缅甸若开海域气烟囱特征与油气成藏浅析

Features of Gas Chimney and Hydrocarbon Accumulation in Rakhine,Myanmar

李东 范国章 杨志力 鲁银涛 丁梁波

LI Dong FAN Guozhang YANG Zhili LU Yintao DING Liangbo

中国石油杭州地质研究院, 浙江杭州 310023

Hangzhou Institute of Petroleum Geology, Hangzhou 310023, China

以海洋深水高分辨率地震资料为基础，结合地震属性、反演、相干时间切片等地球物理技术识别出典型气烟囱结构，在纵向上从下至上依次可以分为根部、过路区、顶部三个组成单元并存在相应的地震异常特征。若开海域的气烟囱一般是两种模式分布，（1）与断裂带相伴生，主要位于低应力区的断层下盘，（2）与下部地层的异常高压相关，构造上地层容易破裂的区域是气烟囱发育潜在区，这两类气烟囱均与超压和地层破裂相关，属于典型的超压—断裂渗涌型气烟囱。缅甸若开海域与气烟囱有关的油气成藏模式可以分为两类，一类是气烟囱与断层相伴生，油气沿着断裂垂向或者沿着砂体侧向运移，在浅部储层中成藏；另一类是气烟囱不与断层相伴生，气烟囱根部地层中的烃源岩生烃产生的压力超过上覆地层的破裂压力时就刺穿地层垂直向上运移，在浅层遇到以泥质充填物为主的大型峡谷封堵时，就在气烟囱两翼储层中聚集成藏，储层顶部的厚层泥岩作为主要盖层，含有泥质充填物的大型峡谷作为侧向封堵盖层。

High resolution seismic data,combined with geophysical techniques including seismic attributes,inversion,time slice of coherence,can be used to identify the typical gas chimney in the deep sea area.The gas chimney consists of root,crossing area and spire,and with corresponding seismic anomalies.In Rakhine sea area the gas chimneys generally are distributed in two modes.(1) Accompanied by the fault and located in the footwall with low stress areas;(2) Associated with abnormally high pressure in the lower part of the formation and located in the structure with easily broken layer.Both of these two types of chimneys are associated with the overpressure and the fracture of stratum and belong to the overpressure-fault-seepage.There are two hydrocarbon accumulation modes related with the gas chimney in Rakhine,Myanmar.The first is that the oil/gas migrated vertically or laterally along the fault and accumulated in the shallow reservoirs,the other is that the oil/gas in the source rocks spired the overburden layer when its pressure broken the formation fracture pressure of the overburden layer and migrated vertically along the split channel until sealed by the mud-filled canyon and accumulated in the reservoirs of gas chimney’s wing where the thick mudstone on the top of the reservoir acts as the main seal and the mud-filled canyon as the lateral seal.

https://doi.org/10.3969/j.issn.1008-2336.2017.02.033