渤海湾盆地永安油田永66区块氮气驱油机理

Mechanism of nitrogen flooding in Yong 66 block of Yong’an Oilfield,Bohai Bay Basin

为研究渤海湾盆地永安油田永66区块氮气驱油机理及其变化规律,在地质认识基础上开展了流体相态实验和数值模拟研究。结果表明:①注氮气吞吐过程中,地层倾角、驱替速度以及毛管压力的大小对地层含油饱和度和界面张力的变化均具有明显控制作用;②地层倾角越大、驱替速度越快,原油越容易被驱替至油藏底部,从而油藏底部的含油饱和度越大,而油藏顶部流体则变成油气两相,界面张力增加;③在氮气驱油过程中,随着毛管压力的增加,气体进入孔隙的阻力增大,底部含油饱和度也会随之增大,但原油向油层底部聚集的速度减慢,顶部界面张力增大,含油饱和度和界面张力变化的范围和程度逐渐减小。该研究成果对油气田开发过程中利用氮气驱油提高采收率具有指导作用。

In order to study the mechanism of nitrogen flooding and its variation law in Yong 66 block of Yong’an Oilfield in Bohai Bay Basin,fluid phase experiments and numerical simulations were carried out on the basis of geological study.The results show that:(1)During the nitrogen injection process,the formation dip angle,displacement velocity and capillary pressure have obvious effects on the change of oil saturation and interfacial tension.(2)The greater the formation dip angle and displacement velocity are,more crude oil is displaced to the bottom of the reservoir,the greater the oil saturation at the bottom of the reservoir is.At the same time,the upper fluid of the reservoir becomes the two phases of oil and gas,and the interfacial tension increases.(3)During the process of nitrogen flooding,as the capillary pressure increases,the resistance of the gas entering into the pores increases,and so does the oil saturation at the bottom,although the accumulation of crude oil to the bottom of the reservoir slows down.Also,the tension at the top interface increases,while the range and degree of the change gradually decreases.The research results have a guiding role in the application of nitrogen flooding to enhance oil recovery in the development of oil and gas fields.