摘要
针对渤海湾盆地辽中凹陷南洼古近系地层超压成因问题,通过对多种地质资料和研究方法综合应用,提出生烃作用是超压形成的主要机制,在局部地区(W-D构造)存在欠压实和生烃作用叠加形成的超压.主要证据如下:(1)测井曲线除W-D构造外,普遍不具备欠压实地层高孔隙度和低密度的典型特征;(2)沉积背景分析由欠压实作用形成超压的顶面深度与实际不符;(3)超压顶面发育在大套泥岩段内部,深度变化范围较大(2200~3100 m),与烃源岩生烃顶面基本一致;(4)地层有效应力和速度及密度关系表明,超压点均落在“卸载”曲线上,为生烃超压的特征;(5)超压段地层现今处于大量生烃阶段,持续为超压形成提供保证;(6)欠压实作用和生烃作用叠加形成的超压,导致了地层的高孔隙度和低密度,也使地层有效应力与地层速度和密度关系曲线表现出“卸载”现象.
This paper deals with the origin of overpressure in the Paleogene strata,in south of Liaozhong depression,Bohai Bay Basin,through comprehensive application and analysis of various geological data and research methods,we suggest that hydrocarbon generation is the main mechanism.In some areas(W-D structure),there is overpressure formed by superposition of disequilibrium and hydrocarbon generation.The main evidences are as follows:(1)Except for W-D structure,logging curves generally do not have typical characteristics of high porosity and low density caused by disequilibrium;(2)The top depth of overpressure formed by disequilibrium in sedimentary background is inconsistent with the reality;(3)The overpressure top develops in the internal large mudstone section,with greatly varying depth range(from 2200-3100 m),and it is basically the same as hydrocarbon generation top of source rocks;(4)The relationship between formation effective stress with velocity and density shows that the overpressure points all fall on the“unloading”curve,and the overpressure characteristics are hydrocarbon generation;(5)The overpressure source rocks are still in large hydrocarbon generation stage,continue to provide guarantee for overpressure formation;(6)Overpressure formed by superimposition of disequilibrium and hydrocarbon generation is characterized by typical formation high porosity and low density,the relationship curves between effective stress and formation velocity and density formations show obvious unloading phenomena.
作者
王冰洁
王德英
郭涛
王鑫
惠冠洲
薛明旺
Wang Bingjie;Wang Deying;Guo Tao;Wang Xin;Hui Guanzhou;Xue Mingwang(CNOOC Tianjin Company,Tianjin 300452,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2024年第5期1832-1843,共12页
Earth Science
基金
国家科技重大专项(No.2016ZX05024-002-006)。
关键词
沉积
生烃作用
欠压实作用
超压成因
辽中凹陷南洼
渤海湾盆地
石油地质
deposition
hydrocarbon generation
disequilibrium
origin of overpressure
the south sag of Liaozhong depression
Bohai Bay basin
petroleum geology
