酒东坳陷营尔凹陷下白垩统储层孔隙特征及其影响因素研究

Characteristics of Pore Evolution and Its Controls of Lower Cretaceous Reservoir in Ying'er Depression,Jiudong Basin

酒东坳陷营尔凹陷油气储层以低孔、低渗和特低孔、特低渗为特征,储层物性差严重制约着该区油气的勘探和开发。本文通过岩石薄片、铸体薄片、荧光薄片、X衍射、扫描电镜和压汞分析等手段对该区孔隙特征及影响因素进行了研究,结果表明,该区储层孔隙类型主要以长石、硅质岩屑、石英和碳酸盐胶结物的粒间溶蚀孔隙和粒内溶蚀孔隙为主,纵向上在下沟组下段和赤金堡组顶发育有两个次生孔隙带。近物源快速堆积的沉积环境导致储层分选磨和圆差,矿物成分成熟度低,这是储层物性较差的根本原因。从成岩作用角度看,压实作用是导致储层物性变差的主要因素;粘土矿物和碳酸盐胶结物充填了大部分孔隙。胶结作用一方面充填于孔隙中使储层物性变差,另一方面又为后期溶蚀溶解奠定了物质基础。有机质热演化以及粘土矿物在成岩转化过程中释放的酸性水溶蚀及溶解作用产生大量次生孔隙,这是深部储层得以改善的主要原因。

The reservoirs of Ying＇er depression in Jiudong basin are characterized by low porosity and low permeability.The general poor physical properties of the reservoirs strictly restrict the exploration in this area.Based on analyses of thin sections,casting thin sections and fluorescence thin sections,X-ray diffraction analyses,SEM observations and mercury porosimetry measurements of the reservoir sandstones,this research shows that the main pore types are the inter-granular dissolved pore and intra-granular dissolved pore of feldspar,siliceous debris,quartz and carbonate cements.Two secondary pore zones are developed in the lower member of Xiagou formation and the top part of Chijinbao formation.Sandstones in the study area are characterized by poor sorting,poor roundness and low mineralogical maturity.These are the characteristics of fast accumulation and closure to provenance of the sediments.Mechanical compaction is the main factor in making the properties of reservoirs poor.Clay minerals and carbonate cements block pores.Cements fill in the pore space and destroy the reservoir property,meanwhile,they provide space for dissolution in the later stage,secondary pore is widely developed because of dissolution of minerals caused by acidic water that released by hydrocarbon generation process and diagenesis processes of clay minerals.It＇s the main factor that improves the reservoir property in the deep layers of the basin.