摘要:
长昌-鹤山凹陷为珠江口盆地珠四坳陷NE-SW走向的凹陷,是珠江口盆地继白云、荔湾深水区油气突破之后的又一个深水战略性勘探区块,目前无钻井,属于勘探新区,因此基础地质研究尤为重要。通过断层解释和地层厚度分析,认为文昌组和恩平组分别对应早期强裂陷阶段和晚期弱裂陷阶段,并识别多种不同级别和类型的构造变换带。以经典层序地层学理论为指导,通过对全区二维地震资料追踪闭合,将长昌-鹤山凹陷文昌组-恩平组划分为2个二级层序和7个三级层序。在三级层序格架内,根据地震相特征结合经典的地震相-沉积相转换关系,重建了研究区沉积充填演化过程。通过平面断层组合分析认为,研究区发育两个级别(Ⅰ级和Ⅱ级)、六种类型(同向未叠覆型、同向叠覆型、同向平行型、同向共线型、对向叠覆型和背向叠覆型)构造变换带。断陷活动的强弱控制着层序和沉积体系的发育,构造变换带、坡折带类型控制着砂体的分布与规模。针对研究区是深水勘探新区,可通过该思路从构造与沉积耦合度高的区域进行有利区带的预测,为低勘探程度深水研究区的油气勘探提供了科学依据。
Abstract:
Changchang-Heshan depression, located in southwest Zhu-IV subbasin of Pearl River Mouth Basin, extends in NE-SW direction. It is an important strategic exploration block after oil and gas exploration breakthrough in Baiyun and Liwan depression in deep water area. Changchang-Heshan depression is a new area to oil and gas exploration and has no wells, so the basic geological research is particularly important. Based on fault interpretation and formation thickness analysis, rift stages and structural characteristics were studied in detail. Wenchang and Enping Formation experienced two successive tectonic stages, which respectively corresponded to intensive rift stage and weak rift stage. A variety of different levels and types of structural transfer zones were identified at the same time. Guided by the theory of classic sequence stratigraphy, Wenchang and Enping Formation were divided into two second-order sequences and seven third-order sequences based on the two-dimensional seismic data. According to the characteristics of the seismic reflection, transfer the classic seismic facies to sedimentary facies within the sequence framework, and then rebuilt the process of sedimentary system evolution in the study area. Classified two levels(Ⅰ and Ⅱ) and six types of structural transfer zones(syntropy non-overlapping, syntropy non-overlapping, syntropy parallel, syntropy collineation, opposite overlapping and back to back overlapping). The degree of the fault activity controlled the sequence evolution and sedimentation system. Furthermore, structural transfer zone and slope break controlled the distribution and scale of sand bodies. The study area is a new region for oil and gas exploration, this method is focused on the close relation between tectonism and sedimentation. Finally, it offers reliable evidence for favourable region exploration and supports a solid scientific evidence for the low degree oil and gas exploration in deep water area.
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