An Investigation on the Function of Mud Cakes on the Inhibition of Low Molecular Inhibitor for Water-Based Drilling Fluids

The major low molecular inhibitors showed inhibition in the hydration of clay in the laboratory for water-based drilling fluids, according to the principle of intercalation adsorption. However, inhibitors have failed and caused serious engineering accidents in drilling oil and natural gas. This paper investigated the transmission of several of drilling fluids to indicate whether low molecular inhibitor for drilling can effectively inhibit the wellbore hydration. The inhibition of drilling fluid with the plugging of mud cakes, was significantly weakened based on the hydration expansion of cores and cutting recoveries. The residual contents of inhibitors were determined with the precolumn derivation of high-performance liquid chromatography (HPLC) analysis and were chartered with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis in the structure of the derivative. The clogging behavior of the mud cake was described by environmental scanning electron microscopy (ESEM). Experiments show that 40 wt% to 90 wt% by weight of the corrosion inhibitor cannot pass through the mud cake in the dynamic filtration of the drilling fluid. The mud cake can be further divided into a nanostructure layer, a homogeneous layer and an anisotropic layer with different permeability. Most inhibitors should be limited to the nanostructure layer and the homogeneous layer.