琼东南盆地南部深水区气烟囱地球物理特征及成因分析  

Geophysical characteristics and genetic mechanism of the gas chimney in deepwater area of southern qiongdongnan basin

作　　者：杨涛涛[1] 吕福亮[1] 王彬[1] 范国章[1] 鲁银涛[1] 杨志力[1] 

机构地区：[1]中国石油天然气股份有限公司杭州地质研究院,杭州310023

出　　处：《地球物理学进展》2013年第5期2634-2641,共8页Progress in Geophysics

基　　金：国家重点基础研究发展计划(973计划)课题<南海深水盆地生物礁碳酸盐岩台地成因机理研究>(批准号:2009CB219406);国家重大专项<西沙海域油气地质综合研究及有利勘探区>(批准号:2011ZX05025-004)共同资助

摘　　要：气烟囱是活动热流体作用形成的一种特殊的伴生构造,它不仅能预测油气勘探方向,而且为钻井工程提供技术支持.前人研究表明,包括琼东南盆地在内的南海北部大陆边缘盆地发育气烟囱.本文基于近年来新采集的高分辨率地震资料,详细说明了气烟囱的地球物理响应特征及其成因机制.首先,分析了气烟囱典型的地震反射特征:柱状外形;顶界面为连续强振幅反射,且常出现顶界面增大现象;底界面难以识别;气烟囱内部为弱振幅、弱连续性反射或反射波突然杂乱,反射同相轴下拉.其次,阐述了气烟囱其它几个地球物理特征:由于含气导致气烟囱内部瞬时频率降低、纵波速度降低;气体向上运移破坏了原始沉积地层的连续性导致相干性变差.气烟囱内部的气体若突破其顶界继续向上散逸在接近海底附近出现微洼陷,若气体到达海底则形成麻坑.再次,结合盆地的地质条件,详细分析了本区气烟囱的形成条件:盆地内普遍存在的地层超压为前提条件;厚层泥岩提供物质基础;幕式泄压是重要条件;局部存在的低应力部位为有利发育位置.Gas chimney, a special associated structures produced by flowing thermal fluid, can predict the exploration directions and provide technical supports for the drilling. Based on the previous research of scholars, gas chimneys exist in Qiongdongnan basin and other northern basins of South China Sea. Owing to the high resolution seismic data of latest years, the geophysical response characteristics of the gas chimney were illustrated. Firstly, the typical seismic reflection characteristics of the gas chimney were analyzed in the following aspects： cylindrical appearance, strong continuous reflection of the top interface, frequent enlarging phenomenon of the top surface, the difficulties in identifying the bottom interface, weak reflection in inner gas chimney, weak continuous reflection or sudden disconnected of reflection, and pulling-down of seismic reflection. In addition, the other geophysical characteristics of gas chimney were depicted： instantaneous frequency lessening, velocity decreasing, the initial sedimenlary formation destroyed by up moving of gas, in the inner of gas chimney gas arising upwards and scattering in the seafloor offshore with minisize sag, and pockmarks emerging while the gas arrived the floor. What＇s more, according to the geology condition of this basin, the formation conditions of gas chimney were analyzed in detail including widespread high pressure of formation, thick mudstone providing sources and episodic pressure relief, and favorable area of low stress.

关 键 词：琼东南盆地 气烟囱 地球物理特征 成因机制 

分 类 号：P631[天文地球—地质矿产勘探]