Design and Performance Prediction of an MEOR Field Pilot by Numerical Methods

This paper deals with the design and performance prediction of an MEOR field pilot by numerical methods. With MEOR, additional oil production is generated via a combination of various EOR mechanisms triggered through the growth of the microorganisms. Numerical modelling of MEOR performance is challenging mainly due to the complexity of describing the processes that take place in the reservoir. On top of that, the mathematical description of the transport of the microorganisms through oil bearing porous media is still to date only scarcely covered in literature. However, numerical evaluation is yet an inevitable part of a field application. Wintershall is conducting experimental and numerical studies on MEOR to establish it as a matured technology in a kind of tool-box concept for adding value to its assets. The technology developed so far will be tested in a pilot planned for one of Wintershall’s German oil fields within the next years. Numerical work is being performed via lumped as well as discretized models. The model of Bryant and Lockhart (2002) is used to describe the reaction engineering constraints in order to optimize the inoculation versus residence time. The reservoir nutrient logistics and the produced metabolite concentration are estimated based on conversion kinetics. The necessary input data are provided by growth curves obtained by feeding nutrients to defined microorganisms of the corresponding reservoir. The prediction of the production performance of the planned field pilot is performed by the numerical implementation established and validated by Wintershall using STARS/CMG as the supporting tool. The new MEOR model is calibrated with laboratory data including growth curves, measured metabolite properties and dynamic experiments, which are later up-scaled for the field pilot. The following EOR effects are considered: changes in both water and oil phase viscosities, decrease in IFT and bio-plugging. Sensitivity runs performed on a 5-spot injection pattern generic model of the field chosen for the pilot show that the dominating effect on additional oil recovery would be the flow diversion by the plugging preferential water injection paths through microbial growth. The simulation shows an additional oil recovery between 5 and 7% for the case studied. Bryant S. L., Lockhart P. T.(2002) Reservoir Engineering Analysis of MEOR, SPE Reservoir Evaluation & Engineering, February, 365-374.