缝洞型碳酸盐岩油藏注氮气泡沫可行性及影响因素

为了研究缝洞型碳酸盐岩油藏注氮气泡沫可行性及影响因素,研制了缝洞型碳酸盐岩油藏细观物理模型和宏观剖面可视化物理模型,可由细观到宏观对缝洞型油藏注泡沫可行性及其影响因素进行室内物理模拟。细观物理模型实验结果表明:水驱后,剩余油主要以封闭孔洞内剩余油、阁楼油、绕流油和油膜的形式存在;氮气泡沫能通过重力分异及阻力效应启动阁楼油与绕流油并剥离油膜。在宏观剖面可视化物理模型上进行了注泡沫影响因素研究。实验结果表明:在含油饱和度较低时,以低部位井注、高部位井采(低注高采)的方式注泡沫效果更好,注泡沫时机不宜过早,宜在充分水驱的基础上转注泡沫;底水能量过强则不利于注泡沫,同时存在一个最优的泡沫注入量。对于碳酸盐岩缝洞型油藏开采中后期,注泡沫开采能够有效维持高效开发,提高原油采收率。

Feasibility and influencing factors of nitrogen foam injection in fractured-cavity type carbonate reservoirs

Mesoscopic physical model and macroscopic visualized model were designed for the fractured-cavity type carbonate reservoirs. The laboratory physical simulation experiments were conducted to evaluate the feasibility and influencing factors of nitrogen foam injection in fractured-cavity reservoirs from mesoscopic to macroscopic perspectives. Experimental results of the mesoscopic model illustrate that the residual oil exists primarily in the form of residual oil in the closed caves, attic oil, by-pass oil and oil membrane in the confined pores after water flooding. The nitrogen foam is able to activate attic oil and by-pass oil and then strip oil membrane by gravitative differentiation and drag effect. The influencing factors of foam injection were studied using macroscopic visualized physical model. Experimental results indicate that in case of low oil saturation, a better effect can be achieved in foam injection by means of low positional flooding and high positional production (low flooding and high production). Besides, foam injection shall be appropriately conducted when sufficient water flooding is satisfied. The case of excessively strong bottom water energy is not conductive to foam injection, and meanwhile an optimal amount of foam injected exists. Experimental results show that foam injection can effectively maintain high-efficient development and improve crude oil recovery rate in the mid-late production period of fractured-cavity carbonate reservoirs.