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利用SEM-PCAS孔隙定量表征技术与低压N_2等温吸附实验研究X井深度为6 875~8 042m超深层泥页岩的纳米孔隙特征,并选取四川盆地及周缘地区从地表到5km左右的样品组作为对比,探索深埋藏作用对泥页岩孔隙系统的影响。研究发现,X井志留系龙马溪组、奥陶系五峰组及下寒武统筇竹寺组超深层泥页岩32个样品的孔隙特征相似,孔隙类型以有机质孔、粒间孔为主,孔隙形态以狭长-裂缝型为主。N_2等温吸附线类型为IV-H3型,QSDFT孔径分布显示其纳米孔隙主要分布于4~16nm段,BET比表面积为8.63~16.13m2/g。与对照组样品相比,X井超深层泥页岩的孔径分布更加分散,微孔体积和微孔比表面积更小,介孔/微孔的体积比值及介孔/微孔的比表面积比值比非超深层泥页岩均具有数量级的优势。X井超深层泥页岩的孔隙特征主要受埋藏深度控制,深埋藏作用会使泥页岩孔径缩小并改变孔隙的形态。
Nanopore characteristics of deep ultra-deep shale with a depth of 6 875-8 042 m were studied by means of SEM-PCAS pore quantitative characterization and low-pressure N 2 isothermal adsorption experiments. Specimens from the surface to around 5 km in the Sichuan Basin and its surrounding areas were selected as In contrast, we explore the effect of deep burial on the pore system of shale. It is found that the pore characteristics of 32 samples of Longzixi, Ordovician Wufeng Formation and Lower Cambrian Qiongzhusi ultra-deep shale are similar, and the pore types are dominated by organic matter pores and intergranular pores , Pore morphology to narrow - crack-based. The type of isothermal adsorption line for N_2 is type IV-H3. The pore size distribution of QSDFT shows that the pore size of N_2 is mainly distributed in the range of 4 ~ 16nm, and the BET specific surface area is 8.63 ~ 16.13m2 / g. In comparison with the control samples, the pore size distribution of ultra-deep shale in X-well is more dispersed with smaller pore volume and micropore specific surface area. The mesopore / micropore volume ratio and mesopore / micropore specific surface area ratio Non-ultra-deep shale has an order of magnitude advantage. The pore characteristics of ultra-deep shale in the X-well are mainly controlled by the burial depth. The deep-burial will reduce the pore size of the shale and change the shape of the pores.