石油与天然气地质 ›› 2011, Vol. 32 ›› Issue (4): 542-550,559.doi: 10.11743/ogg20110407

• 石油与天然气地质 • 上一篇    下一篇

川西雷口坡组碳酸盐岩储层特征及成岩作用

  

  • 出版日期:2011-08-28 发布日期:2011-09-26

A study on characteristics and diagenesis of carbonate reservoirs in the Middle Triassic Leikoupo Formation in western Sichuan Depression

  • Online:2011-08-28 Published:2011-09-26

摘要:

摘要:川西雷口坡组储层较发育,(藻)砂屑白云岩、中-细晶白云岩为主要储集岩,粒间溶孔、粒内溶孔为主要孔隙类型,孔隙结构以中-小孔细喉为主,总体显示出低孔低渗的特征。雷口坡组(藻)砂屑白云岩在川西坳陷的西缘分布稳定,厚度较大,总体上以海底、埋藏成岩环境为主,北段受到大气水成岩环境的影响,向南逐渐减弱。受成岩环境的控制,雷口坡组(藻)砂屑白云岩主要的成岩作用类型有压实、压溶作用、胶结充填作用、溶蚀作用、白云岩化作用等,其中,建设性的成岩作用主要有溶蚀作用、白云岩化作用、晚期破裂作用。溶蚀作用中的准同生期暴露溶蚀、表生溶蚀,主要分布于川西坳陷北部中坝构造带附近;而埋藏溶蚀作用对于川西坳陷中、南段储层的发育也具有非常重要的意义。鲕粒、砂屑白云岩主要与早期回流渗透、埋藏白云岩化有关。综合沉积、成岩特征,雷口坡组在川西坳陷北段南部砂屑滩体发育,且经历了准同生期大气水溶蚀、表生期溶蚀和埋藏溶蚀作用,是最有利的勘探区;而在中段的金河剖面的鲕粒、砂屑白云岩粒间(溶)孔中,发现有大量的沥青,表明发生过油气的运移或聚集,也是值得重视的有利勘探区域。

关键词: 关键词:储层特征, 成岩环境, 成岩类型, 雷口坡组, 川西坳陷

Abstract:

Abstract: Reservoirs are relatively welldeveloped in the Leikoupo Formation of western Sichuan Depression. They are mainly algal dolorenite and mediumfine crystalline dolostone reservoirs with intergranular and intragranular dissolution pores. The pore structures are dominated by mediumfine pore throat. As a whole, these reservoirs are low in both porosity and permeability. Thick algal dolorenite reservoirs in the Formation distribute widely in western margin of the Basin. As a whole, the reservoirs were formed in seabed burial diagenetic environment. However, the west segment of the Depression shows evidence of meteoric diagenesis which weakens southward. Controlled by different diagenetic enviroments, the reservoirs experienced such diagenetic processes as compaction, pressuresolution, cementation, dissolution, dolomitization, and etc. Among them, the dissolution, dolomitization, and later fracturing are constructive diagenesis. The penecontemporaneous exposure dissolution and hypergene dissolution mainly occurred in northern Zhongba structural belt, while the burial dissolution contributed a lot to the formation of reservoirs in the midsouth segment of the Depression. The oolitic and dolorenite are thought to be mainly related to early back flow seepage and burial dolomitization. A comprehensive study of sedimentation and diagnesis of the Depression indicates that the Leikoupo Formation in the south of the northern segment of the Depression has welldeveloped arenitic shoals and experienced penecontemporaneous meteoric dissolution, hypergene dissolution and burial dissolution, and thus may be the most potential exploration targets. But attention shall also be paid to the middle segment for the fact that bitumen is observed in the intergranular pores of ooliteic and dolorenite there. 

Key words: Key words: reservoir property, digenetic environment, diagenetic type, Leikoupo Formation, Western Sichuan Depression