致密油藏活性水采油机理

注活性水相较于注水有诸多优势,在特低渗、超低渗油藏的实际开发中效果较好,因此可以借鉴到致密油藏的开发上。针对鄂尔多斯盆地X区块致密油储层,选取不同渗透率的岩心进行注水和注活性水驱油物理模拟实验,结合核磁共振技术,分析致密油岩心的微观孔隙结构、可动流体饱和度以及不同渗透率等级岩心的采出程度、残余油分布等。研究表明:大部分致密油油藏的孔隙为亚微米、微纳米孔,可动流体主要赋存于大于1μm的孔隙中;注活性水效果好于常规水驱,注活性水能够有效地动用微纳米孔中的原油;渗透率越低注活性水的驱油效果越明显,对于渗透率低于0.6×10~(-3)μm的致密油藏,建议采用注活性水开发。

OIL DISPLACING MECHANISM FOR THE ACTIVE WATER FLOODING IN TIGHT OIL RESERVOIRS

Compared with water flooding,active water flooding has many advantages,and moreover it can achievemuch better effects in the development of extra-low and ultra-low permeability oil reservoirs,therefore it can be used for the reference to the development of tight oil reservoirs.In the light of Block X tight oil reservoirs in Ordos Basin,different permeability cores are selected to conductoil-displacing physical simulating experiment by water and active water floodings,and furthermore integrating nuclear magnetic resonance (NMR) technique,themicro-hole structure,movable fluid mobility,recovery degree of different-grade permeability cores,residual oil distribution and so on were analyzed for the tight oil.The researches show that most of the pores are sub-micro and micro-nano ones,the movable fluid is mainly stored in the pores of more than 1 μm,the effects of active water flooding are much better than those of conventional water flooding,for it can effectively develop the oil in the micro-nano holes;the lower the permeability is,the more obvious effects will be;for the tight oil reservoir with permeability less than 0.6×10-3 μm2,the active water flooding is recommended.