The Study on the Influence of Temperature and Fluid Properties on the Interlayer Spacing of Illite Crystals

Illite is a typical layered silicate clay mineral commonly found in hard, brittle shale formations. During oil and gas drilling operations, drilling fluids undergo physicochemical reactions with illite, causing changes in crystal spacing. These changes affect the mechanical strength of the rock, leading to wellbore instability. This study uses X-ray diffraction (XRD) techniques to investigate the influence of different fluid concentrations, inhibitor types and temperatures on illite interlayer spacing. The results indicate that temperature is the most significant factor influencing changes in illite interlayer spacing within these experiments. In addition, the effects of different inhibitor types on illite interlayer spacing vary significantly. Ammonium chloride and potassium methylsilicon significantly reduce the door of illite, resulting in a contraction of the interlayer structure. This study reveals the mechanisms of fluid-illite interaction at the microscopic scale and provides important theoretical support for optimising drilling fluid systems and controlling well stability.