Experimental analysis of aquathermal pressuring under high temperature conditions and its geological implications

Overpressure generation mechanism is very important for the research of hydrocarbon accumulation. We collected samples from typical wells in high temperature basins, made use of a double-axial pressurization testing system for pore fluid aquathermal pressuring, and measured the amplitude of aquathermal pressuring for different geological conditions. Results indicated that the relationship between temperature and pressure was not linear but exponential on the condition of high aquathermal pressuring in shale sealed systems, while the amplitude of aquathermal pressuring in isolated systems was higher than that in shale sealed systems. The fine variation of properties of sealed shales would lead to a large amplitude of aquathermal pressuring in shale sealed systems, and the greater porosity of sand samples would lead to larger amplitude of aquathermal pressuring. Experimental results induced two geological implications. In high temperature basins, aquathermal pressuring in shale sealed systems increases significantly with burial depth. It cannot be neglected and could be one of the main overpressure generation mechanisms. The quality of sealed shale decides the amplitude of aquathermal pressuring, and sand porosity could affect the amplitude of aquathermal pressuring, so in geological conditions, high porosity sand embedded in low porosity shale layers is more likely to lead to aquathermal pressuring.