Development and Performance Evaluation of a High-Temperature Profile Control System

In the late stage of the steam flooding development of heavy oil reservoirs, the contradiction between layers is prominent, which makes the development of the reservoir difficult. To obtain a profile control agent suitable for steam flooding in heavy oil reservoirs, the modification technology was used to improve the temperature resistance of the traditional NH-1 main agent, as the conjugation effect may enhance the stability of the molecular structure. Thus, we obtained the modified NH-1 main agent, which was used in combination with graphite particles. To explore the oil displacement effect of the profile control system, the single-variable method was used to optimize the profile control system and evaluate its performance. Moreover, the multimedium steam flooding experiment was carried out to further verify the profile control capability of the profile control system. The results show that the formula of the graphite particle-gel compounding system is 0.03% coagulant BK-A05 + 2.2% cross-linking agent I + 1.8% cross-linking agent II + 6% modified NH-1 main agent (prepared by reacting NH-1 main agent with 65% concentrated nitric acid at a solid-liquid ratio of 1:6) + 0.7% graphite particles (10 000 meshes) + 0.3% suspending agent CMC. The gel viscosity of the profile control system can reach 2 × 10 6 mPa·s, the gel temperature range is wide (160-280 °C), and the temperature resistance is 300 °C. The profile control system has good injection performance, plugging effect, washing resistance, and thermal stability and is significantly better than the gel system alone. The experiment results also show that the profile control system has a strong profile control capability and expands the swept volume. The crude oil recovery increases by 8.89%, and it can be effectively applied to the profile control operation of heavy oil multimedium steam flooding.