Evaluating the Impact of Drilling Fluids on Sand Production and Mechanical Integrity of Clastic Reservoir

This study investigates the effect of drilling fluids on the sanding potential of weak clastic reservoir sandstone formations. The primary objectives are to evaluate the mechanical integrity of reservoir rock after exposure to different drilling fluids and quantify the changes in sanding potential under simulated reservoir conditions. Core samples from weak clastic reservoir were subjected to advanced thick-wall cylinder (ATWC) tests under controlled conditions of temperature (250°F), pore pressure (500 psi), and confining pressure (3000 psi). Dry samples were compared against those exposed to three different types of drilling fluids (DF1, DF2, and DF3). The physical and mechanical properties, including density, porosity, permeability, and mineralogical composition, were analyzed using XRD, XRF, and rheological data of the drilling fluids. The study revealed a significant reduction in ATWC strength for samples exposed to drilling fluids compared to dry samples. For example, sample from study field exhibited a 17.24% reduction in ATWC when exposed to DF1. Variations in porosity and permeability were also observed, with exposed samples generally showing reduced permeability and increased density. Mineralogical analysis identified quartz as the dominant component, with minor variations in other minerals between dry and exposed conditions. Exposure to drilling fluids reduces the sanding resistance of clastic reservoir rocks, which could influence wellbore stability and production efficiency. The degree of strength loss varies depending on the drilling fluid type and reservoir conditions, necessitating careful selection of drilling fluids to mitigate sanding risks. This study provides a comprehensive framework to understand and quantify the impact of drilling fluids on the mechanical integrity of sandstone reservoirs. The integration of mineralogical, mechanical, and rheological data offers new insights into optimizing drilling fluid formulations to enhance wellbore stability and reduce operational risks.