中美海相页岩气地质特征对比研究

通过中国海相页岩气详细研究和美国典型页岩气区带解剖，对比研究了中美页岩气地质特征的异同，这些研究对指导我国四川盆地海相页岩气的研究具有重要理论和实践意义。 ①美国Barnett页岩、Marcellus页岩和Haynesville页岩气区带的盆地类型为前陆盆地，中国四川早古生代盆地为克拉通。沉积环境均为深水陆棚，岩石类型以硅质和硅质钙质页岩为主，脆性矿物含量高。②Barnett页岩TOC值为3%~13%，平均为4.5%，Marcellus页岩TOC值为3%~12%，平均为4.0%，Haynesville页岩TOC值为0.5%~4%。四川盆地五峰组-龙马溪组和筇竹寺组页岩TOC值分别为1.5%~3%和2.5%~4.5%。③美国三大页岩成熟度适中，四川盆地海相页岩处于过成熟阶段。Barnett页岩、Marcellus页岩和Haynesville页岩R_O值分别为0.5%~2.1%、1.2%～3.5%和1.2%~3%。四川盆地筇竹寺组页岩R_O值一般为2.5%~4.5%，平均为3.5%，龙马溪组页岩R_O值为1.5%~3%。 ④Barnett页岩核心区厚度为30~180m，总孔隙度为4%~5%，基质渗透率小于1×10^-3μm²，Marcellus页岩厚度为 15～60m，孔隙度平均为10%，渗透率小于1×10^-3μm²， Haynesville页岩厚度为70~100m，孔隙度为8%~9%，渗透率小于5×10^-3μm²，四川盆地五峰组-龙马溪组页岩厚度为25~120m，孔隙度为3%~10%，渗透率为(0.01~)×10^-3μm²，筇竹寺组页岩厚度为40~100m，孔隙度为0.1%~3%，渗透率为(0.01~42)×10^-3μm²。⑤Barnett页岩、Marcellus页岩和Haynesville页岩含气量分别为4.2~9.9m³/t、1.70～2.83m³/t和2.5~9m³/t。四川盆地五峰组-龙马溪组和筇竹寺组页岩含气量分别为1.7~4.5m³/t和0.55~1.2m³/t。中国海相页岩吸附气含量大于美国。⑥美国海相页岩埋深为1 220~3 990m,中国海相页岩埋深可高达5 000m，一般为1 500~4 000m;Barnett页岩和筇竹寺组页岩为正常地层压力，压力系数分别为0.99~1.01和1，Marcellus页岩，Haynesville页岩和五峰组-龙马溪组为异常高压，地层压力系数分别为0.9~1.4、1.61~2.07和1~2.3。⑦除四川盆地筇竹寺组页岩外，其他4套页岩均具有良好封盖层，有利于天然气保存。⑧美国地表条件更有利，多以平原为主，而四川多为丘陵。 ⑨四川盆地五峰组-龙马溪组页岩气地质资源量为17.5×10¹²m³，技术可采资源量为1.77×10¹²m³，筇竹寺组页岩气地质资源量为8.86×10¹²m³，技术可采资源量为0.886×10¹²m³。

A Comparative Study of the Geological Feature of Marine Shale Gas between China and the United States

Through detailed studies of marine shale gas in China and investigation of typical shale gas zones in the United States,similarities and differences of geological features of the shale gas in USA and China were summarized.The comparative study is of important theoretical and practical significance for marine shale gas in Sichuan Basin.(1)Barnett,Marcellus and Haynesville shale basins are foreland basin,while Sichuan basin in Paleozoic is intra-craton basin.Their depositional environments are deep water shelf,mainly siliceous and calcareous shale,with high brittleness mineral content.(2)TOC of Barnett shale is 3%-13%，averaged at 4.5%;Marcellus is 3%-12%,averaged at 4.0%;and Haynesville shale is 0.5%-4%.TOC of Wufeng-Longmaxi and Qiongzhusi is 1.5%-3% and 2.5%-4.5%,respectively.(3)Maturity of three major shale formations is moderate,while that of Sichuan Basin is at over-mature stage.TheR_O values of the Barnett,Marcellus and Haynesville formations are 0.5%-2.1%，1.2%-3.5%，and 1.2%-3%,respectively.However,theR_Ovalues of the Longmaxi and Qiongzhusi formations are 2.5%-4.5% and 1.5%-3%,respectively.(4)Barnett shale has thickness of 30-180m,porosity of 4%-5%,and permeability less than 1×10^-3μm²;Marcellus shale has thickness of 15-60m,porosity averagely of 10%,and permeability less than 1×10^-3μm²;Haynesville shale has thickness of 70-100m,porosity of 8%-9%,and permeability less than 5×10^-3μm².Longmaxi shale has thickness of 25-120m,porosity of 3%-10%,and permeability of(0.01-1)×10^-3μm²;Qiongzhuxi shale has thickness of 40-100m,porosity of 0.1%-3%,and permeability of(0.01-42)×10^-3μm².(5)Gas contents of Barnett,Marcellus and Haynesville shale are 4.2-9.9,1.70-2.83 and 2.5-9m³/t,respectively,and that of Longmaxi and Qiongzhusi shale are 1.7-4.5 and 0.55-1.2 m³/t,respectively.(6)Except Qiongzhuxi shale,the other four shale formations have good sedimentary cover,which is conducive to gas preservation.(7)American shales have more favorable surface conditions,mostly plains,while mostly hills in Sichuan Basin.(8)Except Haynesville shale,fractures are well developed in other shale formations.(9)Shale gases from both the USA and China have rich resource potential.The Geological and technically recoverable resources of Longmaxi Formation are 17.5×10¹²m³ and 1.77×10¹²m³,respectively while that of Qiongzhusi Formation are 8.86×10¹²m³ and 0.886×10¹²m³,respectively.