Carbon dioxide enhanced oil recovery (CO2-EOR) and sequestration in depleted oil reservoirs is a plausible option for utilizing anthropogenic CO2 to increase oil production while storing CO2 underground. Evaluation of the storage resources and cost of potential CO2-EOR projects is an essential step before the commencement of large-scale deployment of such activities. In this paper, a hybrid techno-economic evaluation method, including a performance model and cost model for onshore CO2-EOR projects, has been developed based on previous studies. Total 296 onshore oil fields, accounting for about 70% of total mature onshore oil fields in China, were evaluated by the techno-economic method. The key findings of this study are summarized as follows: (1) deterministic analysis shows there are approximately 1.1 billion tons (7.7 billion barrels) of incremental crude oil and 2.2 billion tons CO2 storage resource for onshore CO2-EOR at net positive revenue within the Chinese oil fields reviewed under the given operating strategy and economic assumptions. (2) Sensitivity study highlights that the cumulative oil production and cumulative CO2 storage resource are very sensitive to crude oil price, CO2 cost, project lifetime, discount rate and tax policy. High oil price, short project lifetime, low discount rate, low CO2 cost, and low tax policy can greatly increase the net income of the oil enterprise, incremental oil recovery and CO2 storage resource. (3) From this techno-economic evaluation, the major barriers to large-scale deployment of CO2-EOR include complex geological conditions, low API of crude oil, high tax policy, and lack of incentives for the CO2-EOR project

Carbon dioxide (CO2) capture and storage (CCS) is considered widely as one of promising options for CO2 emissions reduction, especially for those countries with coal-dominant energy mix like China. Injecting and storing a huge volume of CO2 in deep formations are likely to cause a series of geomechanical issues, including ground surface uplift, damage of caprock integrity, and fault reactivation. The Shenhua CCS demonstration project in Ordos Basin, China, is the first and the largest full-chain saline aquifer storage project of CO2 in Asia. The injection started in 2010 and ended in 2015, during which totally 0.3 million tonnes (Mt) CO2 was injected. The project is unique in which CO2 was injected into 18 sandstone formations simultaneously and the overlying coal seams will be mined after the injection stopped in 2015. Hence, intense geomechanical studies and monitoring works have been conducted in recent years, including possible damage resulting from the temperature difference between injected CO2 and formations, injection induced stress and deformation change, potential failure mode and safety factor, interaction between coal mining and CO2 geological storage, determination of injection pressure limit, and surface monitoring by the interferometric synthetic aperture radar (InSAR) technology. In this paper, we first described the background and its geological conditions of the Shenhua CCS demonstration project. Then, we gave an introduction to the coupled thermo-hydro-mechano-chemical (THMC) processes in CO2 geological storage, and mapped the key geomechanical issues into the THMC processes accordingly. Next, we proposed a generalized geomechanical research flowchart for CO2 geological storage projects. After that, we addressed and discussed some typical geomechanical issues, including design of injection pressure limit, CO2 injection induced near-field damage, and interaction between CO2 geological storage and coal mining, in the Shenhua CCS demonstration project. Finally, we concluded some insights to this CCS project.

The Liujiagou formation is an important CO₂ aquifer storage unit in the Ordos Basin in central China. Thus far, it has stored over 90% of the total injected CO₂ from the Shenhua carbon capture and storage (CCS) project, which is the first full‐chain CCS project in China. Understanding the basic properties of CO₂ flooding is critical for site characterization and evaluation. A core‐scale characterization and CO₂ flooding study of Liujiagou sandstone is the first step to understanding the flooding properties in a CO₂ aquifer storage project. The pore geometry of a sample was characterized using medical, industrial, and micro X‐ray computed tomography (X‐CT) scanners, as well as mercury intrusion porosity and thin section petrography. To study the flooding process, a CO₂ core flooding experiment using medical X‐CT scanning was conducted with a Liujiagou sandstone sample. Based on the CT data, experimental data, simplified models and COMSOL software, a three‐dimensional sub‐core scale numerical model that considered porosity, permeability, and capillary pressure heterogeneity was constructed for numerical simulation of CO₂ flooding under different scenarios. Laboratory experiments and numerical simulations on a Liujiagou sample revealed the following. The Liujiagou sandstone is a low‐porosity and low‐permeability sandstone with very high heterogeneity. The sub‐core porosity heterogeneity significantly affects CO₂ migration. The relative permeability and saturation distribution are significantly affected by the injection velocity of CO₂ and are different from those of other sandstones, such as Berea. The analyzed Liujiagou sandstone sample has a very low storage efficiency factor at the core scale.