济阳坳陷不整合结构的发育过程及发育模式

Development process and model of unconformity in Jiyang Depression

济阳坳陷不整合的发育过程大体可分为风化期、剥蚀期和成岩期3个阶段。风化期是不整合结构形成的基础,剥蚀期是不整合结构得以保存的关键时期,成岩期决定着不整合结构的矿物成分及孔渗结构。由于不整合形成的长期性和复杂性,不整合结构的发育主要受沉积间断时间、风化母岩岩性、保存条件和古气候4种因素的控制,结合不整合结构的发育过程和控制因素的分析,将济阳坳陷不整合划分为凸起—陡坡基岩强风化型、缓坡基岩强风化型和古近系—新近系内部母岩弱风化型3种发育模式。凸起—陡坡带不整合面下岩石孔渗性较好,一般形成潜山油气藏;缓坡带一般形成结构比较完整的不整合,易形成不整合超覆和遮挡油气藏;古近系—新近系内部地层不整合风化时间短、程度弱,可作为油气运移的通道。

The unconformity-forming process can be divided into three periods including weathering,denudation and diagenetic period in Jiyang De-pression. The weathered stage was the base,the denudation stage was an important factor for the preservation of unconformity,and the diage-netic stage decided the mineral composition and poroperm structures. Because of the complexity and protracted nature of the development,the evolution and structure of unconformitv were controlled by four factors including the time of depositional break,lithology of weathered mother rock,conservation condition and palaeoclimate. Combined with the analysis of the developing process and controlling fators,three types were recognized:strongly weathered uplift-abrupt basement,strongly weathered gentle basement,weak weathered mother rock in the Tertiary. The poroperm of uplift-abrupt slope zone under unconformity is preferable and favorable for forming buried hill type reservoir;gen-tle slope zone often formed the unconformity with intact structure,it is suitable for unconformity overlapping and screened oil accumulation;the inner unconformitv with short weathering time and weak weathering in Tertiary can be migration pathway of oil and gas.