Global warming poses a major challenge that humanity will face during the 21^st century, requiring a significant reduction in anthropogenic CO₂ emissions to mitigate the escalating global temperature. Several governments worldwide, including Brazil, have committed to achieving net-zero CO₂ emissions by 2050, which will be impossible without Carbon Capture, Utilisation and Storage (CCUS) deployment. Ranked 12^th globally in CO₂ emissions (and 1^st in South America), Brazil is in the early stages of studying CCUS. At present, CCUS efforts in the country primarily revolve around enhanced oil recovery, with limited exploration of CO₂ injection in alternative geological settings. A total of 31 sedimentary basins span Brazilian territory, encompassing an area of approximately 6.4 million km², 75% of which is situated onshore. The potential for CO₂ storage in saline aquifers is gaining attention globally, proving a successful and effective approach in various sites. In this work we combine the available surface (geological maps, roads, and gas pipelines) and subsurface data (seismic lines and borehole data) to assess the logistics and feasibility of utilizing saline formations in onshore intracratonic basins as CO₂ sinks, aiming to enable Brazil to reach net-zero CO₂ emissions by 2050. Previous studies indicate that the Parnaíba, São Francisco, Amazonas, and Paraná basins present saline formations with favorable characteristics for CO₂ injection, such as adequate depths, porosity, and permeability. Building upon prior research, we introduce the onshore portion of Espírito Santo Basin to the list of potential sinks, where the target saline aquifer is the pre-salt Mucuri Formation. Results show that greenhouse gases emissions from industrial processes are notably higher in the southeast region of Brazil. Within this region, two formations exhibit considerable potential for carbon sequestration in saline aquifers: (i) the Mucuri Formation, located in the onshore Espírito Santo Basin, reaching 350 m of thickness and shallowest depths of about 950 m, and (ii) the Rio Bonito Formation, in the proximities of the São Paulo state, with over 100 m of thickness and shallowest depths of about 650 m. For large-scale projects, CO₂ transport in the region can be accomplished using the available infrastructure and the available gas pipelines, while smaller-scale research projects can utilize trucks, rail, and ships. Brazil's untapped potential for CCUS presents a unique funding opportunity from the private sector, marking a crucial step toward sustainable and impactful climate action.

How to cite: B. Amarante, F., Kuchle, J., and B. Haag, M.: Towards net-zero: assessing the carbon storage potential of onshore saline aquifers in Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-362, https://doi.org/10.5194/egusphere-egu24-362, 2024.

In the context of Carbon Capture and Storage (CCS), the porosity of potential storage formations is a critical factor. Our study explores this aspect using computed tomography (CT) to assess how different scanning resolutions impact the accuracy of porosity measurements. We employed three CT systems - Geotek RXCT (resolution ~20-150 μm), Bruker 1272 (resolution ~5 μm), and DELab μCT-100 (resolution ~9 μm) - to scan sandstone cores of varying porosities. The aim was to identify an optimal scanning resolution that balances detail with practicality for CCS evaluations.

This research addresses the challenges in high-resolution CT scanning, such as denoising effects that can alter accuracy, and the complexities of thresholding segmentation across various systems. Additionally, we examined the partial volume effect, crucial for interpreting pore sizes and distributions accurately.

Our preliminary results suggest that scanning resolution significantly affects the perceived porosity. Different resolutions uncover diverse aspects of pore structure, highlighting the importance of choosing an appropriate resolution. Advanced image processing techniques, including effective denoising and accurate thresholding, are vital for reducing errors in porosity measurement.

The study provides valuable insights into the use of CT scanning for CCS applications, emphasizing the need for a balanced approach in resolution selection and sophisticated image processing. These findings are instrumental in enhancing the reliability of geological evaluations for potential CCS sites, contributing to the broader efforts in carbon storage and climate change mitigation.

How to cite: Huang, J.-J. S., Liou, Y.-M., Kioka, A., and Yang, T.-R.: Exploring the Relationship between CT Scanning Resolutions and Sandstone Porosity for CCS Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12846, https://doi.org/10.5194/egusphere-egu24-12846, 2024.

Natural gas storage is currently considered as one key pillar of the EU strategy to ensure security of energy supply. In view of CH₄ storage, Oldenburg [1] demonstrated in a theoretical study that using CO₂ as cushion gas instead of CH₄ has the advantage of increasing natural gas storage capacities of geologic reservoirs by up to 30 %. This is due to CO₂ undergoing a significant density change when its’ critical pressure is exceeded during CH₄ injection. Kühn et al. [2] investigated a comparable scenario with CH₄ gas storage in a closed cycle with CO₂ in one reservoir to temporarily store and reuse wind and solar energy. However, the potential qualitative degradation of the stored CH₄ due to mixing with the CO₂ cushion gas has not yet been sufficiently addressed in terms of the impact of the modeller’s choice of diffusion coefficients. Hence, the present study focuses on a quantitative assessment of the mixing behaviour of CH₄ and CO₂ under consideration of dynamic binary diffusion coefficients in a reference numerical simulation benchmark [1,3]. The TRANSPORTSE numerical simulator [4,5] is used with dedicated measures to mitigate the initially high numerical dispersion, introduced by the benchmark’s relatively coarse grid discretisation. The simulation results show that the mixing region is substantially reduced if dynamic binary diffusion coefficients are applied instead of a global constant for both gas components. Consequently, it is demonstrated that previous numerical assessments of natural gas storage with a carbon dioxide cushion gas overestimate the simulated CH₄-CO₂-mixing area, and thus the calculated mixing losses. Hence, combined gas storage of CH₄ and CO₂ is more efficient than expected so far.

[1] Oldenburg, C. M. (2003) Carbon Dioxide as Cushion Gas for Natural Gas Storage. Energy Fuels 17(1), 240−246. https://doi.org/10.1021/ef020162b

[2] Kühn, M., Nakaten, N. C., Streibel, M., Kempka, T. (2014): CO2 Geological Storage and Utilization for a Carbon Neutral “Power-to-gas-to-power” Cycle to Even Out Fluctuations of Renewable Energy Provision. Energy Procedia, 63, 8044-8049. https://doi.org/10.1016/j.egypro.2014.11.841

[3] Ma, J., Li, Q., Kempka, T., Kühn, M. (2019) Hydromechanical Response and Impact of Gas Mixing Behavior in Subsurface CH4 Storage with CO2-Based Cushion Gas Energy & Fuels 33 (7), 6527-6541. https://doi.org/10.1021/acs.energyfuels.9b00518

[4] Kempka, T. (2020) Verification of a Python-based TRANsport Simulation Environment for density-driven fluid flow and coupled transport of heat and chemical species. Advances in Geosciences, 54, 67-77. https://doi.org/10.5194/adgeo-54-67-2020

[5] Kempka, T., Steding, S., Kühn, M. (2022) Verification of TRANSPORT Simulation Environment coupling with PHREEQC for reactive transport modelling. Advances in Geosciences, 58, 19-29. https://doi.org/10.5194/adgeo-58-19-2022

How to cite: Kempka, T. and Kühn, M.: Geologic CH4 storage with CO2 cushion gas: using dynamic binary diffusion coefficients instead of a global constant in numerical simulations is more precise and results in lower mixing losses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17184, https://doi.org/10.5194/egusphere-egu24-17184, 2024.

In recent years there has been rapid development of nanoparticles (NPs). Nanoparticles can be used both as a probe into restricted spaces, such as the pores within a reservoir rock, and as tools for altering wettability or deliberately blocking pore throats to enhance fluid movement in less connected pores. Silica nanoparticles can have functional surfaces allowing them to react specifically to oils or water. Nanoparticles can be used to enhance oil production by releasing oil on mineral surfaces and improving fluid flow. However, they also have the potential for improving CO₂ flow in CCUS reservoirs while enhancing the pore volume available for CO₂ storage. In this paper we evaluate the performance of different non-functionalised and functionalised nanoparticles for enhancement of oil production, CO₂ emplacement and gas flow. Different forms of silica NPs have been made, either unfunctionalized, or functionalised with branched amino-based polymer (hydrophilic) or a silane-based agent (hydrophobic). Their stability has been characterised using a range of laboratory methods. The microscopic performance of the nanoparticles has been measured using contact angle measurements. Their ability to enhance oil production and CO₂ emplacement has been tested using imbibition and drainage experiments. 

The contact angles, measured in the presence of brine, no modified silica NPs, branched amino-based polymer (hydrophilic) modified silica NPs and silane-based agent (hydrophobic) modified silica NPs showed contact angle values of approximately 110°, 116°, 124°, and 136°, respectively. These results show that introduction of nanofluids led to a change in substrate wettability from water-wet to strongly water-wet. Notably amongst the tested nanoparticles the Silane-based NPs demonstrated the highest hydrophilic surface. The spontaneous imbibition tests conducted on various sandstone cores revealed that silane-based NPs yielded the highest oil recovery rates among the tested NPs. Specifically, these nanoparticles showed an approximate 12% and 50% enhancement in oil recovery compared to non-modified silica nanoparticle, and branched amino-based polymer (hydrophilic) modified silica NPs. In summary, nanofluids have been shown to substantially improve the wettability alteration of the rock surface from oil-wet to water-wet, which can lead to improve the volume and flow characteristics of legacy CCUS prospects. Our future plan is to investigate the enhancement of carbon dioxide (CO₂) solubility in brine through the utilization of the prepared nanoparticles, with the objective of advancing carbon capture technologies.

How to cite: Tliba, L., Hetnawi, A., Sagala, F., Menzel, R., Glover, P., and Hassanpour, A.: Characterising functionalised nanoparticles for improving fluid flow for CCUS in legacy hydrocarbon reservoirs , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13835, https://doi.org/10.5194/egusphere-egu24-13835, 2024.

Abstract: Fractured carbonate reservoirs are of great importance in the oil industry due to their significant role in global oil reserves and complex nature, where the majority of these reservoirs are naturally fractured, making them complex and challenging for oil recovery. The detection and characterization of fractures are essential for understanding the reservoir's petrophysical properties and hydrocarbon recovery potential as they play a critical role in reservoir performance. In this paper we have used 3D seismic from the Razzak field in the Western Desert, Egypt, with a specific focus on the Alamein dolomite reservoir. The reservoir holds significance due to its prolific oil-bearing nature, and featuring widespread lateral distribution in the northern Western Desert. Additionally, its contribution to an active Mesozoic petroleum system emphasizes its importance. Using Petrel software, the Alamein top and visible faults were identified, leading to the creation of a structural map illustrating the WSW-ENE axes of the Alamein's structural culminations in the southern part of the horst block. Owing to an extensional force during the Jurassic period with a NE-SW orientation, resulting from rifting, was evident, marked by the formation of normal faults associated with the opening of the Neotethys in the NE-SW direction. In the interpretation of 3D seismic data for Alamein dolomite reservoir, only one major listric normal fault was identified. However, the presence of minor faults or fractures, not easily discernible with conventional seismic techniques, is plausible. To address this, volume attributes were applied to detect subtle changes in seismic properties: (i) the curvature operation calculated the dip and azimuth angles, aiding in identifying structural complexities like faults and fractures, (ii) the maximum curvature value highlighted areas of steeply dipping or folded structures, (iii) Edge detection emphasized sharp boundaries, yet no hidden fractures or minor faults were revealed. The variance attribute yielded limited information, but Ant tracking on the variance cube effectively identified hidden minor faults and fractures. Incorporating the Ant track attribute into FRACPAQ software provided an objective methodology for quantifying fracture patterns, revealing NW-SE-oriented fracture segments in contrast to the WSW-ENE orientation of the major fault. Consequently, seismic attributes will unveil concealed fractures, and the application of FRACPAQ will prove effective in furnishing data on fracture orientation and length statistics.

Key words: FracpaQ; seismic attributes; fractured carbonate; Razzak field

How to cite: Elattar, H.A., Collier, R., and Glover, P. W. J.: Using FracPaQ and seismic attributes to assess seismic scale fractures in carbonate reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1674, https://doi.org/10.5194/egusphere-egu24-1674, 2024.

How to cite: Elattar, H., Collier, R., and Glover, P. W. J.: Using FracpaQ and seismic attributes to assess seismic scale fractures in carbonate reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1674, https://doi.org/10.5194/egusphere-egu24-1674, 2024.

To meet the climate targets outlined in the Paris Agreement, European Green Deal, and the goal of reducing dependence on fossil fuel imports per the REPower EU Action, decarbonizing and reducing energy consumption in the heating and cooling sector is imperative. This sector, a major contributor to household energy use, plays a pivotal role in achieving sustainable energy goals.

Geothermal energy, particularly through geothermal doublets, stands out as an ideal solution for supplying energy for space heating and cooling. However, the inherent risks associated with fluid exchange with the subsurface make it scientifically or politically challenging in certain areas. Addressing this concern, deep borehole heat exchangers function as closed-loop systems, eliminating fluid exchange with the subsurface.

In this study, we explore the feasibility of repurposing existing oil and gas wells in the Northern Netherlands as deep coaxial borehole heat exchangers to provide heat to local communities. Utilizing analytical solutions, we calculate the thermal power output of 365 gas wells suitable for retrofitting. These wells exhibit bottom hole temperatures exceeding 80°C, capable of delivering temperatures above 60°C or thermal powers exceeding 800 kW, depending on flow rate and inflow temperature.

Our analysis includes assessing the proximity of well locations to high-density heat demand neighborhoods within a 6 km radius, facilitating the provision of supply temperatures for future local heat district networks. Notably, heat loss from well to neighborhood generally remains below 2°C, ensuring sufficient heating power supply to nearby residential areas. Several well clusters demonstrate significant heat over-supply, suggesting the potential for transporting excess heat to more distant locations. In cases where heat supply from wells is too low, in particularly in neighbourhoods with very low building efficiency rating (<E), heat pumps can be utilised to supply the needed energy.

Our findings indicate that repurposing existing hydrocarbon wells as coaxial heat exchangers offers a viable option for providing low-carbon heating to numerous residential areas in the Northern Netherlands. However, the geographical distribution reveals that not all high heat demand neighbourhoods have well sites in proximity, underscoring the importance of implementing a diverse heat supply strategy.

How to cite: Miocic, J., Drenth, J., and van Benthem, P.: Reutilising hydrocarbon wells as deep heat exchangers to decarbonise heating in the Northern Netherlands , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7761, https://doi.org/10.5194/egusphere-egu24-7761, 2024.

Since the end of the XIX century, many wells have been drilled worldwide for both Oil & Gas exploration purposes. Most of them are now abandoned and subjected to mining closure because exhausted or sterile. In the new epoch of energy transition scenario, the possibility to adapt and reuse these existing boreholes to exploit geothermal energy seems very promising. In fact, considering that approximately 40% of the total costs for a new geothermal project are devoted to drilling activity, the possibility of repurposing abandoned oil and gas wells offers a wide range of applications and exploitation of underground heat uses. The drilled borehole available data (e.g., underground temperature, lithology) provide helpful information about the sub-surface reservoirs, reducing the mining risk level, and wells allow direct access to the sub-surface heat energy. However, to develop a commercially viable geothermal power/thermal generating system, one must consider several factors, i.e., available prospecting, drilling and reservoir technologies, energy costs in the area, and resource durability.

This research aims to analyze the potential and feasibility of deep closed-loop systems solutions for heat and power energy production in Italy, in areas characterized by both normal and anomalous geothermal gradients and the distribution of available abandoned oil and gas wells. A prominent result is the development of a workflow leading to the feasibility assessment of deep closed-loop systems development, based on the identification of suitable abandoned O&G wells through the geological and thermal underground characterization and wells construction characteristics (diameter, depth, borehole material). Furthermore, a sensitivity analysis of the main parameters affecting most of the retrofitting of abandoned wells for geothermal purposes is performed thanks to thermal FEM modelling.

Finally, identifying the possible end-users in a suitable case study area, this research work provides preliminary insights into the quantity of thermal energy and electric power that this technology could produce.

How to cite: Facci, M. and Galgaro, A.: Numerical sensitivity analysis of energy performance of geothermal deep closed loop heat exchangers derived from the reuse of abandoned oil and gas wells, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17674, https://doi.org/10.5194/egusphere-egu24-17674, 2024.

With the advancement of exploration theory and technology, deep and ultra-deep carbonate rocks have gradually become an important new field for the development of oil and gas resources. High-quality carbonate reservoirs have become the focus of attention for oil and gas exploration and research in deep and ultra-deep fields. The Tarim Basin is the largest intracontinental oil and gas basin in China. The thick carbonate strata developed in the Lower Paleozoic are the main layers for oil and gas exploration, and the Ordovician carbonate strata are the main oil and gas producing layers. The predecessors have studied the tectonic evolution, sedimentary background and rock types of the Ordovician in the Tarim Basin. Combined with the analysis of the sedimentary thickness, lithology distribution and seismic profile structure of the Early Ordovician, it is believed that the Lower Ordovician sedimentary period inherited the Cambrian sedimentary pattern and transformed it into a gentle slope sedimentary background with a 'uplift-sag 'pattern, with obvious differentiation. Under the sedimentary background of the gentle slope of the Penglaiba Formation, the three paleo-uplifts of southwestern, northern and central Tarim are inherited geomorphological highs, and the inner gentle slope tidal flat facies is developed. The thickness of the stratum is obviously thinner, and it is mainly developed to represent the tidal flat environment. The periclinal part around the paleo-uplift is the middle gentle slope, which is characterized by dolomite and limestone interbeds. The proportion of granular rocks is high, which is a favorable development area for granular beaches. In this study, the deep drilling cores of the Lower Ordovician Penglaiba Formation in the central Tarim Basin were taken as the key research object, and the lithofacies, reservoir characteristics and dominant reservoir control factors of dolomite reservoirs were systematically analyzed by using macro-micro, qualitative-quantitative reservoir petrology analysis methods. Through research, it is clear that the rock types of the Lower Ordovician Penglaiba Formation in the central Tarim Basin are mainly crystalline dolomite and ( residual ) granular dolomite, and also contain a small amount of limestone, siliceous rocks and transitional rocks. There are various types of reservoir space, mainly including non-fabric selective dissolution pores, intercrystalline pores and various fractures. Combined with previous studies on the genesis and diagenetic evolution of the Lower Ordovician dolomite in the Tarim Basin, it is considered that the development of high-quality dolomite reservoirs in the Lower Ordovician Penglaiba Formation in the central part of Tarim Basin is controlled by many factors. It is the result of a combination of favorable sedimentary facies belts, short-term sea-level changes, exposure and dissolution, early dolomitization, and late tectonic hydrothermal adjustment and transformation.

How to cite: Li, X. and Xu, Q.: Development characteristics and controlling factors of deep dolomite reservoirs of Lower Ordovician in Tazhong area, Tarim Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20142, https://doi.org/10.5194/egusphere-egu24-20142, 2024.

Despite constituting two-thirds of the sedimentary rock volume, shales are a few of the least understood rocks. The varied depositional processes and environments give rise to complexity and anisotropy in them. Understanding unconventional resources like shales becomes crucial given their abundance in the petroleum systems and reservoirs and their potential suitability for sub-surface carbon and radioactive waste storage. Therefore, paramount significance lies in understanding the petrophysical and rock physical characteristics of shales to develop feasibility models for the sustainable use of these rock types.
 
This investigation focuses on the Barren Measures and Raniganj Formation shales in the Damodar Valley of Eastern India, which are primarily rich in clays, carbon, and iron and are of fluvio-lacustrine origin. These relatively shallow formations can be good sites for storage and sequestration as they are overlain by shaley and clayey formations acting as traps. The anisotropy in shales is even more challenging as its imponderables range from a micro to a macro scale. This changes even further with factors like organic-hosted porosity and maturity. The inherent anisotropy in shales necessitates a multiscale examination. These multiscale discontinuities, coupled with parameters like organic matter and maturity, impact the elastic properties of the rocks, as evidenced by the ultrasonic evaluations.
 
In this study, acoustic characterization of samples was conducted using a benchtop ultrasonic wave propagation setup. The samples were clustered based on their colour and observed megascopic properties. Some sandstones were also included in the study to contrast sandstones with respect to shales. The wave velocities were determined for samples subjected to progressive heating up to 200°C (gas window), and the consecutive changes in the elastic parameters and resultant wave velocities of the rock were studied. Inputs from other methods utilizing different physics, such as FE-SEM, XRD were integrated to refine our interpretation. Notable changes were seen in wave velocities, especially in clusters with elevated organic content, while the density and Vp cross plots gave a good correlation with an R² value of around 0.7.
This study advances our understanding of the impact of temperature on the elastic properties of shales, an aspect less explored than factors like stress and pressure. Thoroughly characterizing these parameters through acoustic methods provides critical insights into shale's storage capacity, carbon sequestration potential, and additional hydrocarbon recovery, specifically with respect to the Damodar Valley shales, aiding India to offset the projected peak of 4 GT CO₂ emissions to achieve the carbon neutral goal promised at COP 26 and fulfilling UN Sustainable Development Goals.

How to cite: Jamwal, V. D. and Sharma, R.: Ultrasonic Evaluation of Shales vis-à-vis Temperature: A Case Study from Permian Damodar Valley Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-800, https://doi.org/10.5194/egusphere-egu24-800, 2024.

Carbon capture and storage technology is a necessary means to achieve the temperature control goal of 1.5 degrees Celsius under the background of peak carbon dioxide emissions and carbon neutrality. The storage of carbon dioxide in oil and gas reservoirs has the advantages of high safety, large storage capacity, and less additional cost. The reservoir-caprock configuration can provide favorable space for the storage of carbon dioxide geological bodies. To make clear the distribution range of geological bodies suitable for carbon dioxide sequestration, taking the middle-south section of the eastern sag of Liaohe as an example, based on the model of the ratio of mud to ground and caprock effectiveness division, the control factors of caprock sealing were analyzed by entropy weight method combined with TOPSIS method, and the effective thickness of reservoir was determined by clarifying the relationship between reservoir lithology, physical properties, oil content and electricity. The results show that the lower limit of the effective caprock mud-to-ground ratio in the sand-mud interbedding sequence is 70.6%, and the sealing ability of caprock is mainly affected by the thickness of the fault and the thickness of the caprock single layer; The two sets of caprocks in the Shahejie Formation and Dongying Formation are relatively stable, with good fault-caprock configuration sealing, and the fault juxtaposition thickness in the Shahejie Formation is characterized by "thick in the north and thin in the south"; The effective reservoirs of the Dongying Formation are distributed in the whole region, the effective reservoirs of Es1 are distributed in the north of Rongxingtun, and the distribution range is smaller than that of the Dongying Formation, while the effective reservoirs of Es3 are mainly distributed in Huangyure area at the northern end of the study area, and the distribution range is further reduced. According to the reservoir-caprock configuration, carbon dioxide storage types can be divided into three types: shallow storage type, deep storage type, and multi-layer storage type. The lower caprock is well sealed and the lower effective thick reservoir controls the deep enrichment of carbon dioxide; The lower caprock is poorly sealed, and the effective thick reservoir in the middle or upper part controls the multi-layer enrichment of carbon dioxide; The lower caprock is poorly sealed, the upper caprock is well sealed, and the upper effective thick reservoir controls the shallow enrichment of carbon dioxide. The relationship between the effective thickness of the reservoir and the sealing ability of the caprock determines the vertical distribution series of carbon dioxide.

How to cite: li, H. and jiang, Y.: Study on Reservoir-caprock Configuration for Carbon Dioxide Sequestration in oil and gas reservoirs , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-86, https://doi.org/10.5194/egusphere-egu24-86, 2024.

Recent years have seen the growth of new techniques that combine conventional stratigraphic and observational approaches to characterizing the type, scope, extent, timing and effects of diagenetic processes with petrophysical measurements of their rock microstructure. These Quantitative Diagenetic (QD) techniques can be used to predict post- and pre-dolomitisation porosities and permeabilities as well as trace the pathway of the diagenetically evolving rock through different stages of diagenesis that may turn a low-quality carbonate reservoir into a high-quality reservoir, or vice versa. While these new QD techniques are becoming useful for the characterization of hydrocarbon reservoirs, they are also extremely useful in the characterization of carbonate reservoirs for prospective CCUS use. This paper will briefly explain some of the main approaches to QD including dolomitisation prediction, petrodiagenetic pathways, reservoir quality fields, and Fracture Effect Index (FEI), before examining how they can be used to ensure that the prospective CCUS target reservoir is sufficiently well characterized that effective reservoir modelling can take place, and that the volume, flow and trapping of CO₂ in the reservoir can be effectively monitored. Dolomitisation is known to be affected by the presence of CO₂, with CO₂ dissolving in aqueous pore fluids to form carbonic acid that directly affects porosity through dissolution and indirectly by affecting the dynamics of the dolomitisation process itself. There are two current QD methods for predicting the change in porosity upon dolomitisation. One is affected by both the direct and indirect effects, while the other is only sensitive to the indirect effects. Both the direct and the indirect effects can be plotted on a petrodiagenetic pathway. The presence of fractures is also a key aspect of how injected CO₂ will flow in a CCUS reservoir. The QD parameter FEI describes the change in permeability of a rock concomitant upon a unit change in fracture porosity (i.e., what increase in flow results from a given increase on fracture porosity). This varies depending upon the degree to which fractures are connected and can be extremely useful in predicting the flow of CO₂ within a fractured legacy carbonate CCUS prospect. In summary, QD approaches have the potential to provide those who need to characterise and model carbonate CCUS prospects with new and useful tools.

How to cite: Mohammed-Sajed, O., Rashid, F., Glover, P., Collier, R., and Lorinczi, P.:  Using Quantitative Diagenesis to characterise and understand carbonate CCUS prospects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3199, https://doi.org/10.5194/egusphere-egu24-3199, 2024.

Successful exploration of Permian shale gas in the Hongxing area has broadened shale gas exploration in the Sichuan Basin; however, the target layer is newly discovered, and reservoir research, which is key to shale gas exploration and development, is limited, thus restricting the screening and evaluation of the section containing the shale gas target layer. In this study, using organic carbon, whole-rock mineral analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and other experimental methods, and by systematically identifying different lithofacies, we clarified the organic‒inorganic composition and microscopic pore structure characteristics of Permian shales in different phases of the Hongxing area and revealed the main factors controlling high-quality reservoirs and favorable lithofacies types for exploration. The results show that the shale in the study area mainly features six types of lithofacies: high-carbon siliceous shale (RS), high-carbon mixed shale (RM), high-carbon calcareous shale (RC), high-carbon muddy shale (RCM), low-carbon muddy shale (LCM), and low-carbon calcareous shale (LC). Organic pores are mainly present in RS, RM, RC, and RCM, while inorganic pores are dominant in LC and LCM. The pores are dominantly micropores, some mesopores are present, and very few macropores are present. Among them, the degree of micropore development is mainly affected by organic matter (abundance, maturity, and type), that of mesopores is mainly affected by clay minerals, and that of macropores is mainly affected by siliceous and clay minerals. There are obvious differences in the pore structure of different lithologies. The RS has the highest pore volume and specific surface area, with average values of 13.8×10^-3 cm³/g and 21.57 m²/g, respectively, and its pore morphology is ink-bottle type, with pore diameters mainly <10 nm. The storage space of RM, RC, RCM, and LCM is moderate, with low-carbon argillaceous shale (LM) having the lowest.

How to cite: Li, B., Zhou, N., and Lu, S.: Characteristics and factors controlling Permian shale gas reservoirs in the Hongxing area, Sichuan Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3700, https://doi.org/10.5194/egusphere-egu24-3700, 2024.

The changes in land use/cover are essential aspects of studying the impact of human activities on the Earth's surface and global transformations. In this study, utilizing the ESRI Global Land Cover data (ESRI land cover 2020) and the China Land Cover Data (CLCD), along with historical imagery from Google Earth, a comparative analysis scheme for land use classification results was designed. The CLCD dataset was updated, leading to the creation of a land use dataset for the Pan-Pearl River Basin spanning from 1985 to 2020. This dataset was then employed for the analysis of land use changes in the Pan-Pearl River Basin over the past 35 years.The results indicate:(1) Among the seven land use types, the most significant changes in area occurred in the following order: build -up land, cropland, forest land, grassland, shrubland, waterbody, and barren. Notably, there was a substantial increase in the areas of build-up land and forest land, while cropland, grassland, and shrubland experienced significant decreases. The waterbody’area showed a slight overall increase trend.(2) The major land use types undergoing changes varied among sub-basins, with the intensity of land use change ranked as follows: Pearl River Delta region(1.9%) > Coastal rivers in southern Guangdong and western Guangxi(0.20%) > Dongjiang River Basin(0.13%) > Hanjiang River Basin(0.12%) > Xijiang River Basin(0.10%) > Beijiang River Basin(0.08%) > Hainan Island region(0.02%).(3) Within the sub-basins of the Pan-Pearl River Basin, the most significant increase was observed in the area of built-up land, exhibiting a continuous expansion trend with a total increase of 12184 km². This increase was primarily due to the conversion of cropland, forest land, and waterbody. The most significant decrease occurred in cropland, with a total reduction of 10435 km², mainly transitioning to built-up land and forest land. The phenomenon of built-up land encroaching on cropland was particularly prominent, especially in the Pearl River Delta region. Forest land also showed a decreasing trend, mainly attributed to cultivation and the encroachment of built-up land. The reduction in grassland area was more pronounced in the Xijiang River Basin, primarily transforming into forest land, cropland, and built-up land. The study reveals that the rapid development of socio-economics and industry, coupled with an increase in residents' consumption levels, serves as the primary driving force behind land use changes in the Pan-Pearl River Basin. Additionally, land use and management policies play a crucial role as driving factors in the region's land use changes. This research aims to provide a scientific basis for formulating policies related to the region's land resources and land management, holding significant importance for preserving ecological balance and fostering sustainable development in the basin.

How to cite: Fan, W. and Yang, X.: Land Use Change Characteristics in the Pan-Pearl River Basin in China from 1985 to 2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7216, https://doi.org/10.5194/egusphere-egu24-7216, 2024.

          It is pivotal to predict the overall composition of subsurface oil and gas reservoirs to assess their fluidity, phase behavior, and recovery potential. Recognizing the significance of n-alkanes as key constituents of mature oil and gas, this study conducted a thermal simulation experiment of gold tube hydrocarbon generation on the source rock of Gulong Sag. The experiment included comprehensive analysis and measurement of the n-alkanes components in a representative sample. Subsequently, an empirical regression evaluation formula was established to evaluate the n-alkanes composition at various maturity stages. Furthermore, a chemical dynamics model for the formation of individual n-alkanes single molecule components was developed and calibrated based on the principles of chemical kinetics. Combined with the stratigraphic burial history and thermal evolution history of the target area, the distribution and evolution characteristics of n-alkanes components in different evolutionary stages of geological conditions can be quantitatively evaluated and predicted. Moreover, the phase behavior of n-alkanes components can be determined based on the evolution characteristics of these components. Experimental results indicate that the methane yield continues to increase with temperature under both heating rates. Additionally, the yield of n-C to n-C initially reaches its maximum with the temperature increase, and subsequently decreases. Furthermore, the hydrocarbon generation characteristics of n-alkanes follow a Gaussian distribution trend. The kinetic results demonstrate that the activation energy of n-alkanes falls within the range of 190-280 kJ/mol, while the distribution of pre-exponential factors is uneven. By considering the geological conditions, it has been determined that the light component in the Gulong Sag is currently experiencing a favorable generation period, whereas the heavy component has reached its peak formation stage, with some undergoing cracking. The oil and gas produced under these geological conditions exist as single-phase unsaturated fluids within volatile reservoirs. The evaluation value of the experimental regression formula, along with the predicted value from the dynamic model, aligns well with the experimental data, providing a solid foundation for the geological application of the model. Therefore, this research serves as a stepping stone towards furthering our understanding of hydrocarbon composition prediction, as well as evaluating phase behavior, mobility, and recovery of underground oil and gas in conjunction with geological conditions. 

How to cite: Bo, S., Xue, H., and Lu, S.: Simulation experiment evaluation and chemical kinetics prediction of the composition of n-alkanes components, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3696, https://doi.org/10.5194/egusphere-egu24-3696, 2024.