超低渗透储层注水吞吐微观油水运移特征

Micro-Scale Oil and Water Migration Characteristics of Water-Injection Huff and Puff in Ultra-Low Permeability Reservoirs

注水吞吐已经成为国内开发超低渗透油藏的重要技术之一。为探索超低渗油藏注水吞吐过程中油水运移特征,利用南泥湾长6储层天然岩心与模拟填砂管模型,测试了时间与压力对吞吐效果的影响,开展了注水吞吐动态渗吸的作用范围与微观动用特征的研究。分析发现:第一轮和第三轮吞吐效果随着闷井时间的增加越来越好,但第二轮吞吐效果逐渐变差,闷井压力的增加可以促进吞吐效果。动态渗吸作用范围与渗吸时间呈现正相关关系,含油饱和度变化差值随渗吸距离增加而逐渐减小。渗透率、孔隙尺寸影响吞吐过程中水的波及与大小孔道中原油的二次运移,开发实践中应尽量扩大注入水的波及范围,同时也需要重视不同孔径孔隙中发生的油水二次运移。

Water injection huff and puff has become one of the key technologies for developing ultra-low permeability reservoirs in China. To understand the characteristics of oil and water migration in the process of water-injection huff and puff in ultra-low permeability reservoirs,the influence of time and pressure on the huff and puff effect was tested using the natural core of Chang6 reservoir in Nanniwan and the simulated sand pack tube model,and the affected range and micro fluid migration characteristics of dynamic imbibition of water-injection huff and puff was investigated. The analysis found that the effect of the first and the third cycles of huff and puff got better with increase of the time of shut-in,but the effect of the second cycle of huff and puff got worse,while the increase of shut-in pressure led to enhanced huff and puff effect. The range of dynamic imbibition positively correlates with the imbibition time. The difference of oil saturation changes gradually decreases with the increase of imbibition distance. Permeability and pore size affect the sweep of water in the process of huff and puff and the second migration of crude oil in large and small pore channels,therefore,it is necessary to expand the sweep range of injected water as much as possible in the development practices. At the same time,it is also important to pay attention to the secondary migration of oil and water in the pores with different sizes.