Abstract
MEOR, particularly indigenous MEOR technology, has been studied extensively in Dagang Oilfield, China, since early 1990s. Based on lab study results, pilot tests were conducted in four different reservoirs (in the Gangxi, Gangdong, Wang-guantun and Kongdian oilfields). In total 24 injection wells and 55 production wells were involved in tests with responses observed in 47 wells.
For MEOR, a series of microbial species, which were suitable to target reservoirs, were developed using produced fluids. The process included separation, culture, and special domestication, contributing to improved oil properties and producing surfactants, emulsion and gas. Core experiments in lab showed that, comparing to waterflooding, microbial flooding could increase the recovery rate by 6-8%. Field tests indicated the cumulative incremental oil production 28,000 tons from the reservoir at 54 to 73°C. One in the tested fields had already been flooded by polymer solution.
Considering the limitation of microbial species variability, match of culture with formation water, numerous of fermentation surface and injections, it was determined to develop indigenous MEOR. This process provided better effectiveness at 60°C. The test results showed improved ecosystem and increased oil production of over 31,000 tons with water cut decreased by 5% at average.
Our study and field tests for microbial flooding showed that reservoir temperature was the most important factor and then microbial nutrients and production pattern follow.
