Research On Compound Foam Assisted Steam Flooding Technology For Enhanced Recovery In Heavy Oil Reservoir

Steam flooding is an important measure applied to the development of heavy oil reservoirs.However,steam overlapping and steam channeling tend to occur in the process of steam injection,resulting in the decrease of steam utilization rate and inferior exploitation of heavy oil reservoirs and restricting the economic development of oil fields.To solve this problem,it is of great significance for the exploitation of heavy oil by steam flooding to look for a certain kind of plugging agent which is capable of withstanding high temperature and changing the steam profile and study its profile control effect and scope of action during the steam flooding of heavy oil.This research will make a great sense to develop heavy oil by steam flooding.Through literature research combined with oilfield application,five kinds of foaming agents with good temperature resistance were optimized in this thesis.First,the temperature resistance,salt tolerance and compatibility of formation water as well as the effect of gas-liquid ratio and concentration on the resistance factor were studied.Second,the screened foaming agents with good temperature resistance and stabilizers were compounded to further study,including compound foam system formulation optimization,performance evaluation and the optimal use of concentration.Third,the changes of pressure drop,temperature,recovery ratio and remaining oil saturation in a single steam flooding process were studied through a selfdesigned long-tube sand filling model.Under the conditions of original oil saturation of 60% and 80%,the compound foam system was used to study the effect of enhanced oil recovery,the variation of pressure drop,temperature,plugging effect,oil recovery and residual oil saturation in the process.Additionally,the action scope,profile control and plugging mechanism of the compound foam system were analyzed.The results show that the optimum formula of foaming agent is foaming agent: stabilizer = 4:1,concentration is 0.4%,gas-liquid ratio is 1:1,injection mode is slug,the resistance factor in the process of steam flooding is greater than 4.Under this condition,the compound foam system shows a relatively good profile control effect,effectively restrains steam channeling and increases recovery ratio of heavy oil.According to the research on the original oil saturation(80%,60%)of different oil reservoirs,when a single steam flooding is carried out,steam channeling is more likely to occur when the original oil saturation is 60%,and it is more effective to increase the oil recovery after plugging.Compound foam system can effectively reach the steam overlapping area.Furthermore,the effect of plugging near the injection end is better compared with the poor effect of plugging far from the injection end.