Influence factors and an evaluation method about breakthrough pressure of carbonate rocks: An experimental study on the Ordovician of carbonate rock from the Kalpin area, Tarim Basin, China

Abstract There are many oil and gas fields around the world that are sealed by tight carbonate caprocks. Compared with gypsum rocks and shales, tight carbonate caprocks are characterized by brittleness and ease of structural fracturing and dissolving in acidic groundwater. The breakthrough pressure (BP) is a significant indicator that indicates the sealing capacity of the caprocks. Therefore, we conducted a series of experiments, including effective porosity, permeability, casting thin-sections, BP, mineral composition, microstructural characteristics and clay minerals contents on carbonate samples from Ordovician system in the Kalpin area, Tarim Basin, China to research factors that affect the BP of carbonate caprocks. According to the experimental data analysis, the BP deceases with macropore proportions and increases with proportions of micropore and mesopore volume. Due to the large macropore proportion and low clay content (