【作者】 赵宁；

【导师】 王业飞；

【作者基本信息】 中国石油大学(华东) ， 油气田开发工程， 2021， 硕士

【摘要】 低渗透油藏在满足中国的能源需求方面发挥着重要作用,但是低渗油藏由于低孔低渗、强非均质性、强敏感性等特点,水驱采收率低,注气/水过程中容易造成窜流。泡沫作为一种有效的调剖体系已在常规油藏得到广泛的应用,但在低渗油藏中,一方面,由于聚合物组分难以注入,传统的聚合物强化泡沫体系难以适用;另一方面,微气泡(指直径介于1-100μm的气泡)作为一种新的泡沫体系,其可以在有效防止气窜的同时进一步提高水驱后采收率,将微气泡应用于低渗油藏越发受到重视。据此,本文首先从产泡方式、起泡剂、稳泡剂筛选出发,构筑了一种直径在微米级别的微气泡驱油体系;然后通过微米管中的气泡稳定性评价以及岩心模型中的渗流与调剖实验,考察了微气泡体系在岩心孔喉中的稳定性、调剖能力;最后,借助微观可视化模型、单管和双管并联模型,研究了微气泡体系对低渗油藏的驱油特征和非均质适应性。研究结果表明:(1)多孔介质剪切法较传统的高速搅拌法相比是产生微气泡的较好方法;为避免通过添加聚合物等稳泡剂来强化微气泡所导致的注入性差等不利影响,本文采用不含稳泡剂的起泡体系。(2)稳定性和渗流实验研究发现,通过多孔介质剪切法可以得到气泡直径分布比较均匀而且不存在Plateau边界的稀微气泡体系;微气泡在体相中全部破灭的时间为91 min,但是在微米管和多孔介质中都至少可以存在455 min,可见微气泡在微米管中和多孔介质中的稳定性远大于其在体相中的稳定性;孔隙介质中,微气泡直径与岩心孔喉之间具有明显的关联性,而且微气泡仅需运移较短距离就可以达到直径与岩心孔喉直径相适应的效果,即微气泡极易与岩心孔喉相匹配;封堵实验表明,渗透率越低,微气泡残余阻力系数相对于阻力系数的保留率越高,封堵效果越好;调剖效果方面,微气泡可以动用的极限渗透率级差为245.3,可以在较宽的非均质范围内起到调剖效果。(3)驱油研究表明,在均质条件下,随着岩心渗透率的降低,微气泡驱及后续水驱采收率越来越高,微气泡可以将低渗岩心采收率提高27.8%以上;而对非均质条件,渗透率级差小于11.9时,微气泡可以提高低渗岩心的采收率,超过该范围,微气泡调剖驱油能力显著减弱。更多还原

【Abstract】 Low permeability reservoirs play an important role in meeting China’s energy needs,however,due to the characteristics of low porosity,low permeability,strong heterogeneity,and strong sensitivity in low permeability reservoirs,the oil recovery of water flooding was low,and crossflow was easy to cause during gas/water flooding.Foam has been widely used as an effective profile control system in conventional reservoirs,but in low permeability reservoirs,on the one hand,because the polymer component was difficult to inject,traditional polymer reinforced foam system was difficult to apply;On the other hand,microbubbles(referring to bubbles with a diameter between 1-100 μm)is a new foam system,they can prevent gas migration and further improve the oil recovery after water flooding,therefore,the application of microbubbles to low permeability reservoirs to improve oil recovery is getting more and more attention.Based on this,a microbubble flooding system with a diameter of micrometer was firstly constructed from the screening of bubble production method,bubble generating agent and stabilizing agent.Then through the bubble stability in the microtube,the seepage and profile control experiments in the core model,the stability and profile control ability of the microbubble system in the core throats were investigated.Finally,with the aid of microscopic visualization model,single and double tube parallel models,the oil displacement characteristics and heterogeneous adaptability of the microbubble system were studied.The research showed:(1)Porous media shearing method was a better method to generate microbubbles than high-speed stirring method;In order to avoid the adverse effects of poor injection caused by the addition of foam stabilizers such as polymers to strengthen microbubbles,this article adopts a foaming system without foam stabilizers(2)Stability and seepage experimental research showed,a dilute microbubble system with uniform bubble diameter distribution and no Plateau boundary was obtained by the porous medium shear method;The microbubbles all broke up in the bulk phase in 91 min,but could be exist for at least 455 min in both the microtubes and the porous medium,indicating that the stability of the microbubbles in the microtubes and the porous medium were much greater than their stability in the bulk phase;In the porous media,there was a clear correlation between the microbubbles generated in porous media and the core hole roar.The microbubbles only need to transport a short distance to achieve a effect that the diameter was compatible with the pore throat of the rock,that is,the microbubbles were easily matched to the rock;Seepage experiments with microbubbles showed that the lower the permeability,the higher the retention of the residual resistance coefficient relative to the resistance coefficient and the better the plugging effect;Profile control effect,the limit permeability contrast that the microbubbles can use was 245.3,microbubbles can play a profile control effect in a wide range of heterogeneity.(3)Displacement research showed,under homogeneous conditions,with the decrease of core permeability,the oil recovery of microbubble flooding and subsequent waterflooding were getting higher and higher.Microbubbles can increase the oil recovery of low permeability cores by more than 27.8%;Under heterogeneous conditions,when the permeability contrast was 11.9and below,microbubbles can improve the recovery of low permeability cores.If the range was exceeded,the microbubbles profile control and oil displacement capability would be significantly weakened.更多还原