泡沫驱微观驱油机理及驱油效果

Microscopic displacement mechanism and oil displacement effect of foam flooding

泡沫作为驱油介质具有调剖和驱油的双重机理,分别采用渗透率级差为1∶3的非均质微观模型和并联填砂管模型,研究泡沫的微观驱油和液流转向机理,评价其对驱油效率的影响。非均质微观模型驱替实验结果表明,泡沫驱存在混气水驱油、表面活性剂驱油和泡沫驱油3个显著渗流区。混气水驱油渗流区的形成是由于泡沫的不稳定消泡,气体与泡沫液析出,气体窜进所致。泡沫破灭所析出的泡沫液渗流滞后于气体并乳化原油,形成了表面活性剂驱油渗流区。混气水驱油和表面活性剂驱油能够降低残余油饱和度,使得后续注入的泡沫保持稳定,从而起到调驱作用形成泡沫驱油渗透区。非均质微观模型的高渗透条带在水驱、泡沫驱和后续水驱过程中,波及系数由52.4%先升至100%后降至74.3%,后续水驱波及面积减小且突破高渗透条带后,低渗透条带不再见效,说明泡沫驱时的封堵作用在后续水驱时存在有效期,有效期后封堵作用失效。并联填砂管驱替实验结果表明,分流率及驱油效率随着水驱、泡沫驱和后续水驱的变化规律与微观驱替机理分析结果相吻合,进一步验证了非均质微观模型驱替实验的结论。

As a oil displacement agent,the foam has dual mechanisms,including the profile control and oil displacement.The heterogeneous microscopic model with the permeability ratio of 1∶3 and the parallel sand-packed pipe model are used to study the microscopic mechanism of the oil displacement and fluid flow diversion of the foam,and to evaluate the effect on oil displacement efficiency.The results of the displacement experiments using the heterogeneous microscopic model show that there are three significant percolation zones for the foam flooding,including the mixed gas-water flooding,surfactant flooding and foam flooding.The formation of the mixed gas-water flooding zone is due to the unstable defoaming of the foam,gas separation from the foam liquid and gas channeling.The foam fluid precipitated by the bursting of the bubble flows behind the gas and emulsifies the crude oil,and then the surfactant flooding zone is formed.The mixed gas-water flooding and surfactant flooding can reduce the residual oil saturation and ensure subsequently injected foam stable to play a role in the profile control and oil displacement,and then the foam flooding zone is formed.In the process of water flooding,foam flooding and subsequent water flooding,the sweep efficiency of the high-permeability zone of the heterogeneous microscopic model is increased from 52.4%to 100%and then decreased to 74.3%.The low-permeability zone is no longer effective after the swept area of the subsequent water flooding decreases and breaks through into high permeability zones,which means that the plugging effect of the foam flooding has an effective plugging period in the subsequent water flooding,and there are no plugging effect after the effective plugging period.In the process of parallel sand-packed pipe displacement experiment with the same permeability ratio,the change of the fluid diversion rates and oil displacement efficiency with water flooding,foam flooding and subsequent water flooding is consistent with the result of the microscopic displacement mechanism analysis,which further verifies the results of the displacement experiment with the heterogeneous microscopic model.