Studies On Mechanisms Of The Blocking In Oil Reservoirs By Polymer Flooding And Block Removal

During the oil production, injected water is frequently used to enhance oil recovery. In order to increase further the rate of production, non-conventional materials are introduced into the oil reservoirs, such as surfactant agent or polymer. The article described in detail the mechanism and current development of enhanced oil recovery, and analyzed emphatically the study on the polymer flooding, but the polymer flooding occurs lagging in the multi-pore medium through chemical adsorption and mechanical trap as a result of the reduction of flow cross-section of pore channel and increase of liquid flow resistance causes the oil reservoir blocking of injected polymer well, as well as the comments about varieties of technologies for removing the blocking. Based on the injection pressure increasing and the reservoir blocking which affected greatly the production in the polymer flooding well of No. 6 petroleum factory of Daqing Oil Field, The composition and structure of the locking materials from the well were analyzed by instrumental and chemical analysis. It was found that the main composition of blocking substances are polyacrlamide, sulphide, clay and mechanical impurity, and agglutinative core composition mostly are sulphide, iron oxide, oil and clay, etc, and the outside is winded by polyacrlamide. Then further matching simulation experiments verified that the decisive factors of the reservoir blockings are from iron sulphite and polyarclamide, which produce suspension or flocculent deposit that form blocking substances. It is effective for removing the blocking to choose chlorine dioxide as the best dissolving agent and combine a treatment of hydrochloric acid in accordance with the blocking factors of oil reservoirs and the experiments.