Research Of Mechanical Water Plugging Pipe Strings

Heavy oil reservoirs are the main part of the reservoirs of Liaohe Oilfield. And most of the recovered blocks are heavy oil blocks, in which the development of the super heavy oil reservoirs of Shuguang Oil Plant have entered the later stage of huff and puff. Due to huff and puff pressure-reducing recovery with long-term multicycles of water injection and steam injection, serious formation water production, serious damage of the casing compensator at the top of the formation and the damage and leakage of the casings, water cut of oil wells has increased sharply, water flowing backward into the formation has occurred frequently and finally normal production of oil wells has been influenced. Meanwhile, more and more casings have been deformed. Those deformed casings couldn’t pass through conventional downhole tools and current casing-deformation packers couldn’t meet the temperature requirement of the production. In this case, it is difficult to apply the technique of mechanical water plugging in most of the higher water cut oil wells and their recovery will also be affected. In this paper, the technique of mechanical water plugging pipe strings based on super heavy oil wells was presented. Principles, structures and deformations of pipe strings of 7" casing wells, 5" casing wells and 7" casing deformation wells have been studied and optimized to improve the stimulation methods of super heavy oil wells and increase the ultimate recovery of these wells.Mechanical water plugging of super heavy oil wells have been applied for more than 150 well times from 2009 to 2012 with cumulative incremental oil of 44100 t, in which general water plugging for more than 50 well times with success ratio of 100% and cumulative incremental oil of 14303 t, mechanical water plugging with fluid mixing for more than 90 well times with success ratio of 100% and cumulative incremental oil of 29137 t and mechanical water plugging of casing deformation wells for 3 well times with success ratio of 100% and cumulative incremental oil of 660 t. This technique has met the actual production requirements of super heavy oil wells and played an important role in the production of super heavy oil and great economic and social benefits have been obtained. Successful research of mechanical water plugging of super heavy oil wells is helpful to the conventional production and later recovery of super heavy oil wells of Liaohe Oilfield.