松辽盆地梨树断陷东南斜坡带营城——沙河子组储层特征及主控因素

Reservoir characteristics and main controlling factors of Yingcheng-Shahezi formations in southeast ramp region of Lishu Fault Depression,Songliao Basin

松辽盆地梨树断陷下白垩统营城—沙河子组砂岩储层非均质性强,钻探成功率较低。通过岩心观察、薄片鉴定及定量统计、孔渗分析、压汞等研究,认为梨树断陷东南斜坡带营城—沙河子组储层以含砾细砂岩为主,其次为细砂岩、中砂岩,具有粗碎屑、石英含量较低,分选、磨圆较差等组构特征;岩石类型为长石岩屑砂岩、岩屑砂岩、岩屑长石砂岩及少量长石砂岩,长石和岩屑含量高,填隙物以泥质、方解石为主;储层物性较差,非均质性强,整体为特低孔、特低渗储层。储层孔隙类型有原生粒间孔、次生溶孔、裂隙等,以原生孔为主,个别地区以裂隙为主。储层的孔隙发育受沉积环境和成岩作用的控制,晚期构造裂隙作用不可忽视。储层成岩作用类型多样,胶结充填和机械压实作用使原生孔隙大量减少,溶蚀和构造破裂则有效改善了储层的物性;特别是晚期构造裂隙作用,产生了不同类型的裂隙,增加了孔隙空间及渗透性,这可能是东南斜坡带秦家屯、金山等地区形成高产油气田的重要原因之一。

The sandstone reservoirs of the Lower Cretaceous Yingcheng-Shahezi formations in the Lishu FaultDepression of the Songliao Basin have a strong heterogeneity and a low exploration success rate. Through coreobservation, thin section identification and quantitative statistics, porosity and permeability analysis, mercuryintrusion, etc., it was concluded that the Yingcheng -Shahezi formations in the southeast ramp of Lishu FaultDepression are dominated by pebbly sandstones, followed by fine-grained and medium-grained sandstones, withlow contents of coarse debris and quartz, and low compositional and structural maturities. The main components arefeldspathic lithic sandstones, lithic sandstones, and lithic feldspar sandstones, with a small amount of feldsparsandstones. Feldspars and rock debris are in high content, and the interstitial material is mainly argillaceous andcalcite. The Yingcheng-Shahezi formations have an ultra-low porosity and an ultra-low permeability with a strongheterogeneity. They consist of primary intergranular pores, secondary dissolved pores and fissures, mainly primarypores, and fractures in some areas. The pore development of reservoirs is controlled by sedimentary environmentand diagenesis, and the role of late tectonic fractures cannot be ignored. The primary pores were greatly reduced bycementation and mechanical compaction, while dissolution and structural rupture effectively improved the physicalproperties of the reservoir. In particular, the late tectonic fissures produced different types of fractures andincreased porosity and permeability, which may be one of the important reasons for the formation of high-yield oiland gas fields in the Qinjiatun and Jinshan areas of the southeast ramp.