The Enhanced Oil Recovery Effect of Nitrogen-Assisted Gravity Drainage in Karst Reservoirs with Different Genesis: A Case Study of the Tahe Oilfield

For the Tahe Oilfield, there are multiple sets of karst reservoirs with different genesis developed in carbonate fracture-vuggy and varying reservoir type has a considerable influence on distribution residual oil. The complex characteristics difficulty producing remaining oil middle lower part greatly restrict recovery effects. This work managed to comprehensively investigate action mechanism nitrogen-assisted gravity drainage (NAGD) through modeling experiments. Based geological results, reservoir-profile model considering type, fracture distribution, fracture–cave combination was established, displacement experiments main such as epikarst zone, underground river, fault were carried out, oil–gas–water multiphase flow visually analyzed. state before after NAGD studied, difference enhancement genetic quantitatively compared. results show that helpful enhancing (EOR) for genesis. technique greatest increasing effect sweep efficiency fault-karst reservoir, followed by zone smallest river reservoir. this research will facilitate an understanding EOR karst-reservoir types provide theory technical support high-efficiency development Oilfield.