Shales instability is a result of its mineralogical composition (especially content of different water sensitive clay) and its physico-chemical properties. In different laboratory research of shale/drilling fluid interaction conducted until now, researcher used different shale samples (original rock samples taken by the coring process, drilling cuttings, outcrop samples and artificial rock samples), different laboratory equipment and various inhibitive muds. There are two main problems related to the laboratory testing of shale samples’ quantity and quality. The main task of this paper was to examine the applicability of outcrop rock (shale) samples for laboratory research of shale/drilling fluid interaction. Rock samples were taken at natural shale outcrop on different locations in Croatia. In the first stage of the laboratory research, mineralogical composition and petrophysical properties of used shale samples were tested. In the second stage, shale samples’ swelling in different fluid were examined. After getting results of the shale swelling, new quantity of outcrop shale samples was taken, crushed to drilling cuttings size and placed in roller oven cells previous charged with different fluids. In the last stage, a dried (hot rolled) shale sample was used for preparation of the artificial shale samples. Generated artificial samples were used in further laboratory research.

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