直流电提高低渗透砂岩油藏驱油效率实验

Laboratory investigation on enhanced displacement efficiency of oil sandstone reservoirs with low permeability by direct current

针对我国渗透油藏敏感性矿物丰富、孔隙喉道小、微孔隙发育、比表面积大、流体与岩石界面作用力显著等特点,利用水驱油实验研究了反向直流电场对岩样水驱油效率的影响。结果表明:不同渗透率岩样具有对应的最佳直流电电位梯度,低于该电位梯度,驱油效率随电位梯度的增加而增加,高于此电位梯度,反而出现驱油效率下降的现象。依岩样物性的不同,在直流电场的电化学、电泳及电渗效应等作用下可以提高室内水驱油效率3.20%～11.94%不等,当岩样渗透率位于20×10-3um2左右时,电场提高的驱油效率值达到最大,渗透率继续增加,所提高的驱油效率反而开始下降,证实了利用反向直流电提高水驱油效率,特别是低渗透油层水驱油效率的有效性。同时,直流电具有阻滞水流,相应增加油相流动能力的效应,从而能有效降低油井含水率。

Low radius of pore and throat,high content of clay mineral,microporosity developing,high specific surface area and the interface action between rock and its contact fluid is strong,which are features of oil sandstone reservoirs with low permeability.The oil recovery technique of direct current is a new efficient development technology to address these problems,aimed to increase oil production and recovery.The article studied the effect of reverse DC on rock samples.The results showed that: The rock with different permeability has the best potential gradient of reverse DC.If the potential gradient lower than the best gradient,displacement efficiency will increase with the increasing potential gradient,but,if higher than the best,the displacement efficiency will decline.According to the physical property of different rock,the reverse DC technique raises the indoor water displacement efficiency by 3.20%~11.94% under the effects of electrochemistry,electrophoresis and electroosmosis,and so on.And the enhanced displacement efficiency reaches the maximize value when the permeability is about 20×10-3μm2.With the permeability continue to increase,the enhanced value of displacement efficiency begins to decline,all of which shows the validity of using reverse DC to improve the efficiency of water flooding,especially for the low permeability reservoirs.At the same time,the DC can block the water flow,thus correspondingly increase the capacity of oil flow,and ultimately can reduce the water content of oil well.