川西新场地区上三叠统须家河组二、四段物源及储层特征差异对比研究

Comparative Study on the Provenance and Reservoir Characteristics of the Second and Fourth Members of the Upper Triassic Xujiahe Formation in the Xinchang Area,Western Sichuan,China

随着勘探由常规油气向非常规油气的深入,致密砂岩气逐渐成为勘探热点。川西坳陷新场地区须二段、四段致密砂岩储层是须家河组主要的产气层。受沉积环境、埋深、成岩环境的影响,不同物源下储层砂岩矿物组成、成岩演化以及储集物性等方面存在显著差异。首先,结合前人研究成果,通过砂岩类型和岩屑类型特征分析研究区须二段、须四段的物源方向。其次,通过储层岩石学特征、物性特征、储集空间特征及储集层成岩作用类型探究物源对储层特征的影响。最后,分别讨论不同物源下研究区须二段、须四段储层特征的差异性,揭示物源对储层的控制作用。取得认识如下:(1)须二段主物源区是米仓山—大巴山,须四段主物源区是龙门山;(2)须二段,米仓山—大巴山物源较龙门山物源控制的储层压实作用及硅质胶结作用略强,绿泥石薄膜发育,碳酸盐胶结作用弱。须四段,龙门山物源较米仓山—大巴山物源控制的储层碳酸盐岩屑极大地提高了储层的抗压实能力,长石溶蚀作用显著,方解石胶结作用略弱;(3)龙门山物源体系下,须二段绿泥石胶结和长石溶蚀作用主要改变储层物性,碳酸盐胶结和硅质胶结作用是储层致密化的关键因素;须四段溶蚀作用和相对较弱的压实作用是储层孔隙发育的主要因素,碳酸盐胶结作用是储层致密化的关键因素。米仓山—大巴山物源体系下,须二段绿泥石胶结和长石溶蚀作用是改善储层物性的主要因素,硅质胶结作用是储层致密化的关键因素;须四段碳酸盐岩屑的抗压实能力使原生孔隙保存较好,溶蚀作用使次生孔隙发育,二者是孔隙发育的主控因素,碳酸盐胶结作用是储层致密化的关键因素。同一层位不同物源控制的储层成岩作用特征有所差异,且同一物源控制不同层位的储层成岩作用特征存在明显差异。

With the deepening of exploration from conventional to unconventional oil and gas,tight sandstone gas has gradually become a hot spot of exploration.The tight sandstone reservoirs of the Second and Fourth members of the Xujiahe Formation in the Xinchang area of the Western Sichuan Depression are the main gas producing layers of the Xujiahe Formation.Influenced by sedimentary environment,burial depth,and diagenetic environment,there are significant differences in mineral composition,diagenetic evolution,and reservoir physical properties for the sand⁃stones of different provenance in this area.First,through the characteristics of sandstone and debris type,combined with previous research results,the provenance directions of the Second and Fourth members of the Xujiahe Formation in the study area are analyzed.Second,the influence of provenance on reservoir characteristics is explored through reservoir petrological characteristics,physical properties,reservoir space characteristics,and reservoir diagenesis types.Finally,the differences in reservoir characteristics of the Second and Fourth members of the Xujiahe Formation in the study area under different provenances are discussed,revealing the control effect of provenance on reservoir.Get the following understanding:(1)The main provenance area of the Second member of the Xujiahe Formation is Micangshan-Dabashan,and the main provenance area of the Fourth member of the Xujiahe Formation is Longmenshan;(2)In the Second member of the Xujiahe Formation,the reservoir compaction and siliceous cemen⁃tation controlled by Micangshan-Dabashan provenance were stronger than those controlled by Longmenshan prove⁃nance,a chlorite film developed,and carbonate cementation was weak.In the Fourth member of the Xujiahe Forma⁃tion,the carbonate debris of the reservoir controlled by the Longmenshan provenance greatly improved the compac⁃tion resistance of the reservoir compared with the Micangshan-Dabashan provenance.The feldspar dissolution was sig⁃nificant,and the calcite cementation was slightly weak;(3)Under the provenance of Longmenshan,the chlorite ce⁃mentation and feldspar dissolution of the Second member of the Xujiahe Formation mainly changed the reservoir phys⁃ical properties.Carbonate and siliceous cementation were the key factors for reservoir densification.The dissolution and relatively weak compaction of the Fourth member of the Xujiahe Formation were the main factors of reservoir pore development,and carbonate cementation was the key factor of reservoir densification.Under the provenance of Micangshan-Dabashan,chlorite cementation and feldspar dissolution were the main factors improving reservoir physi⁃cal properties,and siliceous cementation was the key factor to reservoir densification.The dissolution of the Fourth member of the Xujiahe Formation and the anti-compaction ability of carbonate debris were the main factors improving the physical properties of the reservoir,and carbonate cementation was the key factor of reservoir density.The diage⁃netic characteristics of reservoirs controlled by different provenances in the same layer are distinct and the diagenetic characteristics of different layers of reservoirs under the control of the same provenance display obvious differences.