表面活性剂对特低渗岩心启动压力梯度的影响

INFLUENCES OF THE SURFACTANT ON THE STARTING PRESSURE GRADIENT OF THE EXTRA-LOW-PERMEABILITY CORE

特低渗油藏微观孔隙结构复杂,启动压力梯度对流体的渗流规律影响很大。针对胜利油田史深100区块特低渗岩心,通过驱替实验分别研究表面活性剂对岩心单相流体以及油水两相启动压力梯度的影响。结果表明:不论地层水条件还是表面活性剂条件下,特低渗岩心都存在启动压力梯度,注入表面活性剂后岩心的最小启动压力梯度与拟启动压力梯度明显降低,且表面活性剂质量浓度越高,对启动压力和非达西渗流影响越大;特低渗岩心中油水两相流动时随油水驱替速率比的降低,两相启动压力梯度逐渐降低,含水饱和度逐渐升高,相同的油水速率比下,随油水界面张力的降低,两相启动压力梯度逐渐降低,含水饱和度逐渐增大,且随着表面活性剂溶液比例的增大,对两相启动压力梯度和含水饱和度的影响增加。

The micro-pore structures of the extra-low-permeability reservoir are rather complex, the influences of the starting pressure gradient on the seepage laws of the fluids are serious. Aiming at the extra-low-permeability cores form Block Shishen-lO0 in Shengli Oilfield, the influences of the surfactant on the starting pressure gradients of single phase fluid and oil-water two phases are studied respectively by means of the flooding experiments. The re- sults show that whether under the condition of the water flooding or surfaetant flooding, there is the starting pressure gradient for the extra-low-permeability cores, after the surfaetant flooding, the minimum and pseudo starting pres- sure gradients are decreased significantly, the higher the surfactant mass concentration is, the greater the influences on the starting pressure non-Darcy flow will be ; for the extra-low-permeability cores, with the drop of the oil-water displacing velocity ratio, the starting pressure gradients of the two phases are gradually decreased, and water satura- tion gradually increased, as the ratio of displacing velocity of oil-water two-phase decreased, while the water satura- lion is gradually increased, at the same ratio, with the reduction of the oil-water inteffacial tension, the starting pressure gradients of the oil-water two phase are gradually decreased, on the contrary , the water saturation is risen step by step, and furthermore with the rise of the snffactant solution proportion, the influences on the two-phase starling pressure gradients and water saturation are increased as well.