Technologies and practice of CO₂ flooding and sequestration in China

HU Yongle,HAO Mingqiang,CHEN Guoli,SUN Ruiyan,LI Shi

Table 4 Evaluation indexes and connotations for safe CO₂ sequestration.

Evaluation objects	Indexes	Connotations
Basins	Tectonic feature	The structure must be stable with few earthquake activities, for example, foreland basin and inner craton basin.
	Hydrodynamic condition	The hydrodynamic system should have large burial depth and certain regional scale, and be controlled by the topographic and geomorphological fluctuations.
	Geothermal feature	Cold basins are more conducive to high density CO₂ sequestration than hot basins, which can increase the sequestration capacity.
	Exploration degree	Basins with high exploration degree and detailed information of development wells can provide reliable data for monitoring CO₂ leakage.
Geological bodies	Tectonic condition	Without fault or fracture, and the slope zone is the favorable zone.
	Caprock condition	In order to ensure long-term CO₂ sequestration, the caprock thickness and integrity are very important.
	Scale condition	Should be regional scale.
	Burial condition	Burial depth should be large enough to ensure the critical or supercritical state of buried CO₂, while ensuring the safety of freshwater resources.
	Poroperm condition	High porosity and high permeability are needed to ensure CO₂ injection and sequestration.
	Fluid properties	Dissolved sequestration and mineralization reaction are important forms of underground CO₂ sequestration. The salinity condition of formation water should be considered.
	Matrix mineral	Chemical reaction between CO₂ and matrix minerals under reservoir conditions generating new stable minerals is an important form of safe CO₂ sequestration. The sequestration amount is dependent on matrix mineral composition.