻井和取样结果证实其以细颗粒均匀存在于水合物稳定带内,但区域分布范围极不规则.由于测井记录长度和取样深度的范围有限,天然气水合物垂向分布特征难以确定.为了深入了解此区域天然气水合物深度上的分布规律,对SH7井的多种测井数据进行综合分析并与地震反射特征建立联系,得到三个主要的沉积物性变化层位并以此为基础进行叠后数据的伪井约束反演,结果表明在已证实的含水合物层之下还存在高速层.而AVO叠前正演模拟分析结果与实际地震数据对比表明,研究区的天然气水合物稳定带可能由含水合物沉积物与饱水沉积物的薄互层组成,这就意味着在取样获得天然气水合物样品的深度之下,很可能存在另一个含水合物层.     

南海北缘东沙隆起中生代以来的埋藏史和热史重建——来自LF35-1-1井(U-Th)/He和Ro的证据

沉积盆地埋藏史和热历史重建是了解盆地成因和油气形成条件的重要依据,而目前利用古温标手段研究珠江口盆地内东沙隆起热史和埋藏史的成果寥寥无几.本研究中,我们基于磷灰石与锆石(U-Th)/He年龄的反演结果给出了更多合理的约束条件,在此基础上对同一套镜质体反射率Ro数据进行了古热流法模拟计算,获得了钻井自中生代以来的地层温度史.反演结果显示LF35-1-1井区在早始新世-早渐新世发生了一期强烈的抬升剥蚀,地层剥蚀量为2000 m左右.拟合获得的埋藏史和热流史显示该井区在早始新世(~55Ma)经历了最高井底古热流(100 mW·m~(-2)),之后热流减小,持续至现今64.3 mW·m~(-2).最高古地温与隆升剥蚀在时间上的耦合体现了抬升事件对地温冷却的影响,但不足以排除基底热流下降因素.本次研究首次将(U-Th)/He技术用于南海北缘深水区盆地的热史研究,获得的热史结果更加符合现有的构造沉积大地构造方面的认识,展示了利用多种古温标手段进行盆地精细热史研究的良好效用.     

Rifting and basin inversion in the eastern margin of the Japan Sea

Abstract Extensional basin formation and subsequent basin inversion in the southern area of the eastern margin of the Japan Sea were studied on the basis of the interpretation of seismic profiles (total length approximately 15 000 km) and the fossil analyses of 77 sea-bottom samples. Rift (Early to Early Middle Miocene), post-rift (Middle to Late Miocene), pre-inversion (Late Miocene to Pliocene) and inversion stages (Pliocene to Quaternary) were differentiated by the extension and contraction of the crust. Many small-scale rifts were formed in the Sado Ridge and the Mogami Trough during the rift stage, simultaneous with back-are spreading of the Japan Sea. Most of the rifts were east- or southeast-facing, rotational half-grabens bounded by west-dipping normal faults at their eastern boundaries. The syn-rift sequence can be divided into lower and upper units by an erosional surface. The sequences are presumed to be composed mainly of fining-upward sediments. The trend of most rifts is north-northeast with the remainder being of east-northeast-bias. The north-northeast trending rifts are distributed widely in the Sado Ridge and Mogami Trough and do not show an en échelon arrangement, suggesting that they were formed mainly by pure extension nearly perpendicular to the arc. The east-northeast trending rifts are presumed to have been developed by a north-northwest extension in the late rift stage, which may have accompanied a right-lateral movement in the eastern margin of the Japan Sea. During the post-rift stage, the rifts and adjacent horsts subsided and became covered by the post-rift sequence, characterized by parallel and continuous reflections. This suggested no significant tectonic movements in this period. In the pre-inversion stage many of the rifts subsided again, presumably because of down-warping due to weak compressional stress. The normal faults reactivated as reverse faults during the inversion stage due to an increase in compressional stress. Many of the rifts have been uplifted and transformed into east-vergent asymmetric anticlines. The basin inversion is greatest in the Sado Ridges and in the Dewa Bank Chain, while it is least developed in the Mogami Trough and in the western slope of the Sado Ridge, in which some normal faults have not been reactivated. The increase and decrease of the inversion corresponds to the peak and trough of undulation at an interval of about 50 km trending parallel to the arc.     

南海含天然气水合物地层地震反射特征及可能分布研究

天然气水合物是当前能源与环境领域的研究热点之一,南中国海是天然气水合物赋存的有利区域。天然气水合物的存在改变了沉积地层的声学特征,这一性质使多道地震勘探成为发现海洋天然气水合物的主要手段。本文首先根据地震成像结果定性分析南海可能含天然气水合物沉积地层的地震反射特征,初步确定天然气水合物存在的可能性并指出地震成像关键技术。在无井条件下,构建虚拟井进行波阻抗反演得到定量的地层速度参数进一步证实这一可能性,最后将反演获得的速度场与ODP184 航次在此区域获得的地球物理、地球化学信息综合分析,可以确定此区域天然气水合物的存在及其空间展布。     

Fission-track-age records of the Mesozoic tectonic-events in the southwest margin of the Ordos Basin, China

Based on the analysis of apatite and zircon fission track (FT), the FT age distribution and the peck-ages of the Mesozoic tectonic events in the southwest margin of the Ordos Basin (OB) were discussed. (1) The early event mainly occurred at 213-194 Ma with a peck-age of 205 Ma, and corresponded to the tectonic uplift and the mega-clastic deposit in the southwest OB during the Late Triassic. (2) The middle event included at least two episodes. One was at 165-141 Ma with a peck-age of 150 Ma, and the other was at 115-113 Ma with a peck-age of 114 Ma, corresponding to the over-thrusting and the mega- clastic deposits in the southwest OB during the Late Jurassic to the Early Cretaceous. (3) The late event mainly demonstrated the regional uplifting and included at least two episodes. One was at 100-81 Ma with a peck-age of 90 Ma, and the other was at 66-59 Ma with a peck-age of 63 Ma. Additionally, the relationship analysis of the tectonic event and the mineralizing chronology revealed that the extreme environment of the peck-age event and the subsequent moderate activity could be the key factors of the multiple resources coupling and coexistence in the OB.