Pub Date : 2025-12-01Epub Date: 2025-11-28DOI: 10.1016/j.petlm.2025.11.006
Okorie Ekwe Agwu , Saad Alatefi , Muhammad Aslam Md Yusof , Cosmas Brendan Orun
Equivalent circulating density (ECD) denotes the density of drilling mud during circulation within a well. It is determined by integrating the equivalent static density with the pressure loss attributable to friction between the flowing mud and the geological formation. The effective management of ECD is imperative during drilling operations, as it plays a critical role in preventing kicks and minimising mud losses. Mud ECD has undergone extensive investigation through laboratory experiments, field measurements, and predictive modelling. Nevertheless, a comprehensive review of the various predictive models associated with ECD remains absent. The objective of this study is to review and critique existing correlations for estimating ECD. To accomplish this, a thorough bibliometric analysis was performed, focusing on peer-reviewed journals, mud manuals, and oil and gas conference papers. For the sake of clarity, existing models were categorized into tables, with their principal features highlighted. A critique of each model was subsequently provided. In total, 45 models related to ECD were identified, reviewed, and critiqued. The findings reveal that over 44% of the models are based on machine learning (ML), 27% are analytical models, 16% are regression based models, and 13% are simulator-related. Although there is no universally accepted model for ECD, there is an observable trend towards the utilization of ML algorithms for ECD estimation due to their predictive capabilities. However, the interpretability of these ML-based models remains a significant concern. This review serves as a comprehensive source of information on ECD for both readers and industry practitioners. Additionally, it directs researchers towards areas requiring further exploration and aids drilling professionals in selecting appropriate ECD models.
{"title":"Predicting drilling mud equivalent circulating density with precision: A critical review of modern approaches","authors":"Okorie Ekwe Agwu , Saad Alatefi , Muhammad Aslam Md Yusof , Cosmas Brendan Orun","doi":"10.1016/j.petlm.2025.11.006","DOIUrl":"10.1016/j.petlm.2025.11.006","url":null,"abstract":"<div><div>Equivalent circulating density (ECD) denotes the density of drilling mud during circulation within a well. It is determined by integrating the equivalent static density with the pressure loss attributable to friction between the flowing mud and the geological formation. The effective management of ECD is imperative during drilling operations, as it plays a critical role in preventing kicks and minimising mud losses. Mud ECD has undergone extensive investigation through laboratory experiments, field measurements, and predictive modelling. Nevertheless, a comprehensive review of the various predictive models associated with ECD remains absent. The objective of this study is to review and critique existing correlations for estimating ECD. To accomplish this, a thorough bibliometric analysis was performed, focusing on peer-reviewed journals, mud manuals, and oil and gas conference papers. For the sake of clarity, existing models were categorized into tables, with their principal features highlighted. A critique of each model was subsequently provided. In total, 45 models related to ECD were identified, reviewed, and critiqued. The findings reveal that over 44% of the models are based on machine learning (ML), 27% are analytical models, 16% are regression based models, and 13% are simulator-related. Although there is no universally accepted model for ECD, there is an observable trend towards the utilization of ML algorithms for ECD estimation due to their predictive capabilities. However, the interpretability of these ML-based models remains a significant concern. This review serves as a comprehensive source of information on ECD for both readers and industry practitioners. Additionally, it directs researchers towards areas requiring further exploration and aids drilling professionals in selecting appropriate ECD models.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 699-716"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research investigates the role of dispersion of nanoparticles in gas during gas recycling process to improve the gas condensate recovery via altering the carbonate reservoirs wettability. The nanoparticles were synthesized and analyzed using dynamic light scattering (DLS), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). After that, the dispersion of nanoparticles in methane was investigated by cloud point pressures measurement. Also, the effectiveness of methane/nanoparticles solutions was assessed through the contact angle experiments and gas recycling process. Based on the cloud point pressures results, the nanoparticles can be dispersed in methane at pressures commensurate with hydrocarbon reservoirs. Gas/nanoparticles single-phase solutions increased the contact angles of gas condensate and n-decane from 12° to 121° and 135.5°, respectively, for fluorinated silica, and to 100.5° and 108° for fluorinated titania. The shift from oil-wet to gas-wet conditions enhanced the recovery factor from 55% to 76%, marking a 21% improvement in gas condensate recovery during gas recycling. Furthermore, the pressure drop ratio decreased by 60%, due to better surface wettability and reduced condensate blockage. Comparative results indicated that the dispersion of fluorinated silica nanoparticles in gas outperformed fluorinated titania in altering wettability. These results emphasize the potential of current new approach, through dispersion of fluorinated nanoparticles in gas; to improve gas condensate recovery during gas recycling, especially in low-permeability carbonate reservoirs.
{"title":"Improving the gas condensate recovery through wettability alteration to gas-wet during gas recycling via dispersion of nanoparticles in gas","authors":"Naser Namdari Garaghani , Asghar Gandomkar , Amin Azdarpour","doi":"10.1016/j.petlm.2025.10.003","DOIUrl":"10.1016/j.petlm.2025.10.003","url":null,"abstract":"<div><div>This research investigates the role of dispersion of nanoparticles in gas during gas recycling process to improve the gas condensate recovery via altering the carbonate reservoirs wettability. The nanoparticles were synthesized and analyzed using dynamic light scattering (DLS), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). After that, the dispersion of nanoparticles in methane was investigated by cloud point pressures measurement. Also, the effectiveness of methane/nanoparticles solutions was assessed through the contact angle experiments and gas recycling process. Based on the cloud point pressures results, the nanoparticles can be dispersed in methane at pressures commensurate with hydrocarbon reservoirs. Gas/nanoparticles single-phase solutions increased the contact angles of gas condensate and n-decane from 12° to 121° and 135.5°, respectively, for fluorinated silica, and to 100.5° and 108° for fluorinated titania. The shift from oil-wet to gas-wet conditions enhanced the recovery factor from 55% to 76%, marking a 21% improvement in gas condensate recovery during gas recycling. Furthermore, the pressure drop ratio decreased by 60%, due to better surface wettability and reduced condensate blockage. Comparative results indicated that the dispersion of fluorinated silica nanoparticles in gas outperformed fluorinated titania in altering wettability. These results emphasize the potential of current new approach, through dispersion of fluorinated nanoparticles in gas; to improve gas condensate recovery during gas recycling, especially in low-permeability carbonate reservoirs.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 770-783"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates the torsional stick-slip behavior of steel and aluminum drill strings under varying levels of aggressiveness, which refers to the intensity with which the drill bit interacts with the rock formation. Aggressiveness is primarily influenced by critical factors such as torque on bit (TOB), weight on bit (WOB), and rotational speed (RPM). It is quantitatively expressed as the ratio of TOB to WOB, a key determinant in the drilling process that influences how effectively the bit penetrates the formation. A small-scale drill string model was developed and tested under varying aggressiveness and RPMs using a numerical simulator. The objective was to assess how the different materials respond to torsional stick-slip vibrations across a range of operational parameters. The simulations were conducted over 30 s intervals with both stable and varying RPMs, allowing for a detailed comparison of the material's dynamic behaviors. The RPM limits, which indicate the maximum RPM beyond which severe stick-slip occurs, were calculated for both materials. Results revealed that steel drill strings exhibited superior stability, with fewer torsional oscillations and shorter sticking periods, particularly at higher aggressiveness ratios. While aluminum drill strings, being lightweight, showed greater susceptibility to torsional oscillations, especially at lower rotational speeds, leading to longer periods of stick-slips. Also, as the aggressiveness reduces, the RPM limits for both materials increases. This emphasizes the importance of identifying optimal RPM limits and material selection to minimize vibrations and improve drilling efficiency.
{"title":"Optimizing drilling efficiency: Comparative study of stick-slip vibration of steel and aluminum drill strings","authors":"Chinedu Ejike , Khizar Abid , Chinedu J. Okere , Catalin Teodoriu","doi":"10.1016/j.petlm.2025.09.005","DOIUrl":"10.1016/j.petlm.2025.09.005","url":null,"abstract":"<div><div>This study investigates the torsional stick-slip behavior of steel and aluminum drill strings under varying levels of aggressiveness, which refers to the intensity with which the drill bit interacts with the rock formation. Aggressiveness is primarily influenced by critical factors such as torque on bit (TOB), weight on bit (WOB), and rotational speed (RPM). It is quantitatively expressed as the ratio of TOB to WOB, a key determinant in the drilling process that influences how effectively the bit penetrates the formation. A small-scale drill string model was developed and tested under varying aggressiveness and RPMs using a numerical simulator. The objective was to assess how the different materials respond to torsional stick-slip vibrations across a range of operational parameters. The simulations were conducted over 30 s intervals with both stable and varying RPMs, allowing for a detailed comparison of the material's dynamic behaviors. The RPM limits, which indicate the maximum RPM beyond which severe stick-slip occurs, were calculated for both materials. Results revealed that steel drill strings exhibited superior stability, with fewer torsional oscillations and shorter sticking periods, particularly at higher aggressiveness ratios. While aluminum drill strings, being lightweight, showed greater susceptibility to torsional oscillations, especially at lower rotational speeds, leading to longer periods of stick-slips. Also, as the aggressiveness reduces, the RPM limits for both materials increases. This emphasizes the importance of identifying optimal RPM limits and material selection to minimize vibrations and improve drilling efficiency.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 732-743"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-11-29DOI: 10.1016/j.petlm.2025.11.004
Junyu You , Xingxin Jiang , Xiaoliang Huang , Qiqi Wanyan , Ziang He , Songze Li , Hongcheng Xu
The construction and operation of gas reservoir-type underground gas storage (UGS) facilities play a pivotal role in ensuring the safety and stability of natural gas supply. For gas reservoirs with edge or bottom water, the subsurface gas-water two-phase flow dynamics and high-speed injection/withdrawal (I/W) processes result in complex distributions of gas and water within the reservoir layers. Additionally, the boundaries of multiphase flow zones are often poorly defined, and the pore volume utilization efficiency (PVUE), which directly impacts effective storage capacity, remains difficult to quantify. These challenges hinder the accurate evaluation of gas storage capacity and complicate the design of optimal construction and operational parameters for UGS facilities. To address these issues, this study proposes an integrated approach combining multi-cycle I/W experiments, numerical reservoir simulations, and the mass balance method to accurately assess UGS storage capacity. The methodology was applied to an active UGS facility constructed in a water-bearing gas reservoir in northwestern China. The gas-bearing reservoir was categorized into four distinct flow zones: the gas zone, the gas-displacing-water zone, the transition zone, and the water zone. Key factors influencing immobile gas-bearing pore volume—such as water invasion and stress sensitivity—were identified for each zone. A mathematical model was developed to predict immobile gas-bearing pore volume, and a quantitative model was established to estimate effective gas storage space (underground) by incorporating PVUE variations across different flow zones. These models provided theoretical foundations for designing UGS construction and operational strategies. The results demonstrated: (1) After six I/W cycles, the measured PVUE in the gas zone was 99.3% and 94.9% for blocks B1 and B2, respectively. In the gas-displacing-water zone, the PVUE was 80.9% and 73.8%, while in the transition zone, it was 47.9% and 40.3%. (2) The total gas-bearing pore volume of the UGS was 9.65 million rm3 (subsurface conditions), with an effective gas storage space of 5.39 million rm3 after accounting for PVUE variations across flow zones. (3) Numerical simulations confirmed that the proposed UGS operational design would achieve a total inventory of 8.24 × 108 sm3 (surface conditions) and an effective storage capacity of 6.67 × 108 sm3. This study provided a robust framework for evaluating and optimizing UGS storage capacity in water-bearing gas reservoirs, offering valuable insights for the design and operation of such facilities.
{"title":"A multi-zone characterization-based framework for effective storage capacity evaluation in water-bearing reservoirs","authors":"Junyu You , Xingxin Jiang , Xiaoliang Huang , Qiqi Wanyan , Ziang He , Songze Li , Hongcheng Xu","doi":"10.1016/j.petlm.2025.11.004","DOIUrl":"10.1016/j.petlm.2025.11.004","url":null,"abstract":"<div><div>The construction and operation of gas reservoir-type underground gas storage (UGS) facilities play a pivotal role in ensuring the safety and stability of natural gas supply. For gas reservoirs with edge or bottom water, the subsurface gas-water two-phase flow dynamics and high-speed injection/withdrawal (I/W) processes result in complex distributions of gas and water within the reservoir layers. Additionally, the boundaries of multiphase flow zones are often poorly defined, and the pore volume utilization efficiency (PVUE), which directly impacts effective storage capacity, remains difficult to quantify. These challenges hinder the accurate evaluation of gas storage capacity and complicate the design of optimal construction and operational parameters for UGS facilities. To address these issues, this study proposes an integrated approach combining multi-cycle I/W experiments, numerical reservoir simulations, and the mass balance method to accurately assess UGS storage capacity. The methodology was applied to an active UGS facility constructed in a water-bearing gas reservoir in northwestern China. The gas-bearing reservoir was categorized into four distinct flow zones: the gas zone, the gas-displacing-water zone, the transition zone, and the water zone. Key factors influencing immobile gas-bearing pore volume—such as water invasion and stress sensitivity—were identified for each zone. A mathematical model was developed to predict immobile gas-bearing pore volume, and a quantitative model was established to estimate effective gas storage space (underground) by incorporating PVUE variations across different flow zones. These models provided theoretical foundations for designing UGS construction and operational strategies. The results demonstrated: (1) After six I/W cycles, the measured PVUE in the gas zone was 99.3% and 94.9% for blocks B1 and B2, respectively. In the gas-displacing-water zone, the PVUE was 80.9% and 73.8%, while in the transition zone, it was 47.9% and 40.3%. (2) The total gas-bearing pore volume of the UGS was 9.65 million rm<sup>3</sup> (subsurface conditions), with an effective gas storage space of 5.39 million rm<sup>3</sup> after accounting for PVUE variations across flow zones. (3) Numerical simulations confirmed that the proposed UGS operational design would achieve a total inventory of 8.24 × 10<sup>8</sup> sm<sup>3</sup> (surface conditions) and an effective storage capacity of 6.67 × 10<sup>8</sup> sm<sup>3</sup>. This study provided a robust framework for evaluating and optimizing UGS storage capacity in water-bearing gas reservoirs, offering valuable insights for the design and operation of such facilities.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 717-731"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01Epub Date: 2025-09-26DOI: 10.1016/j.petlm.2025.09.004
Malik Muhammad Ali Awan , Farzain Ud Din Kirmani
CO2 storage is a potential strategy for decarbonizing the fossil-based power and industrial sectors while also serving as a bridge technology for a long-term transition to a zero-emission future. CO2 storage has been identified as the most effective technique for reducing CO2 emissions. While numerous reviews exist, this study offers a critical synthesis focused on the integrated role of petrophysical properties across the entire lifecycle of carbon storage projects—from reservoir characterization and seal integrity assessment to real-time monitoring. Unlike reviews that treat these aspects independently, this paper emphasizes their interdependencies and practical implications for project safety and efficiency. It examines how porosity, permeability, wettability, and other petrophysical parameters influence storage capacity, injectivity, trapping mechanisms, and caprock stability. This review also addresses how uncertainty in petrophysical measurements can propagate through modeling and risk assessments and evaluates tools and simulators in terms of their sensitivity to such inputs. A novel contribution is linking petrophysical data quality with seal failure risks and monitoring reliability, an area underexplored in the existing literature. The study concludes by identifying critical research gaps and proposing a roadmap to enhance the reliability of future CO2 storage projects. These insights aim to support both researchers and project developers in designing more robust, data-informed storage strategies.
{"title":"Reservoir characterization, seal integrity assessment, and monitoring to ensure safe and effective implementation of carbon storage: A critical review","authors":"Malik Muhammad Ali Awan , Farzain Ud Din Kirmani","doi":"10.1016/j.petlm.2025.09.004","DOIUrl":"10.1016/j.petlm.2025.09.004","url":null,"abstract":"<div><div>CO<sub>2</sub> storage is a potential strategy for decarbonizing the fossil-based power and industrial sectors while also serving as a bridge technology for a long-term transition to a zero-emission future. CO<sub>2</sub> storage has been identified as the most effective technique for reducing CO<sub>2</sub> emissions. While numerous reviews exist, this study offers a critical synthesis focused on the integrated role of petrophysical properties across the entire lifecycle of carbon storage projects—from reservoir characterization and seal integrity assessment to real-time monitoring. Unlike reviews that treat these aspects independently, this paper emphasizes their interdependencies and practical implications for project safety and efficiency. It examines how porosity, permeability, wettability, and other petrophysical parameters influence storage capacity, injectivity, trapping mechanisms, and caprock stability. This review also addresses how uncertainty in petrophysical measurements can propagate through modeling and risk assessments and evaluates tools and simulators in terms of their sensitivity to such inputs. A novel contribution is linking petrophysical data quality with seal failure risks and monitoring reliability, an area underexplored in the existing literature. The study concludes by identifying critical research gaps and proposing a roadmap to enhance the reliability of future CO<sub>2</sub> storage projects. These insights aim to support both researchers and project developers in designing more robust, data-informed storage strategies.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 675-698"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01DOI: 10.1016/j.petlm.2025.11.005
Grigoriy Shutov , Viktor Duplyakov , Shadfar Davoodi , Anton Morozov , Dmitriy Popkov , Kirill Pavlenko , Albert Vainshtein , Viktor Kotezhekov , Sergey Kaygorodov , Boris Belozerov , Mars M. Khasanov , Vladimir Vanovskiy , Andrei Osiptsov , Evgeny Burnaev
Obtaining reliable permeability maps of oil reservoirs is crucial for building a robust and accurate reservoir simulation model and, therefore, designing effective recovery strategies. This problem, however, remains challenging, as it requires the integration of various data sources by experts from different disciplines. Moreover, there are no sources to provide direct information about the inter-well space. In this work, a new method based on the data-fusion approach is proposed for predicting two-dimensional permeability maps on the whole reservoir area. This method utilizes non-parametric regression with a custom kernel shape accounting for different data sources: well logs, well tests, and seismics. A convolutional neural network is developed to process seismic data and then incorporate it with other sources. A multi-stage data fusion procedure helps to artificially increase the training dataset for the seismic interpretation model and finally to construct an adequate permeability map. The proposed methodology of permeability map construction from different sources was tested on a real oil reservoir located in Western Siberia. The results demonstrate that the developed map perfectly corresponds to the permeability estimations in the wells, and the inter-well space permeability predictions are considerably improved through the incorporation of the seismic data.
{"title":"A deep learning-aided approach for estimating field permeability map by fusing well logs, well tests, and seismic data","authors":"Grigoriy Shutov , Viktor Duplyakov , Shadfar Davoodi , Anton Morozov , Dmitriy Popkov , Kirill Pavlenko , Albert Vainshtein , Viktor Kotezhekov , Sergey Kaygorodov , Boris Belozerov , Mars M. Khasanov , Vladimir Vanovskiy , Andrei Osiptsov , Evgeny Burnaev","doi":"10.1016/j.petlm.2025.11.005","DOIUrl":"10.1016/j.petlm.2025.11.005","url":null,"abstract":"<div><div>Obtaining reliable permeability maps of oil reservoirs is crucial for building a robust and accurate reservoir simulation model and, therefore, designing effective recovery strategies. This problem, however, remains challenging, as it requires the integration of various data sources by experts from different disciplines. Moreover, there are no sources to provide direct information about the inter-well space. In this work, a new method based on the data-fusion approach is proposed for predicting two-dimensional permeability maps on the whole reservoir area. This method utilizes non-parametric regression with a custom kernel shape accounting for different data sources: well logs, well tests, and seismics. A convolutional neural network is developed to process seismic data and then incorporate it with other sources. A multi-stage data fusion procedure helps to artificially increase the training dataset for the seismic interpretation model and finally to construct an adequate permeability map. The proposed methodology of permeability map construction from different sources was tested on a real oil reservoir located in Western Siberia. The results demonstrate that the developed map perfectly corresponds to the permeability estimations in the wells, and the inter-well space permeability predictions are considerably improved through the incorporation of the seismic data.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 6","pages":"Pages 813-824"},"PeriodicalIF":3.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Enhanced geothermal systems (EGS) are crucial for accessing earth's vast geothermal potential, particularly in low-permeability formations. However, conventional EGS stimulation via hydraulic fracturing often entails high operational costs, substantial water consumption, potential environmental impacts, and risks of induced seismicity. This study presents a novel thermochemical fracturing approach to enhance EGS performance and sustainability while addressing these limitations. The in-situ exothermic reaction of sodium nitrite (NaNO2) and ammonium chloride (NH4Cl) was applied to a 12-inch carbonate rock sample. A specialized core flooding apparatus enabled real-time evaluation of temperature profiles, permeability, and heat transfer enhancements. The thermochemical stimulation increased permeability by 109% (from 19.01 to 39.70 mD) and enhanced heat transfer by 530%. These improvements stem from an extensive micro-fracture network generated by high-pressure nitrogen gas pulses, contrasting with larger planar fractures from hydraulic fracturing. Notably, this was achieved with only a 3.3% increase in porosity, indicating preserved rock integrity. The exothermic reaction prevented core cooling during ambient-temperature stimulation fluid injection, avoiding thermal shock. The thermochemical stimulation primarily generates nitrogen gas (N2) and a brine solution as byproducts. The generated N2 offers the additional benefit of providing well lifting energy, simplifying flowback operations. The novel application of thermochemical stimulation in EGS represents a promising, eco-friendly, and operationally efficient alternative to conventional EGS stimulation techniques.
{"title":"Novel thermochemical fracturing: A breakthrough in sustainable and efficient enhanced geothermal systems (EGS)","authors":"Ahmed Al-Ghamdi , Amjed Hassan , Mohamed Mahmoud , Talal Al-Shafloot","doi":"10.1016/j.petlm.2025.07.004","DOIUrl":"10.1016/j.petlm.2025.07.004","url":null,"abstract":"<div><div>Enhanced geothermal systems (EGS) are crucial for accessing earth's vast geothermal potential, particularly in low-permeability formations. However, conventional EGS stimulation via hydraulic fracturing often entails high operational costs, substantial water consumption, potential environmental impacts, and risks of induced seismicity. This study presents a novel thermochemical fracturing approach to enhance EGS performance and sustainability while addressing these limitations. The in-situ exothermic reaction of sodium nitrite (NaNO<sub>2</sub>) and ammonium chloride (NH<sub>4</sub>Cl) was applied to a 12-inch carbonate rock sample. A specialized core flooding apparatus enabled real-time evaluation of temperature profiles, permeability, and heat transfer enhancements. The thermochemical stimulation increased permeability by 109% (from 19.01 to 39.70 mD) and enhanced heat transfer by 530%. These improvements stem from an extensive micro-fracture network generated by high-pressure nitrogen gas pulses, contrasting with larger planar fractures from hydraulic fracturing. Notably, this was achieved with only a 3.3% increase in porosity, indicating preserved rock integrity. The exothermic reaction prevented core cooling during ambient-temperature stimulation fluid injection, avoiding thermal shock. The thermochemical stimulation primarily generates nitrogen gas (N<sub>2</sub>) and a brine solution as byproducts. The generated N<sub>2</sub> offers the additional benefit of providing well lifting energy, simplifying flowback operations. The novel application of thermochemical stimulation in EGS represents a promising, eco-friendly, and operationally efficient alternative to conventional EGS stimulation techniques.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 5","pages":"Pages 613-623"},"PeriodicalIF":3.5,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advancing the use of natural surfactants in enhanced oil recovery is crucial for sustainable practices in the oil and gas industry. This research assesses the applicability of neem-derived natural surfactants in offshore fields, encompassing surfactant synthesis via saponification, characterization through FT-IR, SEM, and EDS, and measuring surface and interfacial tension across various conditions. Adsorption studies determined the surfactant's adsorption characteristics onto rock, and core flooding tests assessed its efficacy. Surface tension measurements in deionized water (DIW) and brine confirmed the surfactant's surface activity. As the concentration increased from 1 wt% to 6 wt%, the interfacial tension (IFT) significantly decreased from 22.5 mN/m to 7.9 mN/m, marking a 64.8% reduction. Additionally, surfactants formed micelles more efficiently in saline water, with the critical micelle concentration (CMC) dropping from 4.0 wt% in DIW to 0.9 wt%.Adsorption on limestone showed over 50% higher adsorption than sandstone, confirming stronger interactions and higher adsorption saturation. Core flooding experiments demonstrated the surfactant's effectiveness in oil and water-wet conditions. When injected into sandstone, the surfactant achieved a significant additional oil recovery of 24.6% in deionized water, compared to 10.2% in limestone. Conversely, in saline conditions, the surfactant's performance was better in limestone, achieving an additional recovery of 4.9%, whereas in sandstone, it was only 1.6%. This research offers a unique perspective on how natural surfactants perform across different rock types. The findings suggest that neem-derived surfactants hold significant promise for enhancing oil recovery in Kazakhstan's oil fields.
{"title":"Investigation of natural surfactant for oil recovery potential","authors":"Aibike Tukhfatova , Azza Hashim Abbas , Sonny Irawan , Peyman Pourafshary","doi":"10.1016/j.petlm.2025.09.001","DOIUrl":"10.1016/j.petlm.2025.09.001","url":null,"abstract":"<div><div>Advancing the use of natural surfactants in enhanced oil recovery is crucial for sustainable practices in the oil and gas industry. This research assesses the applicability of neem-derived natural surfactants in offshore fields, encompassing surfactant synthesis via saponification, characterization through FT-IR, SEM, and EDS, and measuring surface and interfacial tension across various conditions. Adsorption studies determined the surfactant's adsorption characteristics onto rock, and core flooding tests assessed its efficacy. Surface tension measurements in deionized water (DIW) and brine confirmed the surfactant's surface activity. As the concentration increased from 1 wt% to 6 wt%, the interfacial tension (IFT) significantly decreased from 22.5 mN/m to 7.9 mN/m, marking a 64.8% reduction. Additionally, surfactants formed micelles more efficiently in saline water, with the critical micelle concentration (CMC) dropping from 4.0 wt% in DIW to 0.9 wt%.Adsorption on limestone showed over 50% higher adsorption than sandstone, confirming stronger interactions and higher adsorption saturation. Core flooding experiments demonstrated the surfactant's effectiveness in oil and water-wet conditions. When injected into sandstone, the surfactant achieved a significant additional oil recovery of 24.6% in deionized water, compared to 10.2% in limestone. Conversely, in saline conditions, the surfactant's performance was better in limestone, achieving an additional recovery of 4.9%, whereas in sandstone, it was only 1.6%. This research offers a unique perspective on how natural surfactants perform across different rock types. The findings suggest that neem-derived surfactants hold significant promise for enhancing oil recovery in Kazakhstan's oil fields.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 5","pages":"Pages 638-652"},"PeriodicalIF":3.5,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01Epub Date: 2025-09-04DOI: 10.1016/j.petlm.2025.08.003
Xinsheng Xue , Xiang Chen , Chengxi Huang , Juan Du , Pingli Liu , Yuejun Zhu , Zhengyou Tang
Polymer flooding is a key technology for improving oil recovery in reservoirs with heavy to medium crude oil. However, the adsorption and retention of polymers in reservoir pores can cause reservoir damage. This study investigates the dynamic changes at the wellhead pressure and reservoir damage induced during polymer injection due to adsorption and retention. By integrating continuity equations, polymer flow equilibrium equations, and pore permeability damage equations, a mathematical model is proposed to calculate polymer damage. The model is discretely solved using the finite difference method, effectively simulating the reduction in reservoir porosity and permeability caused by polymer adsorption and retention, as well as the changes in wellhead pressure caused by permeability variations of reservoir and viscosity variations of polymer solutions. Numerical simulation under different injection conditions reveals that the viscosity of polymer solutions is primarily influenced by polymer concentration and Darcy velocity, showing a trend of initial increase followed by decrease radially. The extent of reservoir damage and the rate of increase in wellhead pressure of the injection well correlate positively with polymer concentration and injection volume, with significant reservoir damage concentrated within approximately 2 m around the wellbore. Considering interlayer heterogeneity, inflow is identified as the main factor causing uneven damage distribution. This research enriches the study of damage caused by injection wells and provides a new mathematical model for diagnosing such damage.
{"title":"Numerical simulation study on reservoir damage caused by adsorption and capture retention in polymer injection","authors":"Xinsheng Xue , Xiang Chen , Chengxi Huang , Juan Du , Pingli Liu , Yuejun Zhu , Zhengyou Tang","doi":"10.1016/j.petlm.2025.08.003","DOIUrl":"10.1016/j.petlm.2025.08.003","url":null,"abstract":"<div><div>Polymer flooding is a key technology for improving oil recovery in reservoirs with heavy to medium crude oil. However, the adsorption and retention of polymers in reservoir pores can cause reservoir damage. This study investigates the dynamic changes at the wellhead pressure and reservoir damage induced during polymer injection due to adsorption and retention. By integrating continuity equations, polymer flow equilibrium equations, and pore permeability damage equations, a mathematical model is proposed to calculate polymer damage. The model is discretely solved using the finite difference method, effectively simulating the reduction in reservoir porosity and permeability caused by polymer adsorption and retention, as well as the changes in wellhead pressure caused by permeability variations of reservoir and viscosity variations of polymer solutions. Numerical simulation under different injection conditions reveals that the viscosity of polymer solutions is primarily influenced by polymer concentration and Darcy velocity, showing a trend of initial increase followed by decrease radially. The extent of reservoir damage and the rate of increase in wellhead pressure of the injection well correlate positively with polymer concentration and injection volume, with significant reservoir damage concentrated within approximately 2 m around the wellbore. Considering interlayer heterogeneity, inflow is identified as the main factor causing uneven damage distribution. This research enriches the study of damage caused by injection wells and provides a new mathematical model for diagnosing such damage.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 5","pages":"Pages 624-637"},"PeriodicalIF":3.5,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To solve the problem whereby an oil reservoir with applicable boundaries of the current sand-inhibiting and water-control agent is unclear, a supramolecular sand-inhibiting and water-control agent PDKM was prepared using acrylamide (AM), methacryloxyethyltrimethyl ammonium chloride (DMC), styrene (SM), and γ-methacryloyloxypropyltrimethoxysilane (KH570) as comonomers. The molecular structure of PDKM was verified by 1H-NMR and FT-IR. On the basis of establishing an evaluation method that can screen the performance of sand-inhibiting agent at a flow rate of 100 mL/min, the oil reservoir applicable boundaries of PDKM were obtained through the evaluation of sand-inhibiting and water-control performance. The experimental results show that when the concentration of PDKM is 5000 mg/L, the oil reservoir conditions are temperature ≤90 °C, formation water salinity ≤21,249 mg/L, the degree of sand production corresponding to slight sand production and particle migration, crude oil viscosity ≤50 mPa·s, primary water flooding water cut ≥75%, and formation permeability contrast ≤2. The performance with respect to sand inhibiting and water control can all reach an excellent level. Therefore, the PDKM solves the problem whereby the applicability of the current sand-inhibiting and water-control agent is unclear, and provides direction for the selection of suitable products in the oilfield production site.
{"title":"Preparation of a supramolecular sand-inhibiting and water-control agent and study of its applicability to oil reservoirs","authors":"Tianmeng Lei , Yefei Wang , Mingchen Ding , Wuhua Chen , Zhenye Yu , Zhixue Huang , Motorova Kseniya Alexandrovna","doi":"10.1016/j.petlm.2025.09.003","DOIUrl":"10.1016/j.petlm.2025.09.003","url":null,"abstract":"<div><div>To solve the problem whereby an oil reservoir with applicable boundaries of the current sand-inhibiting and water-control agent is unclear, a supramolecular sand-inhibiting and water-control agent PDKM was prepared using acrylamide (AM), methacryloxyethyltrimethyl ammonium chloride (DMC), styrene (SM), and γ-methacryloyloxypropyltrimethoxysilane (KH570) as comonomers. The molecular structure of PDKM was verified by <sup>1</sup>H-NMR and FT-IR. On the basis of establishing an evaluation method that can screen the performance of sand-inhibiting agent at a flow rate of 100 mL/min, the oil reservoir applicable boundaries of PDKM were obtained through the evaluation of sand-inhibiting and water-control performance. The experimental results show that when the concentration of PDKM is 5000 mg/L, the oil reservoir conditions are temperature ≤90 °C, formation water salinity ≤21,249 mg/L, the degree of sand production corresponding to slight sand production and particle migration, crude oil viscosity ≤50 mPa·s, primary water flooding water cut ≥75%, and formation permeability contrast ≤2. The performance with respect to sand inhibiting and water control can all reach an excellent level. Therefore, the PDKM solves the problem whereby the applicability of the current sand-inhibiting and water-control agent is unclear, and provides direction for the selection of suitable products in the oilfield production site.</div></div>","PeriodicalId":37433,"journal":{"name":"Petroleum","volume":"11 5","pages":"Pages 653-661"},"PeriodicalIF":3.5,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}