Optimization of Microbial Flooding in Carbonate Reservoirs

Up to date, several investigators have studied the possibility of using microorganism in improving oil recovery, but little work has been reported regarding optimization of the process. In the laboratory, bacteria have been shown to produce chemicals such as surfactant, acids, solvents, polymers, and gases (mainly CO₂:) that can significantly contribute to improving displacement and sweep efficiency. Some of these microorganisms can withstand the harsh environment of the oil field and grow at a substantial rate feeding on the organic matter and crude oil itself, thus leading to improvement of oil recovery. Moreover, the MEOR process is friendly to the environment. Several field trials have been reported that showed the potential of bacterial enhanced oil recovery (BEOR) in improving oil recovery. Because these microorganisms are living organism and their behavior is difficult to predict, therefore no attempt has been made to study the parameters that control the process performance. This has become the main objective of this work. In this work, we investigate the field parameters that affect the design a new process of Microbial Enhanced Oil Recovery in order to achieve optimum oil recovery. In order to reach this goal, the reservoir engineering factors that affect the recovery efficiency are defined first. These field parameters considered the most relevant and chosen for this study are the injected bacteria concentration, the adaptation time, the optimum slug size of bacteria solution, and the process application time. The capability of the microbes to transmit through a heterogeneous system and in long cores, and the effect of bacteria on rock wettability are also investigated.