南海北部陆缘深水区构造演化及其资源效应

南海北部陆缘深水区（水深>300m）蕴藏着丰富的资源，我国对深水区的地质研究刚刚起步，但相关领域已成为科研热点。深水油气盆地的构造演化是油气勘探中最重要的基础性研究之一，因此针对我国南海北部陆缘深水区开展构造演化及其资源效应的研究具有重要的理论意义和实际意义。 本文利用钻井和地震资料并结合区域地质资料，重点研究了珠江口盆地深水区的结构和构造演化，取得如下创新性成果：1）首次利用半地堑分析方法系统解剖了研究区的结构、各构造单元发育特征，在此基础上指出五个有利油气运聚带；2）采用回剥法并利用最新资料进行校正，得到了研究区更为可靠的构造沉降曲线，重新划分了裂陷期和裂后期的分界，认为32Ma南海海底扩张之后裂陷作用仍在持续，直到23Ma左右才开始大规模裂后热沉降，并进一步解释了裂陷期延迟的形成机制；3）应用非连续拉张模型计算拉张系数的方程计算了研究区的壳幔拉张系数，指出了深水区地幔相对于地壳的优势伸展作用；首次运用平衡剖面技术重建了研究区的构造发育史，计算了各构造期的拉张率和沉积速率，指出研究区新生代整体呈现持续拉张，拉张系数在1.1-1.24之间；4）精细刻画了水合物钻采区的地质构造特征，建立了该区天然气水合物成藏的概念模式；建立了一套根据地震叠加速度计算流体势的方法，为水合物成藏规律的研究提供了新的思路。

There were abundant resources contained in the deepwater area of the northern margin of the South China Sea (NMSCS). The study on deepwater area just begins in China which has already been the scientific hotspot. Structural evolution of the hydrocarbon-bearing basin is one of the most important basic researches about the hydrocarbon exploration, therefore, it is important for the theory and reality to study the structural evolution and resource effect of the deepwater area of NMSCS. Based on the drilling and seismic data and regional geological document, this study was carried out mainly on the architecture and structural evolution characteristics of the deepwater area of the Pearl River Mouth Basin (PRMB). Innovative results had been achieved as follows. 1) The architecture of study area and the development characteristics of each structural unit were firstly and systematically analyzed with the half-graben analysis method and five favorable hydrocarbon migration zones were pointed on the basis of basin structure study. 2) Calibrated according to the latest data, the more reliable tectonic subsidence curve of the study area was calculated with the back-stripping method. The boundary of the rift and post-rift stages was redefined. The study indicated that the rifting activity still continued after the seafloor spreading of SCS at 32 Ma and culminated at 23 Ma when the large-scale post-rift thermal subsidence started. The formation mechanisms of the rifting prolongation were explained. 3) The stretching factor calculation equation with the discontinuous stretching model was deducted and crust and mantle stretching factor of the study area were calculated respectively. The results demonstrated the preferential mantle lithospheric extension under the deepwater area of PRMB relative to the crust. The structural development history of the study area was rebuilt firstly based on the balance cross-section method, and the stretching ratio and deposition rate were calculated for each structural period. The study area was proved to be stretched continuously during Cenozoic on the whole and the stretching factor was between 1.1 and 1.24. 4) The geological features of the gas hydrate drilling zone were delineated accurately and the conceptual model for the gas hydrate accumulation was postulated; A set of fluid potential calculation method just based on the seismic stack velocity was established, which provided a new clue to study the gas hydrate accumulation law.