Effect of Wettability and Interfacial Tension on Microbial Improved Oil Recovery with Rhodococcus sp 094

Abstract

Abstract Results of coreflooding experiments with Rhodococcus sp. 094 species have already revealed that the bacterium is able to increase oil recoveries up to 9 %. Subsequent investigations have been carried out in order to recognize the complex mechanisms. Although published results proposed wettability changes in core plugs and favourable changes in the flow pattern as the active mechanisms but the potential of interfacial tension (IFT) and contact angle parameters was not fully understood in an aerobic process. The present paper is a continuation of a series of laboratory experiments and consists of interfacial tension and contact angle measurements by an automated pendant drop goniometer. A refined hydrocarbon as the drop and two variants of bacteria suspended in brine as the continuous phase were employed. IFT and contact angle experiments were conducted in a static and a dynamic condition and quartz plates with two initial wettabilities were used. A certain volume of the bacterial solution and a short observation time is used in the static condition and the measurements show that by using bacteria, IFT is lowered from 18.3 mN/m (brine) to 13.6 mN/m (bacteria) and the contact angle changes slightly. However, our hypothesis is that the bacteria are capable of forming very stable emulsions of oil in brine and the real IFT value is much lower and the contact angle changes significantly. In the static condition, metabolic activities that lead to reduction of interfacial tension or contact angle changes are stopped due to the lack of nutrients and oxygen during the short observation period. Therefore a constant flow of fresh bacterial suspension with enough nutrients and oxygen is ensured in the dynamic status. The IFT and the contact angle values obtained are presented in both conditions. The results show that the interfacial tension in the case of continuous flow of fresh bacteria is close to 5 mN/m. It is also observed that the contact angle is lower in the dynamic system compared to the static system. The new experimental procedure is more suitable for investigation of IFT reduction mechanisms in aerobic microbial improved oil recovery processes.