珠江口盆地白云凹陷底辟构造类型及其成因

Diapir Structure and Its Origin in the Baiyun Depression,Pearl River Mouth Basin,China

珠江口盆地位于中国南海北部,是中国近海含油气盆地中一个重要的盆地.盆地内发育众多形态各异的底辟构造,目前仅有少量的文章对其进行过分类研究,缺少系统地论述.底辟构造是流体穿层流动的一种特殊形式,对其展开分类及成因分析有助于洞察白云凹陷内流体的活动信息和油气运移特征.本文针对珠江口盆地白云凹陷地震剖面上所显示的大量而且种类丰富的底辟构造,开展了底辟构造识别、分类及其内涵流体活动信息的研究,依据盆地模拟结果和区域构造特征讨论了底辟构造的成因特征,得出如下两个结论:(1)珠江口盆地发育多种类型的底辟构造,有底辟初期的龟背上拱、泥底辟、气体泄流通道、裂缝带这4种类型,不同的底辟构造类型内涵有不同的地质信息;(2)底辟构造的成因与构造活动密切相关,超压对底辟构造的形成与活动影响较小,不起主要的作用.

As one of the most important offshore basins in China, there exist many different kinds of fluid diapirs in the Pearl River Mouth basin, which have been introduced in some papers. However, the systemic study of these diapirs is still to be expected on its classification and origin, which can understand fluid migration better. Fluid diapir structure is a special style of fluid migrating upwards. The aim of this paper is to identify and classify the fluid diapir structure, to analyze the messages implied by the fluid diapir structure, to find out a new method of evaluating the fluid diapir structure characterized by the blank seismic reflection, and to discuss the origin of the diapirs according to basin modeling and structure analysis. On the basis of the investigation, we can come to the following conclusions： （1） There are four kinds of diapirs in the Pearl River Mouth basin including the turtleback-like arch, mud diapir, gas seepage, fault （or crack）, which indicate different geological messages; （2） Structure activity rather than the overpressure is the primary driving pressure on diapirs.