Optimization of well placement and operating conditions for various well patterns in CO2 sequestration in the Pohang Basin, Korea

Abstract

The aquifer consists of multi-layers and has pre-existing faults and heterogeneous reservoir properties that restrict CO2 injection to a certain amount. To store large amounts of CO2 and maintain storage security, it is important to define the optimal injection well pattern, placement, and operating conditions. This study applied various well patterns and optimized their locations and fluid injection rates with monitoring the pressure build-up in the aquifer to improve the storage capacity. Four well patterns in this study were employed: (1) a single vertical injection well (SVI), (2) two vertical injection wells (TVI), (3) a single horizontal injection well (SHI), and (4) two vertical wells for brine extraction and CO2 injection (TVEI). The results showed TVEI at the optimal location and fluid rate that allowed an almost eight times larger volume of CO2 to be stored compared to the base case (simulation result of SVI drilled for the CO2 storage pilot project in the Pohang basin, Korea), and maintained the pressure within the boundary for security. When using a single well (SVI and SHI), SVI injected 126 kton of CO2, which is larger than that of SHI, but storage security of SHI is better than that of SVI due to the difference in CO2 migration. Through this research, the effects of various well patterns in CO2 geological storage in the Pohang Basin can be forecasted and the optimal well pattern and conditions for the largest storage capacity can be determined.