Investigating different fluids and injection patterns on the effect of reservoir rock quality alteration due to swelling and migration of clay minerals at carbonate reservoirs

Abstract

Nowadays, with the progress in technology, the demand for fossil fuels has increased. Therefore, improving the oil recovery from the current oil reservoir is among the crucial issues. Formation damage is a well-recognized subject that causes a reduction in the productivity or injectivity of an oil well. Reducing or controlling formation damage can be effective in improving oil recovery. There are various mechanisms that cause formation damage such as fine migration and clay swelling. In this study, the simultaneous effect of fine migration and swelling on the permeability of a carbonate rock was investigated. Kaolinite and smectite(bentonite) minerals were selected as the representative case for migration and swelling, respectively. Primarily, bottle tests were conducted to study the effect of different fluids on the swelling potential of the kaolinite and smectite. According to the structural feature of the kaolinite, it has the smallest cation exchange capacity (CEC) and consequently a low swelling tendency. Therefore, it showed negligible swelling in the presence of all fluids. According to the high cation concentration of the formation water (FW) and seawater (SW), smectite did not show a high swelling effect. However, diluting the FW and SW increased the swelling tendency of the bentonite. Nanoparticles were not able to control the swelling of the bentonite according to their larger size than the spacing of clay layers. Zirconium Oxychloride was also utilized as the swelling inhibitor which showed high efficiency. Eventually, different injection scenarios were tried using synthetic carbonate core samples with specific clay contents, and the best injection plan for formation damage control was determined.