Study on the Mechanism of the Action of HDD Drilling Fluid on the Mechanical Properties of Clay Stratum

After remodeling the sample, the drilling fluid was tested to determine the cations. The cation exchange capacity test determined the drilling fluid content after the experiment to study the evolution mechanism of the mechanical properties of drilling fluids before and after remodeling the clay formation samples from a macro and mesoscopic perspective. The correl function is used to analyze the correlation between the cation-related parameters of the drilling fluid and the pore and mechanical parameters of the remodeled sample. The results of water-based drilling fluid show that the correlation coefficient between the porosity of the remodeled sample and the cation exchange capacity of the drilling fluid and the free cation concentration in the solution is close to -1. That indicates that the cation exchange capacity and the free cation concentration in the solution are negatively correlated. After the experiment, the porosity of the reshaped sample decreased with increasing concentration, and the mechanical characteristics improved. The MRI scanning images show that: No. 3 water-based solid-phase drilling fluid has the best effect on the inhibition of hydration expansion and pore sealing of the remodeled sample, and the mechanical properties of the remodeled sample are more optimum.