济阳坳陷古近系深部储层成岩演化模式

摘要

The diagenetic evolution modes of clastic rocks in deep formation of Paleogene in the main areas of Jiyang sub-basin are researched through thin-section analysis,scan electricity microscope observation,Ro test,and reservoir physical parameters analyses,etc and combining histories of tectonic development.It is recognized that there are six types of diagenetic evolution modes mainly affected by tectonic setting,reservoir pressure and fluid environment in it.There are early moderate-strong overpressure,moderate-strong compaction,cementation and dissolution with the multiple medium diagenetic evolution mode and the diagenetic evolution mode of late moderate-strong overpressure,strong compaction,cementation and strong dissolution with acidic medium on the weak steep slopes or gentle slopes.The strength of reservoir compaction is mainly affected by the formation time of the overpressure and the fluid environments are controlled by different tectonic setting in these cases.There are diagenetic evolution mode of normal pressure or weak overpressure,moderate-strong compaction,cementation and strong dissolution with the acidic thermal fluid and diagenetic evolution mode of weak-moderate overpressure,little strong compaction and cementation and strong dissolution with the acidic thermal fluid in the deep sags.Thermal fluid which enhances the dissolution of acid soluble components is the main influencing factor of these diagenetic evolution modes.There are diagenetic evolution mode of moderate-strong compaction,cementation and weak dissolution with acdic medium and diagenetic evolution mode of strong cementation,weak moderate dissolution with multiple medium in normal pressure condition on the steep slopes.The multiple medium which results from early deposition water,late diagenetic water and mixture of both is the main influencing factor in these cases.It＇s considered that the stratum and buried depth is the primary factor of the diagenetic alteration of the deep formation in Jiyang sub-basin,Paleogene,and the tectonic position is the basic premise of diagenetic pressure and fluid field characteristic.The deep thermal fluid has different effects on reservoir evolution in different fluid fields.Multiple diagenetic environment of acid-alkaline alternating increases the number of secondary porosity and affects vertical distribution of secondary porosity,but preservation rate of the original porosity in multiple diagenetic environment is more than 5% lower than that in acidic diagenetic environment.%运用岩石薄片鉴定、扫描电镜分析、镜质体反射率分析、X—衍射分析和油层物性分析等手段,结合区域油气地质研究成果,以揭示济阳坳陷古近系深部碎屑岩储层的成岩演化模式和物性演化规律为目的开展工作。结果表明,济阳坳陷古近系深部碎屑岩储层主要受其所处构造背景、地层压力和流体环境的影响,发育6种成岩演化模式。弱陡坡/缓坡构造背景条件下发育早期中强超压—中强压实/胶结/溶蚀—多重介质成岩演化模式和晚期中强超压—（较）强压实/胶结/溶蚀—酸性介质成岩演化模式,超压形成的早晚是影响储层压实作用强弱的主要因素,而流体环境的差异与构造背景的差异有关。深洼陷发育弱超压/常压—（中）强压实/胶结—强溶蚀—热液酸性介质成岩演化模式和中弱超压—较强压实/胶结—强溶蚀—热液酸性介质成岩演化模式,热液活动加强了成岩流体对酸溶性组分的溶解,是该类成岩演化模式的主要影响因素。处于陡坡常压条件下的深层碎屑岩发育（中）强压实/胶结—弱溶蚀—热液酸性介质和强胶结—中弱溶蚀—多重介质成岩演化模式,早期沉积水体、后期成岩水体以及两者混合造成的多重介质是其主要影响因素。综合分析认为,层位和埋深是深部储层遭受成岩改造程度强弱的首要控制因素;构造位置是影响成岩压力场和流体场的基本前提;在不同的流体场背景中,深部热液对储层演化会不同影响;酸碱交替的多重成岩环境增加了次生孔隙带发育个数和次生孔隙垂向分布,但原始孔隙度保存率比以酸性介质为主的成岩环境低5%以上。