The Effect of Water Saturation on Brittleness of Synthetic Shale with Different Diagenetic Pressure

During the exploration and development of shale gas, one of the most important factors that affect hydraulic fracture propagation is the brittleness of shale. Shale brittleness is affected by many factors, including water content,mineralogy compositions,temperature and so on. In this study, Ultrasonic measurements were performed to investigate the effect of water saturation on brittleness of a set of synthetic shale samples. In order to reduce the number of unknown factors caused by multiple minerals, we made 6 samples each with a different diagenetic pressure: 25MPa, 50MPa, 75MPa, 100MPa, 125MPa, 150MPa, named A1–A6. The results show that synthetic shale with larger diagenetic pressure shows higher Young’s modulus, lower Poisson’s ratio and higher brittleness. In the water saturation case, Young’s modulus decreases slightly compared to that of dry samples, but Poisson’s ration increases significantly. Poisson’s ratio is more sensitive to water compared with Young’s modulus. Water saturation leads to brittleness of samples significant reduction. The effect of water saturation on elastic properties of synthetic shale varies with directions, and the difference is related to the diagenetic pressure.