致密油储层注水吞吐动态渗吸特征及影响因素

Dynamic Imbibition Characteristics and Influencing Factors of Water Injection Huff-puff in Tight Oil Reservoir

为明确致密油藏注水吞吐渗吸驱油机理,评价各因素对渗吸驱油效果的影响,以鄂尔多斯盆地西北部地区长7储层天然岩心为研究对象,开展了岩心注水吞吐渗吸驱油实验,评价了表面活性剂类型、原油黏度、渗透率、润湿性、裂缝发育程度、体面比和生产压差对吞吐渗吸开发的影响。结果表明:HYS-3非离子表面活性剂提高渗吸效果最为明显,而DTAB效果最差,表面活性剂能够有效降低油水界面张力,改变岩石表面润湿性,减小油水渗流阻力,增加孔隙吸水能力,扩大波及面积。吞吐渗吸采出程度随原油黏度和体面比的增加而减小,随渗透率、亲水程度和裂缝发育程度的增加而增大;而增大生产压差仅能加快渗吸速率,对渗吸驱油效率影响较小。矿场试验结果表明,试验井组经过3轮吞吐渗吸后,日均产油量增幅达235%,日均含水率下降幅度达28.4%,增油降水效果显著。

The water injection huff-puff imbibition oil displacement experiments of the natural cores from Chang 7 reservoir in northwestern Ordos Basin were carried out,and the effects of surfactant type,crude oil viscosity,core permeability,wettability,fracture development degree,volume-to-surface area ratio and production pressure difference on the water injection huff-puff imbibition oil displacement effect were evaluated.The results show that the imbibition improving effect of HYS-3 nonionic surfactant is the most obvious,while that of DTAB is the worst.The surfactant can effectively reduce the oil-water interfacial tension,change the rock surface wettability,reduce the oil-water seepage resistance,increase the pore water absorption capacity and expand the swept area.The producing degree of water injection huff-puff imbibition decreases with the increase of crude oil viscosity and volume-to-surface area ratio,and increases with the increase of core permeability,hydrophilic degree and fracture development degree;increasing production pressure difference can only accelerate the imbibition rate,but has little effect on the imbibition displacement efficiency.The field test results show that after three cycles of huff and puff,the average daily oil production of the test wells increases by 235%,and the average daily water cut decreases by 28.4%.The water injection huff-puff imbibition oil displacement has obvious oil production increasing and water cut reducing effect.