OPTIMIZATION OF DRILLING FLUID PARAMETERS USED IN THE PROCESS OF CORE SAMPLING FROM FORMATIONS

Abstract

This study examines the parameters of drilling fluids used in formation coring as a system of factors that determine core quality. The aim is to substantiate the relationship between drilling fluid parameters and the degree to which the native properties of core samples are preserved, and to identify directions for improving coring fluids. Systems analysis, comparative analysis, and cause-and-effect mapping were applied. Filtrate invasion, solids plugging, clay swelling, wettability alteration, core erosion, and core jamming in the inner barrel were identified as the principal mechanisms affecting core quality. Each mechanism was linked to measurable parameters, including density, plastic viscosity, yield point, API and HTHP fluid loss, filter-cake thickness, solids content, and lubricity. Low-solids polymer systems, sized calcium carbonate bridging agents, clay inhibitors, and minimized overbalance are proposed as the main directions for improving coring fluids. The scientific novelty lies in representing the drilling fluid–core–formation system as a single matrix linking the damage mechanism, the controlled parameter, and the technological solution. The proposed approach provides a methodological basis for subsequent laboratory and field testing.