黔西北威宁地区龙参1井下石炭统旧司组—祥摆组海相页岩气储层物性及含气性特征

Physical properties and gas-bearing properties of marine shale gas reservoirs in the Lower Carboniferous Jiusi Formation-Xiangbai Formation in Well Longcan 1,Weining area,Northwest Guizhou

黔西北下石炭统旧司组—祥摆组是重要的海相页岩层系,为进一步加强贵州省页岩气的基础地质勘察,形成贵州特色页岩气地质理论,以威宁龙街向斜龙参1井下石炭统旧司组—祥摆组页岩为研究对象,通过岩石学、地球化学、储层物性及含气性相关测试评价了其勘探开发潜力。结果表明:①祥摆组页岩厚度介于74.76~255.6 m之间,有机碳含量中等(平均为2.01%)、热演化程度较高(R_(o,max)值平均为2.54%);显微组分以壳质组(平均为43.31%)为主,腐泥组(平均为38.08%)次之;有机质类型为Ⅱ1型和Ⅱ2型。②黏土矿物含量较多(质量分数平均为45.4%),石英次之(质量分数平均为38.08%),脆性指数整体较高。③孔隙度中等(平均为4.77%),核磁渗透率范围跨度较大,介于(0.0797~4.63)×10^(-6)μm^(2)之间,平均为1.32×10^(-6)μm^(2),属低渗储层;主要发育微裂缝、粒内孔、粒间孔和有机质孔;孔隙比表面积(平均为14.387 m^(2)/g)和总孔体积(平均为0.01676 cm^(3)/g)较大,以介孔为主,平均孔径介于3.79~8.45 nm之间,平均为5.89 nm。④旧司组—祥摆组含气量中等,最高达1.48 m^(3)/t,TOC是泥页岩含气性的主要影响因素,TOC与兰氏体积、总孔体积呈良好的正相关关系,石英与TOC、R_(O)呈正相关关系。旧司组—祥摆组页岩气储层符合产业开发条件,与国内外页岩储层特征综合对比认为,旧司组—祥摆组深色页岩有机质丰度中等,热演化程度较高,脆性指数高,多介孔,有较好的探勘开发潜力。

The Jiusi-Xiangbai formations of Lower Carboniferous in northwest Guizhou are important marine shale series.In order to further strengthen the basic geological survey of shale gas in Guizhou,the geological theory of shale gas with Guizhou characteristics is formed.In this paper,the exploration and development potential of shale in Jiusi-Xiangbai formations of Well Longcan 1 in Longjie Syncline of Weining is evaluated by petrology,geochemistry,reservoir physical properties and gas bearing test.The results show that:(1)The shale thickness of Xiangbai Formation is 74.76-255.6 m,the organic carbon content is medium(average,2.01%),and the thermal evolution degree is high(R_(O,max)average,2.54%);the microscopic components were mainly in the shell group(average 43.31%),followed by the sapropel group(average,38.08%).Types of organic matter are II1 and II2.(2)The clay mineral content is relatively high(with an average mass fraction of 45.4%),followed by quartz(with an average mass fraction of 38.08%),and the brittleness index is overall high.(3)The porosity is medium(average,4.77%),and the range of NMR permeability is large,ranging at(0.0797-4.63)×10^(-6)μm^(2),with an average of 1.32×10^(-6)μm^(2),belonging to low permeability reservoirs;microcracks,intragranular pores,intergranular pores and organic pores are mainly developed;pore specific surface area(average 14.387 m~2/g)and total pore volume(average 0.01676 cm~3/g)are large,mainly mesoporous,average pore size is 3.79-8.45 nm,average 5.89 nm.(4)The gas content of the Jiusi-Xiangbai formations are moderate,up to 1.48 m~3/t.It is found that TOC is the main factor affecting the gas content of mud shale.It is positively correlated with TOC and RO.In line with the conditions for industrial development,and a comprehensive comparison with the characteristics of shale reservoirs at home and abroad,it is believed that the dark shale of the Jiusi-Xiangbai formations have medium abundance of organic matter,high thermal evolution degree,high brittleness index,multiple mesoporous,and good exploration and development potential.