Strong-lipophilic and weak-hydrophilic viscosity reducers for ultra heavy oil in Fengcheng Block

In middle and late stages of ultra heavy oil development through steam huff-and-puff in Fengcheng Block, performances are poor under low temperatures. Accordingly, active macromolecular viscosity reducers are often selected to assist the steam huff-andpuff operations. Depending on specific properties (including contents of gel and asphalts) of ultra heavy oil in Fengcheng Block, stronglipophilic and weak-hydrophilic active macromolecular viscosity reducers were prepared. They were assessed in lab for simulated steam huff-and-puff operations. The test results show that the O/W viscosity-reducing system with viscosity reducer of 0.2% and oil/water mass ratio of 10?3 has an initial apparent viscosity less than 300 mPa·s. The system displayed static stability. The viscosity reducer can endure high temperature up to 300℃ and have good compatibility with de-emulsifier TA1031. Field tests show that oil production in the test is 40.38 t higher than, or 2.27 times of, that in the preceding round, under temperatures below 60℃. It is suggested that the active macromolecular viscosity reducers can dramatically reduce apparent viscosity of ultra heavy oil in Fengcheng Block. These reducers can effectively enhance mobility of ultra heavy oil under low temperatures and prolong low-temperature production time of steam huff-andpuff operations to enhance oilfield productivity. These reducers are prospective for application in oilfields.