川西坳陷须三段致密砂岩优质储层特征及控制因素

The characteristics and main controlling factors of high quality tight sandstone reservoir in the 3th member of Xujiahe Formation inWest Sichuan Depression

【研究目的】致密砂岩优质储层发育特征及控制因素已成为川西坳陷开展源储一体的常规与非常规油气协同勘探的重难点问题;探讨致密砂岩储层特征与致密气成藏的关系。【研究方法】运用地球化学、地球物理和沉积学等分析方法,对晚三叠世须三段致密储层发育特征进行研究。【研究结果】分析测试数据揭示须家河组须三段储层的孔隙度分布在1.11%~5.70%,渗透率分布在(0.0017~0.45)×10^(-3)μm^(2),属于致密储层范畴。基于砂岩粒度大小,川西坳陷须三段致密储层识别出3类优质储层,即以石英砂岩和岩屑石英砂岩为主的粗砂,以岩屑砂岩、岩屑石英砂岩和长石岩屑砂岩为主的中砂和细砂。研究区粗砂较少发育,厚度较大的中砂和细砂在中亚段和上亚段的三角洲前缘相中部、高位体系域中晚期与低位体系域早期较发育,属于低孔低渗—特低孔特低渗致密储层,储集空间以次生孔隙、微孔隙和微裂缝为主。【结论】致密砂岩优质储层发育主要受岩性、沉积、层序和成岩作用协同控制。岩性控制优质储层的发育类型,沉积和层序控制优质储层的发育位置,成岩作用控制优质储层的形成;致密砂岩储层特征与致密气成藏的关系。

This paper is the result of oil and gas exploration engineering.[Objective]The development characteristics and controlling factors of high quality tight sandstone reservoirs have become important and difficult issues in the cooperative exploration of conventional and unconventional oil and gas in the integration of source and reservoir in western Sichuan Depression,the relationship between tight sandstone reservoir characteristics and tight gas accumulation is discussed.[Methods]Geochemical,geophysical and sedimentological analysis methods were used to study the development characteristics of tight reservoir in the 3th member of Xujiahe Formation.[Results]Analysis of test data revealed the porosity of the reservoir in the third member of the Xujiahe Formation is distributed between 1.11%-5.70%and the permeability is distributed between(0.0017-0.45)×10^(-3)μm^(2),which belongs to the category of tight reservoir.Based on the grain size of sandstone,three types of high quality reservoirs are identified in tight reservoir of the third Member of Xujiahe Formation in western Sichuan Depression,namely quartz sandstone and lithic quartz sandstone mainly coarse sandstone,the medium and fine sandstone are mainly lithic sandstone,lithic quartz sandstone and feldspar lithic sandstone.Coarse sandstone is less developed in the study area,and medium and fine sandstone with large thickness are relatively developed in the middle of delta front facies of the central and upper sub-member,and in the late stage and early stage of the high and low system tracts.It is a tight reservoir with low porosity and low permeability,ultra-low porosity and ultra-low permeability,and the reservoir space is dominated by secondary pores,micro-pores and micro-fractures.[Conclusions]The development of high quality tight sandstone reservoir is mainly controlled by lithology,sedimentation,stratigraphic sequence and diagenesis.Lithology controls the development type of high-quality reservoir,sedimentation and stratigraphic sequence control the development location of high-quality reservoir,and diagenesis control the formation of high-quality reservoir,tight gas accumulation is restricted by tight sandstone reservoir distribution.