Microbial Enhanced Oil Recovery Field Pilot in a Waterflooded Reservoir H. Yonebayashi* and K. Ono*, Japan National Oil Corporation; H. Enomoto* and T. Chida*, Tohoku University, C-X. Hong, China Jilin Province Oilfield Administrative Bureau and K. Fujiwara, Kansai Research Institute

Abstract

Japan National Oil Corporation (JNOC) / Technology Research Center (TRC) has been studying the Microbial Enhanced Oil Recovery (MEOR) process which makes effective use of microorganism's metabolism since 1987. Now, JNOC/TRC is planning a field trial to advance our MEOR study to the next stage. This paper describes the feasibility study of the field test.

As a target of MEOR application, a shallow oil field in China which has been under waterflood for over 20 years has been selected. At first, the target reservoir was investigated and adaptabilities of TRC's microorganisms to the field were tested to select candidate microorganisms for injection. The tested TRC's microorganisms were E. cloacae TRC-322, B. subtilis TRC-4118, B. subtilis TRC-4 126, B. licheniform is TRC-18-2-a, B. licheniformis JF-2, B. licheniformis SP-018 and E.cloacae TU-7A which have been especially screened as effective gas, acid, surfactant and/or polymer producers through basic laboratory tests. In the former investigation of the reservoir, a new technique, Polymerase Chain Reaction (PCR) established in the sphere of gene engineering was applied to the study to make clear distinction among reservoir-originated microorganisms. Effects of reservoir conditions, namely, reservoir water, temperature, nutrient, additives and indigenous microorganisms in the reservoir, on the microbial growth and their metabolism were tested to select candidate microorganisms for the field application.

Finally, four microorganisms (i.e. TRC-322, TRC-4118, TRC-18-2-a and TU-7A) were selected for the field trial through these compatibility tests followed by flooding tests. Additional oil recovery amounted to approximately 15% of waterflood residual oil using TRC-322, TRC-4118 and TRC-18-2-a on the average.

The field trial will start in middle of 1997. The objectives in this test are two fold. One is to validate the laboratory results which have been accumulated. The other is to investigate most predominant microorganisms (i.e. most effective ones on oil recovery), most effective metabolites and/or cause of obstruction of microbial activity.

Introduction

The oil production from applications of various Improved Oil Recovery (IOR)/Enhanced Oil Recovery (EOR) processes has been increasing steadily with the exception of a short recess during 1992-1994. It appears that this upward trend of EOR oil production will continue in the future, because the current worldwide oil-requirements are increasing. Moreover, due to the rapid economic growth in Asia, it is anticipated that the oil-demands will rise substantially in this region. Hence, it is necessary to increase the oil production. The IOR/EOR processes are recognized as one of solutions to cope with such situation, because the discovery of new big oilfield is becoming rare in recent years. Therefore, the development of the IOR/EOR techniques (redevelopment and stimulation technologies) to produce additional oil must be boosted to supply the future oil-requirements. We recognize microbial EOR process to be one of the effective options among various IOR/EOR methods to redevelop the waterflooded reservoir. Therefore, research on MEOR has been conducted at JNOC/TRC. TRC's research is especially focused on the in-situ process, in which gas production increases pressure and swells oil, polymer production controls mobility and/or surfactant production decreases interfacial tension, TRC has been searching microorganisms which have useful abilities (i.e. surfactant polymer, gas and/or acid productivity) for oil recovery. Up to now, about 500 microorganisms have been gathered and many talented ones have been selected through screening. In addition, flooding experiments have been carried out to evaluate their effects on oil recovery using strains which yielded excellent results in laboratory tests. It was necessary for TRC's MEOR study to move the phase of research to a field application. P. 451^

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