Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60013-9
Yuhan WANG , Zhengdong LEI , Yishan LIU , Xiuxiu PAN , Zhewei CHEN , Yuanqing ZHANG , Xiaoyu ZHENG , Pengcheng LIU , Yi HAN
Considering the interactions between fluid molecules and pore walls, variations in critical properties, capillary forces, and the influence of the adsorbed phase, this study investigates the phase behavior of the CO2-shale oil within nanopores by utilizing a modified Peng-Robinson (PR) equation of state alongside a three-phase (gas-liquid-adsorbed) equilibrium calculation method. The results reveal that nano-confinement effects of the pores lead to a decrease in both critical temperature and critical pressure of fluids as pore size diminishes. Specifically, CO2 acts to inhibit the reduction of the critical temperature of the system while promoting the decrease in critical pressure. Furthermore, an increase in the mole fraction of CO2 causes the critical point of the system to shift leftward and reduces the area of the phase envelope. In the shale reservoirs of Block A in Gulong of the Daqing Oilfield, China, pronounced confinement effects are observed. At a pore diameter of 10 nm, reservoir fluids progressively exhibit characteristics typical of condensate gas reservoirs. Notably, the CO2 content in liquid in 10 nm pores increases by 20.0% compared to that in 100 nm pores, while the CO2 content in gas decreases by 10.8%. These findings indicate that confinement effects enhance CO2 mass transfer within nanopores, thereby facilitating CO2 sequestration and improving microscopic oil recovery.
{"title":"Phase behavior of CO2-shale oil in nanopores","authors":"Yuhan WANG , Zhengdong LEI , Yishan LIU , Xiuxiu PAN , Zhewei CHEN , Yuanqing ZHANG , Xiaoyu ZHENG , Pengcheng LIU , Yi HAN","doi":"10.1016/S1876-3804(25)60013-9","DOIUrl":"10.1016/S1876-3804(25)60013-9","url":null,"abstract":"<div><div>Considering the interactions between fluid molecules and pore walls, variations in critical properties, capillary forces, and the influence of the adsorbed phase, this study investigates the phase behavior of the CO<sub>2</sub>-shale oil within nanopores by utilizing a modified Peng-Robinson (PR) equation of state alongside a three-phase (gas-liquid-adsorbed) equilibrium calculation method. The results reveal that nano-confinement effects of the pores lead to a decrease in both critical temperature and critical pressure of fluids as pore size diminishes. Specifically, CO<sub>2</sub> acts to inhibit the reduction of the critical temperature of the system while promoting the decrease in critical pressure. Furthermore, an increase in the mole fraction of CO<sub>2</sub> causes the critical point of the system to shift leftward and reduces the area of the phase envelope. In the shale reservoirs of Block A in Gulong of the Daqing Oilfield, China, pronounced confinement effects are observed. At a pore diameter of 10 nm, reservoir fluids progressively exhibit characteristics typical of condensate gas reservoirs. Notably, the CO<sub>2</sub> content in liquid in 10 nm pores increases by 20.0% compared to that in 100 nm pores, while the CO<sub>2</sub> content in gas decreases by 10.8%. These findings indicate that confinement effects enhance CO<sub>2</sub> mass transfer within nanopores, thereby facilitating CO<sub>2</sub> sequestration and improving microscopic oil recovery.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 182-195"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60006-1
Qinghua WANG , Haijun YANG , Wei YANG
Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression, Tarim Basin, over recent years. A new round of comprehensive geological research has formed four new understandings: (1) Establish structural model consisting of multi-detachment composite, multi-stage structural superposition and multi-layer deformation. Multi-stage structural traps are overlapped vertically, and a series of structural traps are discovered in underlying ultra-deep layers. (2) Five sets of high-quality large-scale source rocks of three types of organic phases are developed in the Triassic and Jurassic systems, and forming a good combination of source-reservoir-cap rocks in ultra-deep layers with three sets of large-scale regional reservoir and cap rocks. (3) The formation of large oil and gas fields is controlled by four factors which are source, reservoir, cap rocks and fault. Based on the spatial configuration relationship of these four factors, a new three-dimensional reservoir formation model for ultra-deep clastic rocks in the Kuqa Depression has been established. (4) The next key exploration fields for ultra-deep clastic rocks in the Kuqa Depression include conventional and unconventional oil and gas. The conventional oil and gas fields include the deep multi-layer oil-gas accumulation zone in Kelasu, tight sandstone gas of Jurassic Ahe Formation in the northern structural zone, multi-target layer lithological oil and gas reservoirs in Zhongqiu–Dina structural zone, lithologic-stratigraphic and buried hill composite reservoirs in south slope and other favorable areas. Unconventional oil and gas fields include deep coal rock gas of Jurassic Kezilenuer and Yangxia formations, Triassic Tariqike Formation and Middle-Lower Jurassic and Upper Triassic continental shale gas. The achievements have important reference significance for enriching the theory of ultra-deep clastic rock oil and gas exploration and guiding the future oil and gas exploration deployment.
{"title":"New progress and future exploration targets in petroleum geological research of ultra-deep clastic rocks in Kuqa Depression, Tarim Basin, NW China","authors":"Qinghua WANG , Haijun YANG , Wei YANG","doi":"10.1016/S1876-3804(25)60006-1","DOIUrl":"10.1016/S1876-3804(25)60006-1","url":null,"abstract":"<div><div>Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression, Tarim Basin, over recent years. A new round of comprehensive geological research has formed four new understandings: (1) Establish structural model consisting of multi-detachment composite, multi-stage structural superposition and multi-layer deformation. Multi-stage structural traps are overlapped vertically, and a series of structural traps are discovered in underlying ultra-deep layers. (2) Five sets of high-quality large-scale source rocks of three types of organic phases are developed in the Triassic and Jurassic systems, and forming a good combination of source-reservoir-cap rocks in ultra-deep layers with three sets of large-scale regional reservoir and cap rocks. (3) The formation of large oil and gas fields is controlled by four factors which are source, reservoir, cap rocks and fault. Based on the spatial configuration relationship of these four factors, a new three-dimensional reservoir formation model for ultra-deep clastic rocks in the Kuqa Depression has been established. (4) The next key exploration fields for ultra-deep clastic rocks in the Kuqa Depression include conventional and unconventional oil and gas. The conventional oil and gas fields include the deep multi-layer oil-gas accumulation zone in Kelasu, tight sandstone gas of Jurassic Ahe Formation in the northern structural zone, multi-target layer lithological oil and gas reservoirs in Zhongqiu–Dina structural zone, lithologic-stratigraphic and buried hill composite reservoirs in south slope and other favorable areas. Unconventional oil and gas fields include deep coal rock gas of Jurassic Kezilenuer and Yangxia formations, Triassic Tariqike Formation and Middle-Lower Jurassic and Upper Triassic continental shale gas. The achievements have important reference significance for enriching the theory of ultra-deep clastic rock oil and gas exploration and guiding the future oil and gas exploration deployment.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 79-94"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60019-X
Bo XIONG , Hao XU , Chaohe FANG , Shixiang LI , Shuling TANG , Shejiao WANG , Jingjie WU , Xuejing SONG , Lu ZHANG , Jinwei WANG , Xiangquan WEI , Fudong XIN , Boning TANG , Yin LONG
China has abundant resources of hot dry rocks. However, due to the fact that the evaluation methods for favorable areas are mainly qualitative, and the evaluation indicators and standards are inconsistent, which restrict the evaluation efficiency and exploration process of dry hot rocks. This paper is based on the understanding of the geologic features and genesis mechanisms of hot dry rocks in China and abroad. By integrating the main controlling factors of hot dry rock formation, and using index grading and quantification, the fuzzy hierarchical comprehensive method is applied to establish an evaluation system and standards for favorable areas of hot dry rocks. The evaluation system is based on four indicators: heat source, thermal channel, thermal reservoir and cap rock. It includes 11 evaluation parameters, including time of magmatic/volcanic activity, depth of molten mass or magma chamber, distribution of discordogenic faults, burial depth of thermal reservoir, cap rock type and thickness, surface thermal anomaly, heat flow, geothermal gradient, Moho depth, Curie depth, Earthquake magnitude and focal depth. Each parameter is divided into 3 levels. Applying this evaluation system to assess hot dry rock in central Inner Mongolia revealed that Class I favorable zones cover approximately 494 km2, while Class II favorable zones span about 5.7×104 km2. The Jirgalangtu Sag and Honghaershute Sag in the Erlian Basin, along with Reshuitang Town in Keshiketeng Banner, Reshui Town in Ningcheng County, and Reshuitang Town in Aohan Banner of Chifeng City, are identified as Class I favorable zones for hot dry rock resources. These areas are characterized by high-temperature subsurface molten bodies or magma chambers serving as high-quality heat sources, shallow thermal reservoir depths, and overlying thick sedimentary rock layers acting as caprock. The establishment and application of the evaluation system for favorable areas of hot dry rock are expected to provide new approaches and scientific basis for guiding the practice of selecting hot dry rock areas in China.
{"title":"Construction and application of favorable target evaluation system for hot dry rock","authors":"Bo XIONG , Hao XU , Chaohe FANG , Shixiang LI , Shuling TANG , Shejiao WANG , Jingjie WU , Xuejing SONG , Lu ZHANG , Jinwei WANG , Xiangquan WEI , Fudong XIN , Boning TANG , Yin LONG","doi":"10.1016/S1876-3804(25)60019-X","DOIUrl":"10.1016/S1876-3804(25)60019-X","url":null,"abstract":"<div><div>China has abundant resources of hot dry rocks. However, due to the fact that the evaluation methods for favorable areas are mainly qualitative, and the evaluation indicators and standards are inconsistent, which restrict the evaluation efficiency and exploration process of dry hot rocks. This paper is based on the understanding of the geologic features and genesis mechanisms of hot dry rocks in China and abroad. By integrating the main controlling factors of hot dry rock formation, and using index grading and quantification, the fuzzy hierarchical comprehensive method is applied to establish an evaluation system and standards for favorable areas of hot dry rocks. The evaluation system is based on four indicators: heat source, thermal channel, thermal reservoir and cap rock. It includes 11 evaluation parameters, including time of magmatic/volcanic activity, depth of molten mass or magma chamber, distribution of discordogenic faults, burial depth of thermal reservoir, cap rock type and thickness, surface thermal anomaly, heat flow, geothermal gradient, Moho depth, Curie depth, Earthquake magnitude and focal depth. Each parameter is divided into 3 levels. Applying this evaluation system to assess hot dry rock in central Inner Mongolia revealed that Class I favorable zones cover approximately 494 km<sup>2</sup>, while Class II favorable zones span about 5.7×10<sup>4</sup> km<sup>2</sup>. The Jirgalangtu Sag and Honghaershute Sag in the Erlian Basin, along with Reshuitang Town in Keshiketeng Banner, Reshui Town in Ningcheng County, and Reshuitang Town in Aohan Banner of Chifeng City, are identified as Class I favorable zones for hot dry rock resources. These areas are characterized by high-temperature subsurface molten bodies or magma chambers serving as high-quality heat sources, shallow thermal reservoir depths, and overlying thick sedimentary rock layers acting as caprock. The establishment and application of the evaluation system for favorable areas of hot dry rock are expected to provide new approaches and scientific basis for guiding the practice of selecting hot dry rock areas in China.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 258-271"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60014-0
Xiliang LIU , Hao CHEN , Yang LI , Yangwen ZHU , Haiying LIAO , Qingmin ZHAO , Xianmin ZHOU , Hongbo ZENG
Using the ultra-low permeability reservoirs in the L block of the Jiangsu oilfield as an example, a series of experiments, including slim tube displacement experiments of CO2-oil system, injection capacity experiments, and high-temperature, high-pressure online nuclear magnetic resonance (NMR) displacement experiments, are conducted to reveal the oil/gas mass transfer pattern and oil production mechanisms during CO2 flooding in ultra-low permeability reservoirs. The impacts of CO2 storage pore range and miscibility on oil production and CO2 storage characteristics during CO2 flooding are clarified. The CO2 flooding process is divided into three stages: oil displacement stage by CO2, CO2 breakthrough stage, CO2 extraction stage. Crude oil expansion and viscosity reduction are the main mechanisms for improving recovery in the CO2 displacement stage. After CO2 breakthrough, the extraction of light components from the crude oil further enhances oil recovery. During CO2 flooding, the contribution of crude oil in large pores to the enhanced recovery exceeds 46%, while crude oil in medium pores serves as a reserve for incremental recovery. After CO2 breakthrough, a small portion of the crude oil is extracted and carried into nano-scale pores by CO2, becoming residual oil that is hard to recover. As the miscibility increases, the CO2 front moves more stably and sweeps a larger area, leading to increased CO2 storage range and volume. The CO2 full-storage stage contributes the most to the overall CO2 storage volume. In the CO2 escape stage, the storage mechanism involves partial in-situ storage of crude oil within the initial pore range and the CO2 carrying crude oil into smaller pores to increase the volume of stored CO2. In the CO2 leakage stage, as crude oil is produced, a significant amount of CO2 leaks out, causing a sharp decline in the storage efficiency.
{"title":"Oil production characteristics and CO2 storage mechanisms of CO2 flooding in ultra-low permeability sandstone oil reservoirs","authors":"Xiliang LIU , Hao CHEN , Yang LI , Yangwen ZHU , Haiying LIAO , Qingmin ZHAO , Xianmin ZHOU , Hongbo ZENG","doi":"10.1016/S1876-3804(25)60014-0","DOIUrl":"10.1016/S1876-3804(25)60014-0","url":null,"abstract":"<div><div>Using the ultra-low permeability reservoirs in the L block of the Jiangsu oilfield as an example, a series of experiments, including slim tube displacement experiments of CO<sub>2</sub>-oil system, injection capacity experiments, and high-temperature, high-pressure online nuclear magnetic resonance (NMR) displacement experiments, are conducted to reveal the oil/gas mass transfer pattern and oil production mechanisms during CO<sub>2</sub> flooding in ultra-low permeability reservoirs. The impacts of CO<sub>2</sub> storage pore range and miscibility on oil production and CO<sub>2</sub> storage characteristics during CO<sub>2</sub> flooding are clarified. The CO<sub>2</sub> flooding process is divided into three stages: oil displacement stage by CO<sub>2</sub>, CO<sub>2</sub> breakthrough stage, CO<sub>2</sub> extraction stage. Crude oil expansion and viscosity reduction are the main mechanisms for improving recovery in the CO<sub>2</sub> displacement stage. After CO<sub>2</sub> breakthrough, the extraction of light components from the crude oil further enhances oil recovery. During CO<sub>2</sub> flooding, the contribution of crude oil in large pores to the enhanced recovery exceeds 46%, while crude oil in medium pores serves as a reserve for incremental recovery. After CO<sub>2</sub> breakthrough, a small portion of the crude oil is extracted and carried into nano-scale pores by CO<sub>2</sub>, becoming residual oil that is hard to recover. As the miscibility increases, the CO<sub>2</sub> front moves more stably and sweeps a larger area, leading to increased CO<sub>2</sub> storage range and volume. The CO<sub>2</sub> full-storage stage contributes the most to the overall CO<sub>2</sub> storage volume. In the CO<sub>2</sub> escape stage, the storage mechanism involves partial in-situ storage of crude oil within the initial pore range and the CO<sub>2</sub> carrying crude oil into smaller pores to increase the volume of stored CO<sub>2</sub>. In the CO<sub>2</sub> leakage stage, as crude oil is produced, a significant amount of CO<sub>2</sub> leaks out, causing a sharp decline in the storage efficiency.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 196-207"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60018-8
Jianhua QIN , Chenggang XIAN , Jing ZHANG , Tianbo LIANG , Wenzhong WANG , Siyuan LI , Jinning ZHANG , Yang ZHANG , Fujian ZHOU
In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing, a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation (T1b2 and T1b3) in Ma-131 well area, which learned from the successful experience of hydraulic fracturing test sites in North America (HFTS-1). Twelve horizontal wells and a high-angle coring well MaJ02 were drilled. The orientation, connection, propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans, imaging logs, direct observation of cores from Well MaJ02, and combined with tracer monitoring data. Results indicate that: (1) Two types of fractures have developed by hydraulic fracturing, i.e. tensile fractures and shear fractures. Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress, and propagate less than 50 m from perforation clusters. Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures, and some of them are in conjugated pairs. Overall, tensile fractures alternate with shear fractures, with shear fractures dominated and activated after tensile ones. (2) Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production, and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed. (3) Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters, which is smaller in the mudstone than the conglomerate. Larger fracturing scale and smaller cluster spacing lead to a higher fracture density, which are important directions to improve the well productivity.
{"title":"Characteristics of hydraulic fracture network in the tight conglomerate reservoir based on a hydraulic fracturing test site","authors":"Jianhua QIN , Chenggang XIAN , Jing ZHANG , Tianbo LIANG , Wenzhong WANG , Siyuan LI , Jinning ZHANG , Yang ZHANG , Fujian ZHOU","doi":"10.1016/S1876-3804(25)60018-8","DOIUrl":"10.1016/S1876-3804(25)60018-8","url":null,"abstract":"<div><div>In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing, a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation (T<sub>1</sub>b<sub>2</sub> and T<sub>1</sub>b<sub>3</sub>) in Ma-131 well area, which learned from the successful experience of hydraulic fracturing test sites in North America (HFTS-1). Twelve horizontal wells and a high-angle coring well MaJ02 were drilled. The orientation, connection, propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans, imaging logs, direct observation of cores from Well MaJ02, and combined with tracer monitoring data. Results indicate that: (1) Two types of fractures have developed by hydraulic fracturing, i.e. tensile fractures and shear fractures. Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress, and propagate less than 50 m from perforation clusters. Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures, and some of them are in conjugated pairs. Overall, tensile fractures alternate with shear fractures, with shear fractures dominated and activated after tensile ones. (2) Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production, and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed. (3) Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters, which is smaller in the mudstone than the conglomerate. Larger fracturing scale and smaller cluster spacing lead to a higher fracture density, which are important directions to improve the well productivity.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 245-257"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates the macroscopic and microscopic characteristics of viscosity reduction and quality improvement of heavy oil in a supercritical water environment through laboratory experiments and testing. The effect of three reaction parameters, i.e. reaction temperature, reaction time and oil-water ratio, is analyzed on the product and their correlation with viscosity. The results show that the flow state of heavy oil is significantly improved with a viscosity reduction of 99.4% in average after the reaction in the supercritical water. Excessively high reaction temperature leads to a higher content of resins and asphaltenes, with significantly increasing production of coke. The optimal temperature ranges in 380–420 °C. Prolonged reaction time could continuously increase the yield of light oil, but it will also results in the growth of resins and asphaltenes, with the optimal reaction time of 150 min. Reducing the oil-water ratio helps improve the diffusion environment within the reaction system and reduce the content of resins and asphaltenes, but it will increase the cost of heavy oil treatment. An oil-water ratio of 1︰2 is considered as optimum to balance the quality improvement, viscosity reduction and reaction economics. The correlation of the three reaction parameters relative to the oil sample viscosity is ranked as temperature, time and oil-water ratio. Among the four fractions of heavy oil, the viscosity is dominated by asphaltene content, followed by aromatic content and less affected by resins and saturates contents.
{"title":"Experiments on the characteristics of upgrading and viscosity reduction of heavy oil under supercritical water conditions","authors":"Zhongwei HUANG, Yazhou SHEN, Xiaoguang WU, Gensheng LI, Tengda LONG, Wenchao ZOU, Weizhen SUN, Haoyang SHEN","doi":"10.1016/S1876-3804(25)60012-7","DOIUrl":"10.1016/S1876-3804(25)60012-7","url":null,"abstract":"<div><div>This paper investigates the macroscopic and microscopic characteristics of viscosity reduction and quality improvement of heavy oil in a supercritical water environment through laboratory experiments and testing. The effect of three reaction parameters, i.e. reaction temperature, reaction time and oil-water ratio, is analyzed on the product and their correlation with viscosity. The results show that the flow state of heavy oil is significantly improved with a viscosity reduction of 99.4% in average after the reaction in the supercritical water. Excessively high reaction temperature leads to a higher content of resins and asphaltenes, with significantly increasing production of coke. The optimal temperature ranges in 380–420 °C. Prolonged reaction time could continuously increase the yield of light oil, but it will also results in the growth of resins and asphaltenes, with the optimal reaction time of 150 min. Reducing the oil-water ratio helps improve the diffusion environment within the reaction system and reduce the content of resins and asphaltenes, but it will increase the cost of heavy oil treatment. An oil-water ratio of 1︰2 is considered as optimum to balance the quality improvement, viscosity reduction and reaction economics. The correlation of the three reaction parameters relative to the oil sample viscosity is ranked as temperature, time and oil-water ratio. Among the four fractions of heavy oil, the viscosity is dominated by asphaltene content, followed by aromatic content and less affected by resins and saturates contents.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 170-181"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60001-2
Wenzhi ZHAO , Wei LIU , Congsheng BIAN , Xianyang LIU , Xiugang PU , Jiamin LU , Yongxin LI , Junhui LI , Shiju LIU , Ming GUAN , Xiuli FU , Jin DONG
In addition to the organic matter type, abundance, thermal maturity, and shale reservoir space, the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons in source rocks of lacustrine shale, yet this aspect has received little attention. This paper, based on the case analysis, explores how preservation conditions influence the enrichment of mobile hydrocarbons in shale oil. Research showns that good preservation conditions play three key roles. (1) Ensure the retention of sufficient light hydrocarbons (C1–C13), medium hydrocarbons (C14–C25) and small molecular aromatics (including 1–2 benzene rings) in the formation, which enhances the fluidity and flow of shale oil; (2) Maintain a high energy field (abnormally high pressure), thus facilitating the maximum outflow of shale oil; (3) Ensure that the retained hydrocarbons have the miscible flow condition of multi-component hydrocarbons (light hydrocarbons, medium hydrocarbons, heavy hydrocarbons, and heteroatomic compounds), so that the heavy hydrocarbons (ΣC25+) and heavy components (non-hydrocarbons and asphaltenes) have improved fluidity and maximum flow capacity. In conclusion, in addition to the advantages of organic matter type, abundance, thermal maturity, and reservoir space, good preservation conditions of shale layers are essential for the formation of economically viable shale oil reservoirs, which should be incorporated into the evaluation criteria of shale oil-rich areas/segments and considered a necessary factor when selecting favorable exploration targets.
{"title":"Role of preservation conditions on enrichment and fluidity maintenance of medium to high maturity lacustrine shale oil","authors":"Wenzhi ZHAO , Wei LIU , Congsheng BIAN , Xianyang LIU , Xiugang PU , Jiamin LU , Yongxin LI , Junhui LI , Shiju LIU , Ming GUAN , Xiuli FU , Jin DONG","doi":"10.1016/S1876-3804(25)60001-2","DOIUrl":"10.1016/S1876-3804(25)60001-2","url":null,"abstract":"<div><div>In addition to the organic matter type, abundance, thermal maturity, and shale reservoir space, the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons in source rocks of lacustrine shale, yet this aspect has received little attention. This paper, based on the case analysis, explores how preservation conditions influence the enrichment of mobile hydrocarbons in shale oil. Research showns that good preservation conditions play three key roles. (1) Ensure the retention of sufficient light hydrocarbons (C<sub>1</sub>–C<sub>13</sub>), medium hydrocarbons (C<sub>14</sub>–C<sub>25</sub>) and small molecular aromatics (including 1–2 benzene rings) in the formation, which enhances the fluidity and flow of shale oil; (2) Maintain a high energy field (abnormally high pressure), thus facilitating the maximum outflow of shale oil; (3) Ensure that the retained hydrocarbons have the miscible flow condition of multi-component hydrocarbons (light hydrocarbons, medium hydrocarbons, heavy hydrocarbons, and heteroatomic compounds), so that the heavy hydrocarbons (ΣC<sub>25+</sub>) and heavy components (non-hydrocarbons and asphaltenes) have improved fluidity and maximum flow capacity. In conclusion, in addition to the advantages of organic matter type, abundance, thermal maturity, and reservoir space, good preservation conditions of shale layers are essential for the formation of economically viable shale oil reservoirs, which should be incorporated into the evaluation criteria of shale oil-rich areas/segments and considered a necessary factor when selecting favorable exploration targets.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 1-16"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60008-5
Yong TANG , Chengzao JIA , Fangwen CHEN , Wenjun HE , Dongming ZHI , Xiang SHAN , Xincai YOU , Lin JIANG , Yang ZOU , Tao WU , An XIE
Based on the experimental results of casting thin section, low temperature nitrogen adsorption, high pressure mercury injection, nuclear magnetic resonance T2 spectrum, contact angle and oil-water interfacial tension, the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag, Junggar Basin, are revealed. (1) With the decrease of reservoir particle size, the volume of pores connected by large throats and the volume of large pores show a decreasing trend, and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner. The upper limits of throat radius, porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7 µm, 8% and 0.1×10−3 μm2, respectively. (2) As the reservoir particle size decreases, the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner. With the increase of driving pressure, the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing, respectively. (3) With the increase of throat radius, the driving pressure of reservoir with different particle levels presents three stages, namely rapid decrease, slow decrease and stabilization. The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius. According to the above experimental analysis, it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.
{"title":"Relationship between pore throat structure and crude oil mobility of full particle sequence reservoirs in Permian Fengcheng Formation, Mahu Sag, Junggar Basin, NW China","authors":"Yong TANG , Chengzao JIA , Fangwen CHEN , Wenjun HE , Dongming ZHI , Xiang SHAN , Xincai YOU , Lin JIANG , Yang ZOU , Tao WU , An XIE","doi":"10.1016/S1876-3804(25)60008-5","DOIUrl":"10.1016/S1876-3804(25)60008-5","url":null,"abstract":"<div><div>Based on the experimental results of casting thin section, low temperature nitrogen adsorption, high pressure mercury injection, nuclear magnetic resonance <em>T</em><sub>2</sub> spectrum, contact angle and oil-water interfacial tension, the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag, Junggar Basin, are revealed. (1) With the decrease of reservoir particle size, the volume of pores connected by large throats and the volume of large pores show a decreasing trend, and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner. The upper limits of throat radius, porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7 µm, 8% and 0.1×10<sup>−3</sup> μm<sup>2</sup>, respectively. (2) As the reservoir particle size decreases, the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner. With the increase of driving pressure, the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing, respectively. (3) With the increase of throat radius, the driving pressure of reservoir with different particle levels presents three stages, namely rapid decrease, slow decrease and stabilization. The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius. According to the above experimental analysis, it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 112-124"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60017-6
Qinghai YANG , Chenglong LIAO , Deli JIA , Yingjun ZHU , Chuan YU , Lingwei KONG , Yang YU , Kai DU
To address the challenges associated with existing separated zone oil production technologies, such as incompatibility with pump inspection operations, short effective working life, and poor communication reliability, an innovative electromagnetic coupling intelligent zonal oil production technology has been proposed. The core and accessory tools have been developed and applied in field tests. This technology employs a pipe string structure incorporation a release sub, which separates the production and allocation pipe strings. When the two strings are docked downhole, electromagnetic coupling enables close-range wireless transmission of electrical power and signals between the strings, powering multiple downhole intelligent production allocators (IPAs) and enabling two-way communication. Core tools adapted to the complex working conditions downhole were developed, including downhole electricity & signal transmission equipment based on electromagnetic coupling (EST), IPAs, and ground communication controllers (GCCs). Accessory tools, including large-diameter release sub anchor and cable-crossing packers, have also been technically finalized. Field tests conducted on ten wells in Daqing Oilfield demonstrated that the downhole docking of the two strings was convenient and reliable, and the EST worked stably. Real-time monitoring of flow rate, pressure and temperature in separate layers and regulation of zonal fluid production were also achieved. This technology has enhanced reservoir understanding and achieved practical production results of increased oil output with reduced water cut.
{"title":"An intelligent separated zone oil production technology based on electromagnetic coupling principle","authors":"Qinghai YANG , Chenglong LIAO , Deli JIA , Yingjun ZHU , Chuan YU , Lingwei KONG , Yang YU , Kai DU","doi":"10.1016/S1876-3804(25)60017-6","DOIUrl":"10.1016/S1876-3804(25)60017-6","url":null,"abstract":"<div><div>To address the challenges associated with existing separated zone oil production technologies, such as incompatibility with pump inspection operations, short effective working life, and poor communication reliability, an innovative electromagnetic coupling intelligent zonal oil production technology has been proposed. The core and accessory tools have been developed and applied in field tests. This technology employs a pipe string structure incorporation a release sub, which separates the production and allocation pipe strings. When the two strings are docked downhole, electromagnetic coupling enables close-range wireless transmission of electrical power and signals between the strings, powering multiple downhole intelligent production allocators (IPAs) and enabling two-way communication. Core tools adapted to the complex working conditions downhole were developed, including downhole electricity & signal transmission equipment based on electromagnetic coupling (EST), IPAs, and ground communication controllers (GCCs). Accessory tools, including large-diameter release sub anchor and cable-crossing packers, have also been technically finalized. Field tests conducted on ten wells in Daqing Oilfield demonstrated that the downhole docking of the two strings was convenient and reliable, and the EST worked stably. Real-time monitoring of flow rate, pressure and temperature in separate layers and regulation of zonal fluid production were also achieved. This technology has enhanced reservoir understanding and achieved practical production results of increased oil output with reduced water cut.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 230-244"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/S1876-3804(25)60009-7
Xiucheng TAN , Ruyi HE , Wenjie YANG , Bing LUO , Jiangbo SHI , Lianjin ZHANG , Minglong LI , Yuxin TANG , Di XIAO , Zhanfeng QIAO
This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation (lower Mao 2 Member) in the Wusheng—Tongnan area of the Sichuan Basin, SW China, through comprehensive analysis of geological, geophysical and geochemical data. The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone, which have typical karst characteristics of early diagenetic stage. The dolomites at the edge of the karst system and in the fillings have dissolved estuaries, and the dolomite breccia has micrite envelope and rim cement at the edge, indicating that dolomitization is earlier than the early diagenetic karstification. The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater. The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage, which are locally reformed by fractures and hydrothermal processes. The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence, and mainly occurs in the late highstand of the fourth-order cycle. Moreover, the size of dolomite is closely related to formation thickness, and it is concentrated in the formation thickness conversion area, followed by the thinner area. According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle, it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes, and the reservoir-forming model with shoal, dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established. On this basis, the paleogeomorphology in the lower Mao 2 Member is restored using well-seismic data, and the reservoir distribution is predicted. The prediction results have been verified by the latest results of exploration wells and tests, which provide an important reference for the prediction of thin dolomite reservoirs under similar geological setting.
{"title":"Origin and distribution model of thin dolomite reservoirs in the lower sub-member of Mao 2 Member of Middle Permian Maokou Formation in Wusheng-Tongnan area, Sichuan Basin, SW China","authors":"Xiucheng TAN , Ruyi HE , Wenjie YANG , Bing LUO , Jiangbo SHI , Lianjin ZHANG , Minglong LI , Yuxin TANG , Di XIAO , Zhanfeng QIAO","doi":"10.1016/S1876-3804(25)60009-7","DOIUrl":"10.1016/S1876-3804(25)60009-7","url":null,"abstract":"<div><div>This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation (lower Mao 2 Member) in the Wusheng—Tongnan area of the Sichuan Basin, SW China, through comprehensive analysis of geological, geophysical and geochemical data. The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone, which have typical karst characteristics of early diagenetic stage. The dolomites at the edge of the karst system and in the fillings have dissolved estuaries, and the dolomite breccia has micrite envelope and rim cement at the edge, indicating that dolomitization is earlier than the early diagenetic karstification. The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater. The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage, which are locally reformed by fractures and hydrothermal processes. The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence, and mainly occurs in the late highstand of the fourth-order cycle. Moreover, the size of dolomite is closely related to formation thickness, and it is concentrated in the formation thickness conversion area, followed by the thinner area. According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle, it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes, and the reservoir-forming model with shoal, dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established. On this basis, the paleogeomorphology in the lower Mao 2 Member is restored using well-seismic data, and the reservoir distribution is predicted. The prediction results have been verified by the latest results of exploration wells and tests, which provide an important reference for the prediction of thin dolomite reservoirs under similar geological setting.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 125-142"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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