四川盆地及周缘地区五峰—龙马溪组页岩气概况及前景评价

探讨四川盆地及周缘地区上奥陶统-下志留统五峰-龙马溪组黑色页岩的基础地质特征,并对该层页岩气前景进行评价。通过野外露头、钻井和地震剖面资料研究表明,四川盆地及周缘地区五峰-龙马溪组泥页岩分布于环乐山-龙女寺和黔中加里东古隆起地区,向川南、川北和川东方向逐渐变厚,厚度达200～500m;其中黑色页岩厚度的分布趋势与之相似,一般为20～80m。有机碳质量分数>1%,属腐泥型Ⅰ型干酪根,一般Ro>2%。黑色页岩段为海侵至最大海平面时的沉积产物,现今埋藏较浅,盆地内川南地区埋深1.5～3km,鄂西渝东地区埋深1.5～3km。川东及鄂西渝东过渡带埋深2～3.5km的黑色页岩段将是页岩气勘探的主要目标区,大巴山前缘是未来勘探的潜在有利区。

General situation and prospect evaluation of the shale gas in Wufeng-Longmaxi Formation of Sichuan Basin and surrounding areas

In Sichuan Basin and surrounding areas,the mud shale in Wufeng-Longmaxi Formation of Upper Ordovician to Lower Silurian is distributed in Leshan-Longnüsi and the Jialidong paleo-uplift area in the middle of Guizhou,and the thickens increasingly to the north,the south and the east.The thickness of the mud shale is 200~500 m,and the thickness of the black shale has the same distribution trends and the thickness is generally 20~80 m.The fraction of organic carbon(TOC) of the shale is more than 1% in most areas of Sichuan Basin,belonging to sapropelicⅠkerogen,generally Ro>2%.The black shale section consists of the sediments of transgression to maximum sea level,and the nowaday buried depth is relatively shallow.The buried depth in the south of Sichuan Basin is 1.5~3 km,that in west of Hubei and the east of Chongqing area is 1.5~3 km.The main target zone of the shale gas is the transitional zone from the east of Sichuan Basin to the west of Hubei and the east of Chongqing area.The buried depth of the shale in this zone is 2~3.5 km,and the front of the Daba mountain is the potential exploration advantageous area in future.