致密油藏大模型逆向渗吸的物理模拟实验研究

Physical Simulation Experiment Investigation on Large Scale Model Using Countercurrent Imbibition in Tight Oil Reservoirs

为了研究致密油藏压裂和注水吞吐过程中逆向渗吸采油机理,通过大型露头岩样物理模拟实验系统,建立致密油藏逆向渗吸物理模拟实验系统和反向驱替渗流阻力测量物理模拟实验方法,对两种不同渗透率模型进行逆向渗吸物理模拟实验,研究逆向渗吸渗过程中的渗流规律,揭示逆向渗吸采油机理。研究结果表明:在实验条件下,逆向渗吸采油效果很弱,且渗透率越低,逆向渗吸置换效果越差;水通过毛管力进入基质置换其中的油,并在裂缝附近区域形成油水混合带,阻碍流体流动;2 m D和0.2 m D露头模型逆向渗吸作用区域分别为10 cm和8 cm;在逆向渗吸作用区域内,2 m D和0.2 m D露头模型逆向渗吸采出程度分别为6.3%和3.7%。

For investigating the recovery mechanism of countercurrent imbibition in the process of hydraulic fracturing and shut in well in cyclic water injection,experiment system of countercurrent imbibition in tight oil reservoir and experiment method of back-flooding percolation resistance measurement were established by high-pressure physical simulation system for large scale outcrops.Two different permeability models were employed in the physical simulation of countercurrent imbibition,and the corresponding flow mechanism were analyzed.The results show that under the experimental conditions,the effect of countercurrent imbibition is very bad,and the lower of the permeability is,the worse the effect of countercurrent imbibition is.Water enters the matrix through the capillary force to replace the oil,and forms an oil-water mixing zone in the zone of the fracture which hinders fluid flow.The countercurrent imbibition swept distances of the 2 mD and 0.2 mD outcrop model are 10 cm and 8 cm,in this area,recovery percent of the 2 mD and 0.2 mD outcrop model are 6.3%and 3.7%.