鄂尔多斯盆地乌拉力克组页岩储层孔径表征及其主控因素

Pore size characterization and their mainly controlling factors in Wulalike Formation shale,Ordas Basin

以忠平1井乌拉力克组页岩为研究对象,应用二氧化碳和氮气吸附、高压压汞、氦气孔隙度、水平衡实验等方法,结合分形维理论表征和探讨页岩孔隙、孔径分布及其控制因素。研究结果表明:乌拉力克组页岩中微孔体积平均为0.00372 cm^(3)/g,占总孔体积的20%;介孔体积平均为0.01186 cm^(3)/g,占比为62%;宏孔体积平均为0.00333 cm^(3)/g,占总孔隙的18%;页岩比表面积为14.47~21.81 cm^(2)/g,微孔平均贡献67.92%比表面积,介孔31.93%,宏孔0.15%,直径<10 nm的孔隙贡献92.23%的比表面积;页岩微孔分形维数D_(m)为2.29~2.66,介孔分形维数D_(1)为1.31~1.51,介孔分形维数D_(2)为2.74~2.79。页岩孔体积和比表面积与黏土矿物和长石质量分数呈正相关,与石英质量分数呈负相关;水分降低孔体积和比表面积大约10%以上,水分和可溶沥青并存会降低储层孔隙和比表面积20%以上。因此,乌拉力克组页岩以介孔为主且孔隙非均质强,孔隙主要受矿物组分石英、长石、黏土矿物、水分与可溶沥青控制与影响。

Carbon dioxide and nitrogen adsorption,high pressure mercery injection,helium porosity,moisture balance,fraction dimension models etc.were used to determine the shale pore size distribution,pore volume,specific surface area.The results show that micropore volume average was 0.00372 cm^(3)/g,accounting for 20 percent of all pores in the shale,mesopore volume 0.01186 cm^(3)/g,accounting for 62 percent,macropore volume 0.00333 cm^(3)/g,accounting for 18 percent;specific surface area varied from 14.47 cm^(2)/g to 21.81 cm^(2)/g,micropore contributing to 67.92 percent of specific surface area,mesopore 31.93 percent,macropore 0.15 percent,and pore less than 10 nm in diameter accounted for 92.23%percent of all surface area of the shale;fraction dimension of micropore ranged from 2.29 to 2.66 with the mean value of 2.48;fraction dimension D_(1) of nitrogen adsorption varied from 1.31 to 1.51,D_(2) changed from 2.74 to 2.79.Shale pore and surface areas have the positive relationship with clay and feldspar contents,negative correction with quartz,moisture can reduce pore volume and surface area of the shale beyond or so 10%percent,and moisture and bitumen existing together could drastically decrease the pore volume and surface area of the shale,up to more than 20%percent.Therefore,the Wulalike Formation shales were dominantly mesopore in volume,and pore volume and surface area were controlled by clay,feldspar,quartz,bitumen,moisture.