Frozen core experimental study on oil-water distribution characteristics at different stages of water flooding in low permeability oil reservoirs

The distribution pattern of oil and water in different stages of low permeability reservoirs is one of the main research topics in oilfield development. This paper takes low-permeability and tight oil reservoirs as the research object, systematically carries out experimental research on water flooding efficiency, and carries out theoretical comparative analysis. The innovations of this paper mainly include three aspect: (a) the experimental study of water drive efficiency under the conditions of different water drive stages is carried out, and the dynamic evolution characteristics of remaining oil distribution is analyzed. (b) The comparative analysis of water drive efficiency under different combination conditions of “permeability and crude oil physical properties” is studied. (c) The dynamic evolution mechanism of the coupling of “bound water - semi-bound water - free water” is explored by using the frozen core method. Results show that: (a) At the original oil bearing stage of the core in F Oilfield, the free microscale residual oil is the majority, followed by the bound and semi-bound residual oil. (b) Water flooding mainly develops the free residual oil. The remaining oil in clusters decreased from 22.35% to 2.21%. The residual oil in the form of inter-particle adsorption decreased from 28.56% to 2.53%. (c) It is difficult to develop bound and semi-bound residual oil in water drive. As the cluster like remaining oil is developed, the facial mask like remaining oil on the pore surface increases from 1.13% to 4.04%.