Cyclic steam stimulation is one of the important ways to develop heavy oil. In the past research, saturated steam and superheated steam were mainly used as injected fluids. With the advancement of technology, supercritical water cyclic steam stimulation began to receive more and more attention.
Thermodynamic oil recovery is the main way of heavy oil development, and supercritical water as a displacement medium for thermodynamic oil recovery has high pressure, high thermal enthalpy value and low density which makes it easy to spread in formation. At the same time, supercritical water also has some special properties, its polarity will reverse under high temperature and high pressure, which is beneficial to the mutual solubility of supercritical water and crude oil, increasing the efficiency of oil displacement.
In this paper, a cyclic steam stimulation model is presented for estimating recovery factors and production rates of different injection fluids, and the corresponding parameters are derived by a pilot field test. Firstly, a steam stimulation model using different injection fluids is proposed based on the properties of supercritical water, saturated and superheated steam. Secondly, according to the established model, the effect of the state of injected water on production rate and recovery factor of cyclic steam stimulation was studied. Thirdly, using supercritical water as the displacement medium, the effect of injection rate on production rate and recovery rate of cyclic steam stimulation was studied. Finally, the optimal production rate is obtained by analyzing the results.
Results show that: (a) Supercritical water can better heat the formation during steam stimulation than saturated and superheated steam. (b) Supercritical water has better injection capacity than saturated and superheated steam. (c) Cumulative oil production when injecting supercritical water is greater than the injection of saturated steam and superheated steam. (d) Cumulative oil production of supercritical water injection increases as injection rate rises. (e) The higher the injection rate is, the higher the production rate at the same production time.