Evaluation of the Inhibiting Effect of Drilling Fluid on Shale Hydration Based on Acoustictime

摘要

Acoustic time is the reflection of mechanical strength of rock. The study on shale hydration based on acoustic time can reflect the metabolic feature of strength and stability of borehole wall and shale. A series of hydration and acoustic wave experiments are carried to study the process of shale hydration and the inhibiting effect of drilling fluid on shale hydration, the result showed: (1) The hydration level when shale contact with drilling fluid is mutually related to the variation of intercrystalline distance. The result of hydration increase the intercrystalline distance of shale, which provide theoretical foundation for evaluating the hydration level by acoustic time. (2) When shale contact with incompatible drilling fluid, volume swelling is visual macroscopically, the acoustic time value is increased as the increasing of hydration time, so the hydration swelling level can be evaluated based on acoustic time. (3) The acoustic time of shale samples which immersed in inhibitive mud generally decreased, the variation of acoustic time reflect the inhibiting effect of drilling fluid on shale hydration, which provide significant theoretical foundation for making drilling program effectively.