| dc.description.abstract | At present, the most effective method to store carbon dioxide (CO2) in geological sequestration is to inject of CO2 directly into saline aquifer or abandoned oil-gas fields. The shallow zones of Tiehchanshan’s (TCS) structure in the TCS gas field, recognized as a region without oil-gas productivity, has not been studied in the past, but holds promising for CO2 sequestration. . In order to accurately estimate the CO2 storage capacity of shallow structure trap, this study collected well, seismic and logging data in the TCS gas field, then followed the standard operating procedure of seismic interpretation to draw structural maps of target formations and the distribution of faults. Monte Carlo simulations was used to estimate CO2 storage capacity in the shallow zones of TCS structure, which include the Sangfuchi Sandstone, Kueichulin Formation, Chinshui Shale and the lower part of Cholan Formation sequence in the shallow zone.
The TCS structure is composed of two anticlines, including the Tonsiao anticline and the Tiehchanshan anticline, both verging towards the West and accompanied by normal faults. Isopatch maps of the Kuelchulin Formation and lower part of the Cholan Formation show that stratigraphic thickness is thinner along the anticlinal axis than in other regions of the TCS structure, as showing in wells of T-20, 16, 17 and 21. It can be deduced that the paleo topographic high during the period of sedimentation corresponds to the present anticlinal axis. The late reverse faulting resulted in the eastward migration of the anticlinal axis from surface toward depth.
The height of structural closure of the Kueichulin Formation is about -1980 m, this coupled with high porosity and permeability makes the Kueichulin Formation a good reservoir for CO2 sequestration. The relatively impermeable Chinshui and Shihliufen Shale can function as cap rocks. In addition, the overlying Cholan Formation can also act as additional seal that would potentially increase the security of CO2 sequestration. Based upon Monte Carlo simulation, the CO2 storage capacity in TCS gas field is about 356 billion m3 (0.64 billion tons). Moreover, the TCS structure is located in the tableland of Western Coastal Plain, in a relatively undeveloped area and near the main source of CO2 emission in Taiwan; thus the TCS structure is considered as one of the best sites for CO2 geologic sequestration.
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