Pilot test effect analysis of profile control for fractured low permeability reservoirs in northern Shaanxi

The Triassic Chang 6 reservoir in Ansai Oilfield is with low permeability((1~3)×10-3 μm2), and there are 29 oil wells with water breakthrough of fracture or fracture-pore type in 92 oil wells with water production. The average permeability of the Triassic Chang 4 and Chang 5 reservoir in Jing’an field is 1.447×10-3 μm2, and the produced water of 41 oil wells is injection water in 68 oil wells with water production. Some of the oil wells produced injection water at early time of production due to fracture communication. The average permeability of the Jurassic Yan 9 reservoir in Jiyuan field is 66.9×10-3 μm2, and the water intake thickness is only 35% of the total reservoir thickness. A part of the wells are watered out, whereas most of the oil wells have not take effect from water injection. Swelling particles and weak polymer gel were taken to conduct the profile control treatment. In the 20 profile control treated well groups, the injectivity coefficients of 19 well group were decreased significantly, 11 well groups obtained the effect of oil rate increase and water cut decrease, 5 well groups obtained water cut decrease, and 3 well groups was invalid for the profile control treatment due to too high crack sealing strength.