Damage Mechanisms of Tight Sandstone Reservoirs Induced by Silicate Drilling Fluid

Silicate drilling fluid has good wellbore stability performance, but its damage mechanism to reservoirs is not well understood. This article focuses on tight sandstone reservoirs, conducting a series of experimental evaluations including the dynamic-static damage evaluation, fluid compatibility evaluation, surface performance testing, etc., to assess the extent of damage caused by silicate-based drilling fluid to the reservoir. Furthermore, SEM, energy spectrum analysis, mercury injection experiment and other methods are used to analyze the damage mechanism to the reservoir caused by the Silicate drilling fluid. The research results indicate that the invasion of silicate drilling fluid can enhance the hydrophilicity of tight sandstone reservoirs, increase the self-absorption capacity of the reservoir, and ultimately lead to serious water blockage damage; The high pH characteristic of silicate drilling fluid can lead to alkali corrosion reaction between filtrate and clay minerals, generate silicate precipitation to block the seepage channel; The SiO32−, CO32− and OH− in the filtrate of silicate drilling fluid react with Ca2+, Mg2+ and Al3+ in the formation water and rock pores, forming new mineral phases such as sodium albite and analcime to block the seepage channel; Alkali consumption and dilution by formation water can cause a decrease in the pH value of silicate drilling fluid, leading to induce the precipitation of gel containing silicate, which adsorb and retain on the rock surface causing damage to the reservoir; Hydrochloric acid can reduce the pH of silicate drilling fluid, and is prone to generating fluoride-containing precipitates, making it unsuitable for remedying the damage caused by silicate drilling fluid to tight sandstone reservoirs.