川西坳陷新场构造带须家河组超压演化与流体的关系  

A study of the coupling relationship between overpressure evolution and formation water of Xujiahe Formation in Xincang structure area, west Sichuan depression

作　　者：黄丽飞 楼章华[1] 陈明玉 朱蓉[1] 王君[1] HUANG Lifei;LOU Zhanghua;CHEN Mingyu;ZHU Rong;WANG Jun(Institute of Ocean Geology and Resource, College of Ocean Geology, Zhejiang University, Zhoushan 310058, Zhejiang, China)

机构地区：[1]浙江大学海洋学院海洋地质与资源研究所,浙江舟山310058

出　　处：《地质通报》2018年第5期954-964,共11页Geological Bulletin of China

基　　金：国家自然科学基金项目<砂岩致密化过程天然气充注-散失的时序关系研究>(批准号:41572110)

摘　　要：沉积盆地超压体系是油气勘探与开发过程中一个不容忽视的问题,不仅影响了地质流体的运移和聚集,更为勘探带来安全隐患。以实测地压和油田水化学数据为基础,对川西坳陷新场构造带须四段和须二段现今地层水矿化度与现今压力系数关系进行比较,结合地层水特征系数和阴阳离子关系,综合前人研究结果,对须四段和须二段压力演化史与地层水演化过程进行分析,考察川西坳陷须家河组超压系统演化与地层水演化的耦合关系。结果表明,须家河组超压发育与地层水具有密切的联系:(1)须家河组储层段压力分布范围较广,在弱超压至超强压之间,须二段属于中超压而须四段属于超高压,平面分布中须二段探测井中矿化度随压力系数增加而减少,须四段则相反;(2)在压实过程中,由于流体排驱受阻导致"欠压实"超压的产生,随着超压的不断积聚,局部出现裂缝,导致地层水更加强烈的混合作用和运移;(3)生烃作用导致自生压力增大,地层水离子水岩作用强烈,造成流体包裹体与现今地层水离子成分分异;(4)构造挤压抬升过程中,须四段裂缝不发育,压力进一步升高,须二段则产生泄压,出现了凝析水和水侵现象,造成须四段和须二段现今地层水特征的差异。Overpressure systems in sedimentary basins not only affect the migration and accumulation of geological fluid but also bring potential hazard for exploration. Formation water salinity, pressure coefficient, characteristic coefficient and ions relationships of the second and fourth member of Xujiahe Formation（T3 X2, T3 X4） in western Sichuan Basin were integrated and utilized to study the coupling relationship between overpressure system and formation water. The results show that the development of overpressure is closely related to the formation water：（1） the formation pressure varies from weak overpressure to super overpressure in Xujiahe Formation. T3 X2 belongs to medium overpressure, while T3 X4 is super overpressure. The fluid salinity of exploration wells in T3 X2 decreases with increments of pressure coefficient, which yields opposite relationship in T3 X4.（2） Fluid expulsion leads to＂undercompaction＂overpressure during compaction, resulting in the occurrence of fractures and pronounced mixture and migration of formation water.（3） The maturation of organic matter results in the increment of pressure and the composition difference between fluid inclusions and formation water due to extensive water-rock reaction.（4） The scarcity of fractures in T3 X4 results in the increment of formation pressure, while the condensate water and water invasion in T3 X2 results from the development of fractures during uplift. Thus, T3 X2 and T3 X4 display nonidentical characteristics of formation water.

关 键 词：川西坳陷 须家河组 超压演化 地层水特征 

分 类 号：P534.51[天文地球—古生物学与地层学] TE12[天文地球—地质学]