The Utilization of the Microflora Indigenous to and Present in Oil-Bearing Formations to Selectively Plug the More Porous Zones Thereby Increasing Oil Recovery During Waterflooding

This project is a field demonstration of the ability of in-situ indigenous microorganisms in the North Blowhorn Creek Oil Field to reduce the flow of injection water in the more permeable zones of the reservoir, thereby diverting flow to other areas thus increasing the efficiency of the waterflood. The project is divided into three phases-Planning and Analysis (9 months), Implementation (45 months), and Technology Transfer (12 months). This report covers the fourth year of work on the project. During Phase I, cores were obtained from a newly drilled well and employed in laboratory core flood experiments to formulate the schedule and amounts of nutrients to be used in the field demonstration. The field demonstration involves injecting potassium nitrate, sodium dihydrogen phosphate, and in some cases molasses, into four injector wells (Test) and monitoring the performance of surrounding producer wells. For comparative purposes, the producer wells surrounding four untreated injector wells (Control) also were monitored. Twenty-two months after the injection of nutrients into the reservoir began, three wells were drilled and cores taken therefrom were analyzed. Nitrate ions were found in cores from all three wells and cores from two of these wells also contained phosphate ions- thus demonstrating that the injected nutrients were being distributed widely in the reservoir. Microorganisms were shown to be present in cores from all three wells by cultural methods and by electron microscopy. In some sections of the cores, the number of microbes was large. Oil production volumes and water:oil ratios (WOR) of produced fluids have shown clearly that the MEOR treatment being demonstrated in this project is improving oil recovery. Of the 15 producer wells in the test patterns, seven have responded positively to the injection of microbial nutrients into the reservoir, while all eight of the producer wells only in control patterns have continued their natural decline in oil production, although one well did have some improvement in oil production due to increased water injection into a nearby injector well. Two of the wells have been abandoned because of uneconomical production. In light of these positive findings and with DOE�s approval, the scope of the field demonstration was expanded in July 1997 to include six new injector wells. Two of these wells were previously control injectors while the other four injectors were not included in the original program. Of interest has been the performance of two wells in what was formerly a control pattern. Since the injector in this pattern (formerly Control Pattern 2) began receiving nutrients, two of the wells in the pattern have shown improved oil production for the last three months. While it would be premature to definitely characterize these two wells as yielding a positive response, these early results are certainly encouraging. Of special significance is the fact that over 7953 m (50,022 barrels) of incremental oil have been 3 recovered as a result of the MEOR treatment. Further, calculations show that the economic life of the field will be extended until July 2004 instead of a previously anticipated closure in Dec. 2002. This finding is particularly impressive in view of the fact that only four of the twenty injector wells in the field were treated during the first 30 months of the project. Preliminary indications are that byincreasing the number of injector wells pumping microbial nutrients into the reservoir from four to ten, more oil will be recovered and the economic life of the field will be extended even further. It should be emphasized that the above calculations do not take into account the oil being recovered from the five new wells that were drilled during the course of this project