A Successful Field Test of Microbial EOR Process in Fuyu Oilfield, China

Abstract

Abstract This field test for Microbial EOR (MEOR) has been carried out in Fuyu oilfield, China since 19961,2. Waterflooding by a patterned flood has been applied for over 20 years and various measures to decrease high water cut has been discussed for long time. The objectives of this MEOR project are to increase oil production from a water-flooded reservoir and to evaluate ability of microorganism (CJF-002) screened in our study. CJF-002 has an ability of producing insoluble polymer metabolically feeding on nutrient. This metabolic process is considered to be useful on plugging high permeable zones to reduce water channeling. Prior to the injection test of CJF-002 into the reservoir, core-flooding tests were carried out in order to evaluate the magnitude of permeability reduction due to plugging by the insoluble polymer. In the field tests, the following three different approaches were conducted: –Huff-n-puff test (single cycle) at production wells (1999),–First microbial treatment at injection wells (2000), and–Modified microbial treatment at injection wells (2001). In huff-n-puff test, CJF-002 and molasses were injected into 6 production wells. Among them, 4 wells indicated oil production increase and water cut decrease4,5. Based on these positive results of huff-n-puff test, the first microbial treatments were conducted at injection wells. In these treatments, cell count of CJF-002 and concentration of insoluble polymer were measured at the injection manifold and production wells to evaluate the metabolic activity of CJF-002 by colony forming unit (CFU) method and HPLC. Moreover, well logging such as Reservoir Saturation Tool (RST) and Water Flow Logging (WFL) and tracer tests were conducted before and after the microbial treatment to evaluate the effect of insoluble polymer on injection profile modification. As a result, microbial propagation was observed, however, the effect of injection profile modification has not been developed. The major reason was considered to be that sufficient propagation of CJF-002 was prevented by predominant population of other microbes propagated in the injection pipeline. From the unsuccessful result in 2000, injection method of CJF-002 and molasses was modified to prevent a propagation of other microbes and the modified microbial treatment was carried out in 2001. As a result, oil production in the test area increased more than twice in volume and the effect of plugging the high permeable zones was suspected from the results of tracer tests and preliminary reservoir simulation study.