Nitrogen foam injection technique and its application in reservoirs with high water cut

The nitrogen foam displacement fluid was developed to meet the demand for controlling water breakthrough in the reservoirs with high water cut in Daqing Sabei Oilfield.The oil-displacement test using three heterogeneous cores showed that the nitrogen foam injection technique could decrease the produced liquid ratio and water cut of high-permeability reservoirs more significantly than the polymer displacement method.The field test indicated that nitrogen foam displacement could control the breakthrough of injected water along the high-permeability zone effectively.As a result,the oil displacement efficiency could increase considerably.In fact,the content of water in the output fluid of the tested wells decreased from 93.9% to 90.2%.The output of oil increased by 16.4 tons,whereas the output of the produced fluid decreased by 41 tons per day.The accumulated output of oil is 3 486 tons in half a year.The oil production increase and the overall efficiency are significant,which suggests that nitrogen foam displacement fluid can enhance oil recovery of Daqing Sabei Oilfield effectively and has good prospect in oilfield application.