松辽盆地南部海坨子地区超低渗透储层特征与形成因素

通过详细的岩心观察和描述,同时结合铸体薄片、扫描电镜、X-射线衍射、压汞、核磁共振以及物性等资料的研究,认为海坨子地区扶余油层为末端扇中部亚相沉积,储层岩石类型主要为岩屑长石砂岩和长石岩屑砂岩,孔喉结构为小孔隙、细喉或微细喉型,束缚水饱和度高,渗流能力差,属于超低渗透储层。沉积作用和成岩作用是扶余油层超低渗透储层形成的关键。末端扇沉积控制了扶余油层原始沉积物的粒度、碎屑成分以及填隙物成分和含量,使得储层初始孔渗性较差,同时强烈的机械压实作用导致扶余油层原生粒间孔隙体积直线下降,而胶结作用,尤其碳酸盐连晶状基底胶结几乎完全封堵了孔喉,喉道内伊利石等粘土矿物的搭桥生长,也使孔喉变得越来越曲折、狭窄,储层渗流能力因此遭受严重破坏。此外,末端扇储层中大量非渗透性隔夹层导致的强非均质性也是超低渗透储层形成的一个因素。溶蚀作用对扶余油层渗透性的改善有限,但成岩微裂缝和构造裂缝的发育对海坨子地区超低渗透油藏的开发起着至关重要的作用。

Characteristics and form factors of ultralow permeable reservoir in Haituozi area in the southern Songliao Basin

According to careful observation of core and analysis of cast thin section,SEM,X-ray,mercury penetration,nuclear magnetic resonance and physical property,the Fuyu reservoir is part of middle-terminal fan sand which is chiefly composed of lithic arkose and arkose.The sandstone reservoir is ultralow permeable reservoir with high bound water saturation,small pore and micro to fine porous throats.Sedimentation and diagenesis are key factors of Fuyu ultralow permeable reservoir.The Fuyu reservoir is mainly controlled by deposition and diagenesis.Terminal deposit which affects grain size,clastic constituents and interstitial material result in low original poroperm characteristics.Strong compaction destroyed great quantity of inter granular pores.Cementation,especially basal carbonate cementation completely plugged pores and throats and clay minerals generate as bridge in throats what seriously decreased reservoir permeability.Impermeable barrier,for example argillized and calcarinate zones are favor of generation of ultralow reservoir.The dissolution could not improve reservoir quality obviously.Diagenetic fracture and structural cracks play a good role in ultralow hydrocarbon reservoir of Haituozi.