The Characteristics and Main Controlling Factors for the Formation of Micropores in Shale from the Niutitang Formation, Wenshuicun Section, Southwest China

Abstract

The characteristics of shale micro-pore development and its main influencing factors have important theoretical guiding significance for shale gas exploration and resource evaluation. In order to clarify the micro-pore development characteristics of lower Cambrian shale and the main controlling factors of micro-pore development, we used the lower Cambrian Niutitang formation shale, in the Wenshuicun section of the Guizhou Province in southwest China. The micro-pore development characteristics of the shale in the region were studied by argon ion profile field emission scanning electron microscopy and a low-temperature liquid nitrogen adsorption and desorption experimental system. The relationship between micro-pore and kerogen maceral composition, total organic carbon (TOC) content and different mineral content was analyzed in combination with mineral and geochemical characteristics. Inorganic pores (clay mineral pores, dissolution pores and pyrite intergranular pores) and micro-fractures (clay mineral shrinkage crack, tectonic fractures and overpressure fractures) were the main type of pore developed in the shale of the Niutitang formation in the Wenshuicun section, and no organic pores had developed. The pore size of shale is usually 2–50 nm, accounting for 58.33% of shale pores, e.g. mesopores. Clay mineral content has an obvious positive correlation with macropore volume and average pore diameter, and an obvious negative correlation with micropore volume. In addition, the content of feldspar in brittle minerals has a strong negative correlation with macropore volume and average pore diameter, and a strong positive correlation with micropore volume and BET-specific surface area. TOC content and the content of different kerogen macerals have no obvious correlation with the development of shale micropores in this region. It is concluded that inorganic mineral composition is the main controlling factor of micro-pore development within lower Cambrian shale, and organic matter abundance and maceral content have little influence on the micro-pore development. This study provides a case study for the characteristics of micropores in lower Cambrian shale in China.

Different Fracture Liquids under the Action of Enclosure of Dense Sandstone Reservoir Micro-Damage Characteristics Study

“…Double-season ammonium salt clay stabilizers replaced the original clay stabilizer to prepare new fissure [11,12]. We mainly evaluate the basic performance of the fracture fluid for different fracturing liquids, and less micro-pores before and after the damage [13][14][15]. At the same time, with the increase of the feed pressure, the throat and large pores of the rock heart are compressed to deform, and some ultra-fine small pores are even closed [16].…”

The depositional settings of organic-rich shale in the faulted lacustrine basin: A case study of the Y1 Member of the Yingcheng Formation in the Songliao Basin

“…Some differences emerge in these studies, particularly in the main controlling factors of the accumulation of organic matter. Some researchers indicate that high productivity is the primary factor for the formation of organic-rich shale [13][14][15][16], while others believe that the key to the high organic matter content of lacustrine shale lies in organic matter preservation [17,18]. To further explore the impact of the sedimentary environment (high productivity) and external factors potentially affecting preservation conditions, the shale of the Y1 Member is studied in this paper.…”