Determine, through experiments and computer simulation, the best design and evaluation of a combined microbial/surfactant-polymer system for improved oil recovery.

Program
This project was selected as a Historic Black College and Universities non-competitive award.

Prairie View A&M University
Prairie View, TX

Many domestic oil fields are facing abandonment, although they still contain two thirds of their original oil. A significant number of these fields can yield additional oil using AOR techniques. Yet many independent producers do not have the capital to implement costly advanced recovery programs. Marginal wells are desperately in need of inexpensive AOR technologies to extend the life of oil and gas reservoirs with unrecoverable reserves and prevent premature abandonment. Microbial enhanced oil recovery (MEOR) technologies have become established as cost-effective solutions for declining oil production.

Project Results
The research conducted indicated that the improved recovery efficiency for different nutrients appeared to be related to population numbers and not to different recovery mechanisms. High surfactant production is the main recovery mechanism during the NIPER 1A recovery experiments, while improved sweep efficiency is the main recovery mechanism during the NIPER 11 experiments. These conclusions are supported by low surface tension values during the NIPER 1A experiments and high viscosity during the NIPER 11 experiments. It was concluded that mixed microbial cultures hold more promise than single microbial cultures.

Benefits
A microbial advanced oil recovery (AOR) technique could cost-effectively increase oil recovery from mature domestic fields.

Project Summary
Among the project highlights:

• An extensive literature review of MEOR techniques was completed in conjunction with experimental work done in support of Task 1. An agreement was signed between Acorn Biotechnical and Bio-Engineering International Inc (BEI) in which Acorn received the lyophilized bacterial cultures produced by BEI and determined if they were viable and under what conditions they could be grown. The following cultures were shipped and were able to be revived: NIPER 1A, NIPER 6, NIPER 7, and NIPER 11A. NIPER 1A and NIPER 11 are the microorganisms most relevant to the study.
• All of the microorganisms listed were grown under different conditions in different media. A broth, Brewer Thyoglycolate by Difco, was selected as the most suitable medium to grow and maintain the organisms. This broth contains meat extract and sucrose as the principle nutrients, as well as phosphorus and nitrogen compounds. Good growth was obtained under anaerobic or oxygen limiting conditions. The growth under aerobic conditions was significantly less and in some strains almost negligible. The other two nutrients used were sucrose peptone broth and tryptic soy broth.
• NIPER 11A was observed to be limited to a salinity range of 0-4 wt % NaCl, with an upper temperature limit of 35 C. This microbial system can tolerate a pH range of 4.5-8.0. Other microbial strains were observed to tolerate a salinity up to 14 wt % NaCl, when grown in tryptic soy broth, and up to 5 wt % when grown in sucrose peptone broth. Their upper temperature limit was 45 C., with a pH tolerance from 6.0 to 10.0. These will be useful for a wider variety of reservoir conditions.

The emphasis of this work is on the design and evaluation of a combined microbial/surfactant-polymer system for AOR. The surfactant-polymer system will utilize bacteria that are capable of both bio-surfactant and bipolymer production. Change in the microbial feeding nutrients was expected to produce the change from surfactant to biopolymer production. It was found, however, that two separate microorganisms are needed to produce surfactant and polymer.

Laboratory experiments were done using different carbon sources in order to determine if the microorganisms respond differently to different nutrients. Microbial samples grown for two months were transferred to flasks with different carbon sources. Weekly samples were withdrawn and colonies counted. Surface tension and viscosity was measured.

Experiments in multi-layer sandpacks were performed. The different layers were injected with one pore volume of different broths inoculated with the appropriate microorganisms. This injection was done at a low flow rate (1 foot per day). The sandpack was closed for 6 days to allow growth and chemical production (surfactant/polymer). After the shut-in period, the sandpack was opened and waterflooded. The fluids were collected, and the final oil saturation determined from mass balance.

(August 2005)
The project is in the final stages of completion.

$199,273

$0

NETL - Sue Mehlhoff (sue.mehlhoff@netl.doe.gov or 918-699-2044 )
Prairie View - Jorge Gabitto (jgabitto@andrew.cea.pvamu.edu or 936857-2427)