CO2 Utilization Ratio Simulation during a CO2 Huff-and-Puff Process in Ultra-Low Permeability Oil Reservoirs

Abstract

CO2 huff-and-puff is an effective method in the development of extra-low permeability and ultra-low permeability reservoirs. In order to use this technique to cut the cost and increase oil recovery in oilfields, the gas utilization ratio during CO2 huff-and-puff process was investigated. CO2 huff-and-puff tests using ultra-low permeability cores from Changqing Oilfield were carried out to investigate oil recovery factors and CO2 utilization under different injection pressures. The test results show that ultimate oil recovery increases with the increase of injection pressure and the increasing amplitude would decrease gradually. In addition, CO2 utilization ratio is relatively high in the first four cycles, but is significantly reduced with the increase of huff-and-puff cycles. The increasing of injection pressure can make the CO2-crude oil system enter into a miscible phase condition, which is beneficial for obtaining higher oil recovery without significant increase of the cost of CO2 supply. The results show that CO2 huff-and-puff with four cycles will be close to miscible condition and could achieve better development effect and economic benefits.

AAPG Datapages/Search and Discovery Article #130005© Petroleum Drilling Techniques, Issue 6, 2018