Current situation and development direction of upward and downward return mechanical plugging technology for chemical flooding in Daqing Oilfield

The upward and downward return plugging technology is the main means to facilitate chemical flooding into the stimulation layers, and among which, the mechanical plugging technology is the most commonly used technique. The application scope and technical characteristics of various mechanical plugging technologies applied in the field varies, and the plugging performance is also quite different. Therefore, this paper analyzes the upward and downward return mechanical plugging technologies used in Daqing Oilfield, introduces the mechanical plugging technologies such as upward return plugging drillable bridge plugs, slip-hanging packers, injection-plugging integration and expandable pipes, as well as the mechanical plugging technologies of downward return for injection wells and production wells, and analyzes the advantages and disadvantages of different technologies. The following conclusions are drawn: the plugging performance of drillable bridge plugs is reliable and can meet the current requirements of upward return plugging; the integrated injection-plugging technology is not yet mature; the slip-hanging packers and expandable pipes can be used as a limited supplement to the upward return plugging technology; the bridge-type double-pipe cross-layer plugging technology has obvious advantages in reliability, and should be used as the main technology for the downward return plugging of the injection wells. The existing downward return plugging technology of production wells, combined with the sealing verification technology, can meet the needs of downward return plugging of production wells. It is recommended to carry out the research on the mechanical plugging technology and accurate channeling detection technology used in wells with casing deformation in the next step to ensure the plugging performance and reduce the plugging cost. Besides, a unified and standardized plugging technology system should be established to form a plugging technology selection chart to guide the plugging technology selection.