CHARACTERIZATION OF THE PORE STRUCTURE AND ITS INFLUENCING FACTOR OF LOWER PALEOZOIC SHALE IN DABASHAN AREA, CHINA

摘要

The Lower Paleozoic shale in the Dabashan area has good potential for shale gas exploration. The pore structure of the shale is an important factor affecting the occurrence of Lower Paleozoic shale gas in the area. Aiming at the understanding of the pore structure of the Lower Paleozoic shale in the Dabashan area, this study uses low-temperature nitrogen adsorption experiment to characterize the micropore structure of the Lower Paleozoic shale in the Dabashan area. By calculating the specific surface area (m2/g), pore volume (cm3/g), average pore size (nm), and total micropore volume (cm3/g), the pore structure characteristics of these shale samples are determined. Based on the results of XRD and TOC, the main controlling factors of shale pore development were discussed. The experimental results show that the specific surface area of the Lower Paleozoic shale in the Dabashan area is 5.66-22.2 m2/g, the pore volume is 0.02579-0.04674 cm3/g, the average pore size is 7.7768-14.65647 nm, and the total micropore pore volume is 0.00187- 0.00878 cm3/g. The TOC of shale ranges from 1.42% to 3.45% and the mineral content is mainly quartz and illite. The development of nanopores in shale reservoirs is dominated by the mesopores (20-50 nm), showing good shale gas storage conditions. TOC and illite content are the main factors controlling the pore structure and specific surface area of shale reservoirs. This study provides a theoretical basis for the evaluation of shale gas resource potential in this area.