Immiscible CO2-Assisted Gravity Drainage Process for Enhancing Oil Recovery in Bottom Water Drive reservoir

Abstract

The CO2-Assisted Gravity Drainage process (GAGD) has been introduced to become one of the most
influential process to enhance oil recovery (EOR) methods in both secondary and tertiary recovery through immiscible
and miscible mode. Its advantages came from the ability of this process to provide gravity-stable oil displacement for
enhancing oil recovery. Vertical injectors for CO2 gas have been placed at the crest of the pay zone to form a gas cap
which drain the oil towards the horizontal producing oil wells located above the oil-water-contact. The advantage of
horizontal well is to provide big drainage area and small pressure drawdown due to the long penetration. Many
simulation and physical models of CO2-AGD process have been implemented at reservoir and ambient conditions to
study the effect of this method to improve oil recovery and to examine the most parameters that control the CO2-AGD
process. The CO2-AGD process has been developed and tested to increase oil recovery in reservoirs with bottom water
drive and strong water coning tendencies. In this study, a scaled prototype 3D simulation model with bottom water
drive was used for CO2-assisted gravity drainage. The CO2-AGD process performance was studied. Also the effects of
bottom water drive on the performance of immiscible CO2 assisted gravity drainage (enhanced oil recovery and water
cut) was investigated. Four different statements scenarios through CO2-AGD process were implemented. Results
revealed that: ultimate oil recovery factor increases considerably when implemented CO2-AGD process (from 13.5%
to 84.3%). Recovery factor rises with increasing the activity of bottom water drive (from 77.5% to 84.3%). Also,
GAGD process provides better reservoir pressure maintenance to keep water cut near 0% limit until gas flood front
reaches the production well if the aquifer is active, and stays near 0% limit at all prediction period for limited water
drive.