Experimental Design for Evaluation of Formation Damage by Microbial Contamination in Water Flooding Processes. A Colombian Study Case

Abstract

Microbial contamination is well known in the oil and gas industry and it occurs in most processes where water processing systems are involved. Microorganisms are spread everywhere, even in the subsurface, where operations of oil exploration and production are developed. For this reason, different genera of microorganisms can affect the Oil & Gas Industry. One of the major problems in oil mature fields undergoing secondary recovery is the contamination with sulfate reducing bacteria (SRB), caused generally by the injection water system (fresh and/or production) and/or of the reservoir (natural or by drilling fluids, completion, stimulation, etc.). This problem causes formation damage and microbiological induced corrosion (MIC) in the injection-production system. In many producing wells, formation damage by microbiological contamination is initially masked by a decline in reservoir pressure; however, initial production of H2S does provide a possible microbial contamination of water production, water injection and eventually petroleum reservoir. In some producing wells, H2S concentrations have exceeded the lethal limits of 250 ppm and there are cases of producing wells with levels above 1000 ppm. In this work, both a conceptual study and an experimental protocol were developed for the evaluation of formation damage by microbial contamination in water flooding processes. It is focused on finding the best stimulation treatment with biocides to H2S and corrosion control in Producer Wells of Oil Fields Undergoing Secondary Recovery as part of the comprehensive strategy to implement in the injection-reservoir-production system of the Chichimene field in Colombia. This study included the following stages:1. State of the art to define main bactericides, matrix stimulation treatments to H2S and corrosion control, removal of biomass (biofilm) and iron sulfide, etc. in producers wells. 2. Conceptual study of the formation damage by growth of sulfate-reducing bacteria.3. Experimental protocol for the evaluation of formation damage due to microbial contamination in water flood processes.4. Experimental evaluation of formation damage due to microbial contamination in cores of the Chichimene field, in Colombia. Finally, the main findings, conclusions and recommendations obtained in this study are shown.Keywords: microbial contamination, microorganisms, secondary recovery, stimulation, formation damage, sulfate-reducing bacteria, water production, waterflooding.