| Summary: | 博士 === 國立臺灣大學 === 地質科學研究所 === 102 === A safe geological space with enough storage capacity is vital to the carbon geo-sequestration development program. Intensive studies for 1.building-up a realistic basin-scale 3-D geological model, 2.assessing the effective and practical carbon dioxide storage capacity in the underground saline aquifer, 3.the numerical modeling for simulating CO2 injecting safety within the aquifer are deemed necessary and become the three main objectives of this thesis study.
Using Taihsi Basin in the western Taiwan as a example, the safety criterion for CO2 geological storage in saline aquifers is set for target geo-sequestration groups with four threshold condition including: 1.Safe top/bottom (900 m/3,000 m) depth of storage reservoirs, 2.Safe thickness (40 m) of cap rock, 3.Excluding area with unsafe distance (<5 km) from on-shore active faults, 4.Excluding underlying pre-existing faults cutting through cap rock. Within Taihsi Basin, the areal extent of the Area of Interest (AOI) and total volume of storage capacity had been further revised towards two selected sequestration groups (e.g. Chinshui Fm./Kueichulin Fm. Group and Talu Fm./Peiliao Fm. Group) in which the safe and effective carbon sequestration can be ensured.
Effective carbon dioxide storage capacity in the underground aquifers is estimated by volumetric estimating method respectively for two selected Sequestration Groups. Moreover, Effective volume of the deep saline aquifers has been estimated using the GIS graphic skill to allocate the safe areal extent of the cap rock and delineate the safe thickness of storage (reservoir) rock stratum. Generation of 3-D geological Model has been made possible by collecting the isopatch (depth contour) maps for all relevant target Formations surrounding and underlying the study area.
The CO2 storage capacity for each selected sequestration Group in the 3-D model can be calculated by giving all the parametric values required in the empirical formula involved in a volumetric estimating method. In this study, this effective storage capacity calculated for Chinshui Fm./Kueichulin Fm. Group is around 8.7×109 tons (8.7 Giga-tons), while the effective storage capacity for Talu Fm./Peiliao Fm. Group is around 3.8×109 tons (3.8 Giga-tons).
Relevant permeability vs. saturation (K-S) curves for porous sandstone cores sampled from a candidate reservoir rocks had been obtained in the Takeng area of Taichung. The K-S curves are regarded as critical input parameters controlling the feasibility of geo-sequestration in a deep saline aquifer. A two-phase flow or core-flooding test process using the displacement method with constant flow injection has been successfully established with corresponding tests successfully carried out. It has been also shown that K-S curves obtained directly from the test results in the drainage cycle can provide essential inputs for numerical simulation study. To enhance their reliability and real-world applicability, the input parameters should be calibrated by history match processes using computer code, e.g. TOUGH2.
It has been noted that effective and practical storage capacity can be recognized in a well defined 3-D geological model contained aquifers (reservoirs) with relevant CO2 injectivity. Key issues regarding the optimally utilization of safe reservoir space are investigated, including 1.Study of the optimal number of injection wells, 2.Study of total injectable amount under a multi-well configuration, and 3.Study of pressure build up within the injected aquifer.
Numerical modeling regarding safety scenarios for carbon geo-sequestration within the Taihsi Basin had been conducted by PetraSim simulator. The modeling can provide not only crucial information regarding the simulated plume migration path, but also the scenarios analysis to design sophisticated plan for engineering feasibility study. Most of the key input parameters used in the simulation is borrowed from some empirical data including pre-existing rock core investigation data and well logging results from local oil and gas exploration by CPC Corporation, Taiwan adjacent to the Taihsi Basin.
|
|---|
