驱替过程中重力舌进特征的核磁共振可视化实验

Nuclear magnetic resonance visualization experiment of gravity tongue characteristics in the displacement process

重力舌进是一种岩心驱替实验中常见的由于重力作用导致驱替剂沿岩心上缘或下缘突进的现象,其直接影响驱替剂的应用效果。由于在驱替过程中无法对岩心内部进行直接观察,因此对重力舌进现象没有直观的认识。利用油藏数值模拟方法模拟了重力对水驱油过程中流体流动形态的影响,并利用基于核磁共振成像技术的岩心驱替可视化实验方法研究了重力舌进产生的条件及影响因素,同时提出了一种获得产生重力舌进特征临界密度差的新方法。研究结果表明,驱替流体与被驱替流体的密度差是产生重力舌进现象最直接的原因;当实际的密度差大于临界密度差时,则产生显著的重力舌进现象;驱替介质的黏度和驱替流量对重力舌进特征的影响并不明显;在实际生产过程中,可以根据地层流体性质优选驱替液的密度,减少重力舌进对驱替效果的影响。

Gravity tonguing is a common phenomenon that the displacement agent flows forward rapidly along the upper or lower core edge due to gravity action in the core displacement experiment,which directly affects the effect of displacement agent.For a long term,it is unable to directly observe the core interior in the displacement process,so it is impossible to form an intuitive image of that phenomenon.Firstly,the influence of gravity on fluid flow morphology in the process of water flooding was simulated by means of reservoir numerical simulation.Then,the conditions and influencing factors of gravity tonguing were studied using the core displacement visualization method based on magnetic resonance imaging technique.A new method was proposed to obtain the critical density difference causing gravity tonguing.Research results show that the density difference of displacement fluid and displaced fluid is the most direct reason for gravity tonguing.When the actual density difference is greater than the critical value,significant gravity tonguing will occur.The viscosity and displacement flow of displacement medium have no obvious influence on gravity tonguing.In the actual production process,the density of displacement fluid can be selected preferentially based on formation fluid property to reduce the influence of gravity tonguing on displacement effect.