An Integrated German MEOR Project, Update: Risk Management and Huff'n Puff Design

Abstract

Abstract This paper provides an update on a microbial enhanced oil recovery (MEOR) project conducted by Wintershall and BASF. Overall nutrient development and planning of a single well field trial (huff'n'puff, HnP) including risk management are described. A nutrient solution is tailored to stimulate growth and metabolite production of a reservoir community of various indigenous microbial species in a Wintershall operated oil field with challenging reservoir characteristics, including high salinity (160,000 ppm). Up-scaled imbibition experiments performed with sandstone cores using MEOR-oil systems are compared with injection brine-oil systems and assessed for the implications on incremental oil. The results of sandpack and coreflood experiments performed with optimized nutrient solutions are discussed regarding incremental oil recovery and responsible EOR mechanisms. A MEOR modelling concept developed using STARS/CMG is used to estimate additional oil production under various feeding strategies after the calibration of the EOR mechanisms assigned. As the laboratory and numerical works have indicated the feasibility of the MEOR field application, emphasis has been put on risk issues ranked in the register of the project. The key risk is potential souring of the reservoir due to the activation of the sulphate reducing bacteria (SRB) growing on the metabolites generated by the MEOR target community. Conventional mitigation measures have been tested in short and long-term experiments. An innovative solution had been developed to assure H2S free application without any consequences to the reservoir and to the MEOR application. A single well pilot application is planned in a pre-selected well of the Wintershall field studied with two main objectives: (1) proof of the concept of risk mitigation and (2) stimulation of growth and metabolite production. Identification of operational issues as well as data gathering to improve the forecasting methods towards full-field predictions are secondary objectives. A monitoring plan has been initiated to establish a baseline in terms of microbiological and petro-dynamic parameters. Temperature and volumetric distributions have been predicted based on the results of an injectivity test performed in the well. The data is used to design the HnP operation and the surface setup for the injection rate of 100 m3/day nutrient solution under well-defined conditions.