Study on Improving Recovery of Condensate Oil in Low Perm and High Condensate Gas Reservoir

Abstract

A low permeable sand conglomerate condensate gas reservoir in Bohai Sea has a high content of condensate oil and a small pressure difference between the ground and the dew point. When it is put into operation, the formation will be blocked by retrograde condensate, resulting in the loss of condensate oil. In order to find out the specific measures to improve the recovery of condensate, the effect of injection timing and volume on oil displacement efficiency was analyzed by long core cyclic gas injection experiment, and then the timing and volume of gas injection were optimized by numerical simulation. The long core cyclic gas injection experiment shows that the oil displacement efficiency of gas injection under the original formation pressure is much higher than that of gas injection under the condition of depletion to the maximum reverse condensate pressure; the oil displacement efficiency of gas injection under the original formation pressure increases with the increase of injection volume, but the increase of oil displacement efficiency decreases after gas channeling. The optimization results of numerical simulation also show that: for this kind of high condensate gas reservoir with near dew point pressure, initial gas injection and increasing injection volume are beneficial to improve the recovery ratio of condensate oil; compared with the recovery ratio of 16% for exhausted development of condensate oil, the recovery ratio of condensate oil for 100% reinjection can reach 32.78%. Through the long core cyclic gas injection experiment and numerical simulation optimization, the optimal gas injection strategy will be directly used to improve the recovery of condensate in this condensate gas reservoir.KeywordsLow permeabilityHigh condensate gas reservoirRecovery ratio