Evaluating the climate benefits of CO2-enhanced oil recovery using life cycle analysis

Life cycle assessment of alternative biogas utilisations, including carbon capture and storage or utilisation

Biogas from anaerobic digestion is an important renewable energy source. Combining its utilisation with carbon capture and storage (CCS) or carbon capture and utilisation (CCU) may improve climate change performance. This study uses life cycle assessment to evaluate the environmental impacts of 17 biogas management technology configurations (TCs). The technologies include biogas combustion, upgrading to natural gas quality, CCS, direct utilisation of CO₂ and methanation. The focus is mainly on energy balances and climate change impacts, and the results are subjected to sensitivity-, uncertainty-, and energy system analysis. The TCs with CCS and CCU provide the largest climate change savings (-1400 to - 2100 kg CO₂-eq/1000 Nm³ biogas). Specifically, the methanation TCs provide the highest savings, but they also depend strongly on the energy sources. When combustion and upgrading TCs are amended with CCS, the resulting climate change savings are robust across the energy systems. The biogas upgrading TCs exhibit substantial climate change savings, mainly due to the natural gas substitution. Combustion TCs without CCS have the lowest climate change savings and the highest quantified uncertainties. The biogas upgrading TCs with storage or direct utilisation of CO₂ provide a good compromise between climate change savings and energy recovery. In the remaining impact categories, the CCU TCs generally perform best, followed by the upgrading TCs and finally, the combustion TCs. The CCS TCs consistently perform worse than their counterparts without CCS, opposite to the climate change results. Overall, amending biogas utilisation with CCS or CCU can contribute to climate change mitigation.

Techno-Economic Assessment and Life Cycle Assessment of CO2-EOR

CO₂-enhanced oil recovery (EOR) can have less GHG emissions compared to conventional oil production methods. The economy of CO₂-EOR can significantly benefit from the recent rise of carbon prices in carbon markets due to its greenhouse gas (GHG) emission savings. This study conducted a life cycle assessment (LCA) of CO₂-EOR in major hydrocarbon provinces of the world. Estimated net GHG emissions of CO₂-EOR were compared with GHG emissions of average produced oil in the given country. When sourcing CO₂ from coal-fired power plants, Kazakhstan and China have net GHG emissions of CO₂-EOR of 276 and 380 kg CO₂ eq/bbl, respectively, which are lower than the GHG emission factor of average oil produced in each of them. Significantly lower GHG emissions of CO₂-EOR are observed in other hydrocarbon provinces (Iraq, Saudi Arabia, Kuwait, etc.), where CO₂ could be delivered from Natural Gas Combined Cycle (NGCC) power plants. However, the cost of CO₂ capture is higher at NGCC power plants than at coal-fired power plants. Further, we developed a techno-economic assessment (TEA) model of the CO₂-EOR and integrated it with LCA to thoroughly consider carbon credits in its economy. The model was built based upon previous investigations and used statistics from a large industrial data set of CO₂-EOR to produce accurate estimates of the CO₂-EOR economy. The technical model iteratively estimated the balance of three fluids (crude oil, CO₂, and water) in the CO₂-EOR system with a 25 year operational lifespan and obtained actual data for the LCA and TEA models. The model was simulated for the Kazakhstan case with its oil market conditions for a demonstration purpose. TEA results showed that, with the available low-cost CO₂ capture source or high CO₂ cost in carbon trading, CO₂-EOR can compete with current upstream projects in Kazakhstan by simultaneously increasing oil production and reducing GHG emissions.

A Gate-to-Gate Life Cycle Assessment for the CO2-EOR Operations at Farnsworth Unit (FWU)

Greenhouse gas (GHG) emissions related to the Farnsworth Unit’s (FWU) carbon dioxide enhanced oil recovery (CO2-EOR) operations were accounted for through a gate-to-gate life cycle assessment (LCA) for a period of about 10 years, since start of injection to 2020, and predictions of 18 additional years of the CO2-EOR operation were made. The CO2 source for the FWU project has been 100% anthropogenically derived from the exhaust of an ethanol plant and a fertilizer plant. A cumulative amount of 5.25 × 106 tonnes of oil has been recovered through the injection of 1.64 × 106 tonnes of purchased CO2, of which 92% was stored during the 10-year period. An LCA analysis conducted on the various unit emissions of the FWU process yielded a net negative (positive storage) of 1.31 × 106 tonnes of CO2 equivalent, representing 79% of purchased CO2. An optimized 18-year forecasted analysis estimated 86% storage of the forecasted 3.21 × 106 tonnes of purchased CO2 with an equivalent 2.90 × 106 tonnes of crude oil produced by 2038. Major contributors to emissions were flaring/venting and energy usage for equipment. Improvements on the energy efficiency of equipment would reduce emissions further but this could be challenging. Improvement of injection capacity and elimination of venting/flaring or fugitive gas are methods more likely to be utilized for reducing net emissions and are the cases used for the optimized scenario in this work. This LCA illustrated the potential for the CO2-EOR operations in the FWU to store more CO2 with minimal emissions.

Significance of Enhanced Oil Recovery in Carbon Dioxide Emission Reduction

Limiting the increase in CO2 concentrations in the atmosphere, and at the same time, meeting the increased energy demand can be achieved by applying carbon capture, utilization and storage (CCUS) technologies, which hold potential as the bridge for energy and emission-intensive industries to decarbonization goals. At the moment, the only profitable industrial large-scale carbon sequestration projects are large-scale carbon dioxide enhanced oil recovery (CO2-EOR) projects. This paper gives a general overview of the indirect and direct use of captured CO2 in CCUS with a special focus on worldwide large-scale CO2-EOR projects and their lifecycle emissions. On the basis of scientific papers and technical reports, data from 23 contemporary large-scale CO2-EOR projects in different project stages were aggregated, pointing out all the specificities of the projects. The specificities of individual projects, along with the lack of standardized methodologies specific for estimating the full lifecycle emissions resulting from CO2-EOR projects, pose a challenge and contribute to uncertainties and wide flexibilities when estimating emissions from CO2-EOR projects, making the cross-referencing of CO2-EOR projects and its comparison to other climate-mitigation strategies rather difficult. Pointing out the mentioned project’s differentiations and aggregating data on the basis of an overview of large-scale CO2-EOR projects gives useful information for future work on the topic of a CO2-EOR project’s lifecycle emissions.

Ab Initio Molecular Dynamics Investigation of CH4/CO2 Adsorption on Calcite: Improving the Enhanced Gas Recovery Process

Ab initio molecular dynamics simulations of CH₄ and CO₂ on the calcite (104) surface have been carried out for the molecular level analysis of CO₂-enhanced gas recovery process (EGR). This process takes advantage of the stronger interaction of CO₂ with the reservoir walls compared to CH₄, therefore can improve the extraction of the latter, while at the same time sequestering the former underground. Pure and mixed gases were considered and the temperature effect on the systems behavior was analyzed. For pure gases, carbon dioxide shows great stability on the surface in the studied temperature range, while methane molecules start leaving the surface at 298 K. For gas mixtures, the reported results confirm that for low to medium concentrations, a temperature of 373 K could determine the best methane extraction efficiency, as CH₄ interaction with the surface is quite weak and carbon dioxide binds strongly on the surface. On the other hand, when full coverage is achieved, the best efficiency is reached for the highest temperature. Finally, when considered a 2:2 gas layer, carbon dioxide tends to adsorb preferentially to the surface while methane keeps floating above it, thereby reducing its chance to be adsorbed back. These results reveal nanoscopic details for the design of suitable EGR processes.

CO2-enhanced oil recovery and CO2 capture and storage: An environmental economic trade-off analysis

CO₂ enhanced oil recovery can play a significant role in stimulating carbon capture and storage because of additional oil revenues generated. However, it also leads to additional greenhouse gas emissions. We estimate the global warming potential of different CO₂ capture scenarios with and without enhanced oil recovery. During a 10 year period in which oil and electricity are produced without CO₂ being captured, the global warming potential is 11 MtCO₂ equivalents. We show that if CO₂ is captured and used for 15 years of enhanced oil recovery, the global warming potential decreases to 3.4 MtCO₂ equivalents. This level is 100% higher compared to the scenario in which the captured CO₂ would be stored in an offshore aquifer instead. If the capture of CO₂ is stopped when the oil reservoir is depleted, the global warming potential resulting from 10 years electricity production is 6 MtCO₂ equivalents. However, if CO₂ is stored in the depleted reservoir, the global warming potential is six times lower during that period. Electricity production and oil refining are the main contributors to the global warming potential. The net present value analysis indicates that for CO₂ prices lower than or equal to 15 €/t and oil prices greater than or equal to 115 €/t, it is most profitable to capture CO₂ for enhanced oil recovery only. Because of the low CO₂ price considered, large incomes from oil production are required to stimulate CO₂ capture. The environmental economic trade-off analysis shows that if CO₂-enhanced oil recovery is followed by CO₂ capture and storage, costs increase, but the net present value remains positive and the global warming potential is reduced. Authorities could use these outcomes to support the development of economic mechanisms for shared investments in CO₂ capture installations and to mandate both oil producer and large CO₂ emitting firms to store CO₂ in depleted oil fields.

Employment impact assessment of carbon capture and storage (CCS) in China's power sector based on input-output model

Carbon capture and storage (CCS) could be an effective measurement for carbon emission reduction in China. This paper summarizes the development of power sector in 2020, 2030, and 2050, and it classifies 18 scenarios including with and without CCS, respectively, in G1:low, G2:middle, and G3:high in 2020, 2030, and 2050. It adopts China's input-output table (IO table) and analyzes the different mitigation strategies for power sector. In particular, this paper builds a new China's input-output table based on aggregating the sectors in IO table and disaggregating the power sector into 11 different technologies which are coal-fire power, coal-fire power with CCS, natural gas power, natural gas power with CCS, hydropower, nuclear power, wind power, solar power, biomass power, geothermal power, and ocean power. Through input-output model, this paper estimates gross value added (GVA) and employment effects of different scenarios of different technologies in power sector in China. It finds that the differences of GVA and employment effects among different scenarios are large. In CCS scenarios, the coal-fire power with CCS contribute 1.48-1.63 × 10¹⁰ RMB in 2020, 1.09-1.55 × 10¹⁰ RMB in 2030, and 0.85-1.20 × 10¹⁰ RMB in 2050 for gross value added. Meanwhile, the employments of coal-fire power with CCS can add the jobs of 11,966-17,159 in 2020; 10,419-16,228 in 2030; and 8977-12,571 in 2050. CCS sector contributes the higher employment than in the renewable power sectors. Meanwhile, coal mining industry, equipment manufacturing industry, and metallic industry take main contribution to the employment of CCS sector.

Expansion of the Petroleum Refinery Life Cycle Inventory Model to Support Characterization of a Full Suite of Commonly Tracked Impact Potentials

This study updates the Petroleum Refinery Life Cycle Inventory Model (PRELIM) to provide a more complete gate-to-gate life cycle inventory and to allow for the calculation of a full suite of impact potentials commonly used in life cycle assessment (LCA) studies. Prior to this update, PRELIM provided results for energy use and greenhouse gas emissions from petroleum refineries with a level of detail suitable for most LCA studies in support of policy decisions. We updated the model to add criteria air pollutants, hazardous air pollutants, releases to water, releases to land, and managed wastes reflecting 2014 reported releases and waste management practices using data from the U.S. Environmental Protection Agency Greenhouse Gas Reporting Program, National Emissions Inventory, Discharge Monitoring Reports, and Toxic Release Inventory together with process unit capacities and fuel consumption data from the U.S. Energy Information Administration (U.S. EIA). The variability of refinery subprocess release factors is characterized using log-normal distributions with parameters set based on the distribution of release factors across facilities. The U.S. EPA Tool for the Reduction and Assessment of Chemical and Environmental Impacts life cycle impact assessment (LCIA) method is used together with the updated inventory data to provide impact potentials in the PRELIM dashboard interface. Release inventories at the subprocess level enable greater responsiveness to variable selection within PRELIM, such as refinery configuration, and allocation to specific refinery products. The updated version also provides a template to allow users to import PRELIM inventory results into the openLCA software tool as unit process data sets. Here we document and validate the model updates. Impact potentials from the national crude mix in 2014 are compared to impacts from the 2005 mix to demonstrate the impact of assay and configuration on the refining sector over time. The expanded version of PRELIM offers users a reliable, transparent, and streamlined tool for estimating the effect of changes in petroleum refineries on LCIA results in the context of policy analysis.

Environmental and Operational Performance of CO2-EOR as a CCUS Technology: A Cranfield Example with Dynamic LCA Considerations

This study evaluates the potential of carbon dioxide-enhanced oil recovery (CO2-EOR) to reduce greenhouse gas emissions without compromising oil production goals. A novel, dynamic carbon lifecycle analysis (d-LCA) was developed and used to understand the evolution of the environmental impact (CO2 emissions) and mitigation (geologic CO2 storage) associated with an expanded carbon capture, utilization and storage (CCUS) system, from start to closure of operations. EOR operational performance was assessed through CO2 utilization rates, which relate usage of CO2 to oil production. Because field operational strategies have a significant impact on reservoir engineering parameters that affect both CO2 storage and oil production (e.g., sweep efficiency, flood conformance, fluid saturation distribution), we conducted a scenario analysis that assessed the operational and environmental performance of four common and novel CO2-EOR field development strategies. Each scenario was evaluated with and without stacked saline carbon storage, an EOR/storage combination strategy where excess CO2 from the recycling facility is injected into an underlying saline aquifer for long-term carbon storage. The dynamic interplay between operational and environmental performance formed the basis of our CCUS technology analysis. The results showed that all CO2-EOR evaluated scenarios start operating with a negative carbon footprint and, years into the project, transitioned into operating with a positive carbon footprint. The transition points were significantly different in each scenario. Water-alternating-gas (WAG) was identified as the CO2 injection strategy with the highest potential to co-optimize EOR and carbon storage goals. The results provide an understanding of the evolution of the system’s net carbon balance in all four field development strategies studied. The environmental performance can be significantly improved with stacked storage, where a negative carbon footprint can be maintained throughout the life of the operation in most of the injection scenarios modelled. This information will be useful to CO2-EOR operators seeking value in storing more CO2 through a carbon credit program (e.g., the 45Q carbon credit program in the USA). Most importantly, this study serves as confirmation that CO2-EOR can be operationally designed to both enhance oil production and reduce greenhouse gas emissions into the atmosphere.

Infrastructure to enable deployment of carbon capture, utilization, and storage in the United States

In February 2018, the United States enacted significant financial incentives for carbon capture, utilization, and storage (CCUS) that will make capture from the lowest-capture-cost sources economically viable. The largest existing low-capture-cost opportunity is from ethanol fermentation at biorefineries in the Midwest. An impediment to deployment of carbon capture at ethanol biorefineries is that most are not close to enhanced oil recovery (EOR) fields or other suitable geological formations in which the carbon dioxide could be stored. Therefore, we analyze the viability of a pipeline network to transport carbon dioxide from Midwest ethanol biorefineries to the Permian Basin in Texas, which has the greatest current carbon dioxide demand for EOR and large potential for expansion. We estimate capture and transport costs and perform economic analysis for networks under three pipeline financing scenarios representing different combinations of commercial and government finance. Without government finance, we find that a network earning commercial rates of return would not be viable. With 50% government financing for pipelines, 19 million tons of carbon dioxide per year could be captured and transported profitably. Thirty million tons per year could be captured with full government pipeline financing, which would double global anthropogenic carbon capture and increase the United States' carbon dioxide EOR industry by 50%. Such a development would face challenges, including coordination between governments and industries, pressing timelines, and policy uncertainties, but is not unprecedented. This represents an opportunity to considerably increase CCUS in the near-term and develop long-term transport infrastructure facilitating future growth.

Updating the U.S. Life Cycle GHG Petroleum Baseline to 2014 with Projections to 2040 Using Open-Source Engineering-Based Models

The National Energy Technology Laboratory produced a well-to-wheels (WTW) life cycle greenhouse gas analysis of petroleum-based fuels consumed in the U.S. in 2005, known as the NETL 2005 Petroleum Baseline. This study uses a set of engineering-based, open-source models combined with publicly available data to calculate baseline results for 2014. An increase between the 2005 baseline and the 2014 results presented here (e.g., 92.4 vs 96.2 g CO₂e/MJ gasoline, + 4.1%) are due to changes both in modeling platform and in the U.S. petroleum sector. An updated result for 2005 was calculated to minimize the effect of the change in modeling platform, and emissions for gasoline in 2014 were about 2% lower than in 2005 (98.1 vs 96.2 g CO₂e/MJ gasoline). The same methods were utilized to forecast emissions from fuels out to 2040, indicating maximum changes from the 2014 gasoline result between +2.1% and -1.4%. The changing baseline values lead to potential compliance challenges with frameworks such as the Energy Independence and Security Act (EISA) Section 526, which states that Federal agencies should not purchase alternative fuels unless their life cycle GHG emissions are less than those of conventionally produced, petroleum-derived fuels.

Life cycle assessment of carbon capture and utilization from ammonia process in Mexico

Post-combustion CO₂ capture (PCC) of flue gas from an ammonia plant (AP) and the environmental performance of the carbon capture utilization (CCU) technology for greenhouse gas (GHG) emissions to an enhanced oil recovery (EOR) system in Mexico was performed as case study. The process simulations (PS) and life cycle assessment (LCA) were used as supporting tools to quantify the CO₂ capture and their environmental impacts, respectively. Two scenarios were considered: 1) the AP with its shift and CO₂ removal unit and 2) Scenario 1 plus PCC of the flue gas from the AP primary reformer (AP-2CO₂) and the global warming (GW) impact. Also, the GW of the whole of a CO₂-EOR project, from these two streams of captured CO₂, was evaluated. Results show that 372,426 tCO₂/year can be PCC from the flue gas of the primary reformer and 480,000 tons/y of capacity from the AP. The energy requirement for solvent regeneration is estimated to be 2.8 MJ/kgCO₂ or a GW impact of 0.22 kgCO_2e/kgCO₂ captured. GW performances are 297.6 kgCO_2e emitted/barrel (bbl) for scenario one, and 106.5 kgCO_2e emitted/bbl for the second. The net emissions, in scenario one, were 0.52 tCO_2e/bbl and 0.33 tCO_2e/bbl in scenario two. Based on PS, this study could be used to evaluate the potential of CO₂ capture of 4080 t/d of 4 ammonia plants. The integration of PS-LCA to a PCC study allows the applicability as methodological framework for the development of a cluster of projects in which of CO₂ could be recycled back to fuel, chemical, petrochemical products or for enhanced oil recovery (EOR). With AP-2CO_2, "CO₂ emission free" ammonia production could be achieved.