Utilization of Indigenous Microflora in Permeability Profile Modification of Oil Bearing Formations
Authors: Vadie Alex A. , Stephens James O. , Brown Lewis R. 
Published: December 2007

A field trial was undertaken to demonstrate that waterflood sweep efficiency can be improved by restricting high permeability zones through the growth of in-situ microorganisms. The field chosen for this demonstration was the North Blowhorn Creek Unit (NBCU) situated in Lamar Co., AL, and is a fluvial dominated deltaic reservoir. During the nine-month planning and analysis phase of the project (Phase 1) two new wells in a previously unswept area of the reservoir were drilled. Live cores were collected and employed in laboratory tests to insure that the nutrient additions planned for the field test would indeed stimulate the in-situ microflora to grow. Selective plugging occurred in test core plugs and the blue-print for the field trials was designed from this laboratory data. The apparatus for adding the microbial nutrients to the injection water of test injectors was assembled on a skid. Four such units were built and installed.

The NBCU unit has a total of 32 producing wells and 20 injection wells out of which four 5-spot patterns were selected for test patterns (for nutrient injection) and four 5-spot patterns selected for control patterns (for comparative purposes). The inclusion of control patterns was deemed absolutely essential to the scientific integrity of the project and will be monitored throughout the 45-month duration of the field trial. This experimental design enables comparisons of results of test patterns with control patterns as well as with historical data. Two test patterns are receiving only inorganic nitrate and orthophosphate and two test patterns are receiving molasses in addition to the nitrate and orthophosphate. Chemical, microbiological, and petrophysical characteristics of produced fluids are being monitored in addition to conventional production data. Data on the responses of the reservoir to the injection of microbial nutrients which began in November 1994, will be presented.

Introduction

A project was designed to field demonstrate that a microbially enhanced oil recovery process (MEOR) will increase oil recovery from fluvial dominated deltaic oil reservoirs. The process involves stimulating the in-situ indigenous microbial population in the reservoir to grow in the more permeable zones, thus diverting flow to other areas of the reservoir, and, thereby increasing the efficiency of the waterflooding operation. The technology behind this project is based on experiments performed on live cores from different locations of the U. S. which demonstrated that oil bearing reservoirs have indigenous microbial populations and stimulations of the indigenous population did result in increased oil recovery.

A unitized oil field, North Blowhorn Creek Unit (NBCU) situated in Lamar Co, AL, was chosen for the field demonstration of this project. The five and one half year project is divided into three phases, Phase I, Planning and Analysis (9 months), Phase II, Implementation (45 months), and Phase III, Technology Transfer (12 months). This paper will report on the first 12 months of the field demonstration.

Background

Microbial enhanced oil recovery is the utilization of microorganisms to increase oil recovery from subterranean reservoirs.

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