Microbial Stimulation Treatment ofHigh Water-Cut Wells in the

Viola Formation, Pontotoc County, OK

D.R. Simpson, R. M. Knapp, N. Youssef, K.E. Duncan, M.J. McInerney, C. Brackin

Introduction• Post water-flooding, approximately 30% to 50% of the

original oil present remains entrapped by capillary forces • During microbial stimulation, a high water-cut well is injected

with beneficial bacterial culture in aqueous solution mixed with fermentable carbohydrate such as glucose or molasses and then purged in a “huff and puff” treatment.

• Microbial metabolites are produced in-situ such as biosurfactants, gases, acids and solvents to improve oil recovery.

• Mechanisms include interfacial tension reduction, reservoir pressurization, increase in porosity, viscosity reduction and wettability alteration

Introduction• In the summer of 2005, a series of 50-bbl injections of brine

mixed with nutrient (glucose, nitrate and trace metals) and two bacteria, Bacillus licheniformis RS-1 and Bacillus subtilis subsp. subtilis spizizenii NRRL B-23049, were conducted on wells producing from the same Viola formation in Pontotoc County, OK with encouraging results.

• As a result, in November 2007, we scaled-up the “huff and puff” treatments on the same wells to 500-bbl inoculums of brine mixed with the same nutrients and Bacillus species in order to determine whether the microbial process improved oil recovery.

Preparation for inoculation and nutrient amendment of 50 bbl starter culture

Filling and mixing of 50 bbl starter culture

Nutrient amendment for 2 x 500 bbl injections

Unloading of nutrient amendment

Pre-injection filling with pump truck and mixing with gasoline pump

Injection with gasoline pump

Oil spread assay to detect biosurfactant activity

WOR and % oil cut before and after stimulation

Figure 1: The total net increase in oil production from the Robertsonseparation tank battery

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Figure 2: The daily oil recovery from the Robertson separation tank battery

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Figure 3: Comparison of the daily oil recovery with the in-situ combined daily microbial metabolite recoveries for the Robertson separation tank battery

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crude oil lipopeptide X 100 alcohol acid glucose CO2

Figure 4: The time-course of WOR for Robertson 15 and 13 wellhead samples

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Figure 5: The time-course of percent oil cut for Robertson 15 and 13 wellhead samples

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Figure 6: The average daily production volumes for Robertson 15 and 13 wellhead samples

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Economic Analysis

• Total material/equipment expenses were $3000/well

• ~218 bbl net improvement in oil production from baseline in 129 days at a cost of $27.5/bbl

• $7080 profit realized assuming $60/bbl oil

Conclusions• Improved oil production• Decreased WOR and increased % oil cut • Detection of microbial growth and metabolic

products sufficient to mobilize crude oil• Initial economics encouraging• Optimization needed to increase biosurfactant

concentrations and reduce incremental cost of recovery

Acknowledgements

• Arrow Holding, Inc.– Marshall Brackin– Courtney Brackin

• DOE– DE-FC26-04NT15522

• Arrow-Wego Perforators– Stan Lemons

• Arrow Oil and Gas, Inc.– Steve McDaniels

• Surbec Environmental, LLC

• University of Oklahoma– Professor Roy Knapp– Professor Mike McInerney– Dr. Noha Youssef– Dr. Kathleen Duncan– Jim Davis– Sandra Weiland– Neil Wofford– Foluke Ajisafe