Microbial field pilot study. Final report

Abstract

A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of i, bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. Bythe end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one ha.lr barrels (13.1 m3) of tertiary oil have been recovered. Microbial activity has increased CO2 content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

Microbial field pilot study

“…This extended the simulation study performed under the previous study (Knapp, et al, 1989). The overall history match was within 5% of observed data.…”

“…The Microbial Field Pilot Study began as a 15 month project to determine whether a microbially enhanced oil recovery process was feasible in the hypersaline oil reservoir, Southeast Vassar Vertz Sand Unit (SEVVSU) (Knapp, et al, 1989). Previous laboratory studies utilized bacteria at 8% salt content or less.…”

“…Since 1979, 33 papers, seven Master's theses, and three Doctoral dissertations have been produced at the University of Oklahoma. Planning, experimentation, and reservoir characterization in preparation for the project described in this report were performed under a previous contract (Knapp, et al, 1989).…”

Pretest studies for a microbially enhanced oil recovery field pilot in a hypersaline oil reservoir

“…The geological and petrophysical characteristics of the reservoir were described previously (Knapp, Mclnerney, Menzie, et al, 1989). The depth of the reservoir is 550 m, the temperature is 33°C, and the original pressure was 6020 kPa.…”

“…The Vertz sandstone belongs to the Wabaunsee group of Pennsylvanian age and is a uniform well-ordered sandstone. Geological studies (Knapp, Mclnerney, Menzie, et al, 1989) indicated that the reservoir was formed by a braided stream depositional system, has porosities ranging from 18 to 24%, and has permeabilities ranging from 100 to 500 mD (0.1-0.5 /zm 2 ).…”