Dynamic and static imbibition characteristics of tight sandstone based on NMR

Abstract

The study of the imbibition characteristics is significant as the main means of tight sandstone reservoir development. Static imbibition and dynamic imbibition displacement experiments were carried out with the cores of the Yanchang formation in the Ordos Basin. We studied the effects of the permeability on the imbibition recovery and analyzed the forces of the static imbibition and dynamic imbibition displacement. Finally, combined with the nuclear magnetic resonance technique, the fluid distributions in the core pores and the changes in the fluid signals in the processes of dynamic and static imbibition were analyzed, and the effects of pores of different scales on the static imbibition and displacement recovery were explored. The results showed that the static imbibition and dynamic imbibition displacement recovery increased with the increase in the permeability. Finally, using nuclear magnetic resonance analysis, it was found that dynamic imbibition displacement is an imbibition process driven mainly by the displacement pressure, and its recovery, about 24.20%, is mainly determined by macropores. Static imbibition is an imbibition process driven mainly by capillary forces. The recovery, about 31.15%, is also determined by macropores, but the effects of mesopores and micropores cannot be ignored. In addition, through the comparative analysis of different pores, it was found that the effects of the displacement pressure and capillary forces in different pores were different. Therefore, the displacement pressure of dynamic imbibition and the capillary forces of static imbibition should be reasonably used to improve the recovery degree of tight reservoirs.