A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores
Nuclear magnetic resonance (NMR) and high-pressure mercury injection (HPMI) have been widely used as common characterization methods of pore-throat. It is generally believed that there is a power function relationship between transverse relaxation time (T<sub>2</sub>) and pore-throat rad...
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2025-01-01
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| author | Yanchun Su Chunhua Zhao Xianjie Li Xiujun Wang Jian Zhang Bo Huang Xiaofeng Tian Mingxi Liu Kaoping Song |
| author_facet | Yanchun Su Chunhua Zhao Xianjie Li Xiujun Wang Jian Zhang Bo Huang Xiaofeng Tian Mingxi Liu Kaoping Song |
| author_sort | Yanchun Su |
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| description | Nuclear magnetic resonance (NMR) and high-pressure mercury injection (HPMI) have been widely used as common characterization methods of pore-throat. It is generally believed that there is a power function relationship between transverse relaxation time (T<sub>2</sub>) and pore-throat radius (r), but the segmentation process of the pore-throat interval is subjective, which affects the conversion accuracy. In this paper, ordered clustering is used to improve the existing segmentation method of the pore-throat interval, eliminate the subjectivity in the segmentation process, and obtain a more accurate distribution curve of the pore-throat. For the three kinds of cores with ordinary-low permeability (K > 1 mD), ultra-low permeability (0.1 mD < K < 1 mD), and super-low permeability (K < 0.1 mD), the pore-throat distribution curves of the cores were obtained by using the improved T<sub>2</sub> conversion method. Then, the oil and gas two-phase displacement experiment was carried out to investigate the degree of recovery and cumulative gas–oil ratio changes during the displacement process. Finally, the converted T<sub>2</sub> spectrum was used to quantify the utilization of different pore sizes. The improved T<sub>2</sub> conversion method not only has better accuracy but also is not limited by the pore-throat distribution types (such as unimodal, bimodal, and multi-modal, etc.) and is suitable for any core with measured HPMI pore-throat distribution and an NMR T<sub>2</sub> spectrum. Combined with the results of core displacement and the degree of pore-throat utilization, it is found that the potential of miscible flooding to improve the recovery degree is in the order of ordinary-low permeability core (18–22%), ultra-low permeability core (25–29%), and super-low permeability core (8–12%). The utilization degree of immiscible flooding to the <10 nm pore-throat is low (up to 35%), while miscible flooding can effectively use the <3.7 nm pore-throat (up to 73%). The development effect of supercritical CO<sub>2</sub> flooding on K < 0.1 mD reservoirs is not good, the seepage resistance of CO<sub>2</sub> is large, the miscible flooding makes it difficult to improve the recovery degree, and the utilization effect of pore-throat is poor. |
| format | Article |
| id | doaj-art-eb85da9f7bf84043935dd88f2d1839d3 |
| institution | Kabale University |
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| publishDate | 2025-01-01 |
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| spelling | doaj-art-eb85da9f7bf84043935dd88f2d1839d32025-01-24T13:20:37ZengMDPI AGApplied Sciences2076-34172025-01-0115273010.3390/app15020730A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability CoresYanchun Su0Chunhua Zhao1Xianjie Li2Xiujun Wang3Jian Zhang4Bo Huang5Xiaofeng Tian6Mingxi Liu7Kaoping Song8State Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaState Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100027, ChinaNational Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, ChinaNational Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, ChinaNuclear magnetic resonance (NMR) and high-pressure mercury injection (HPMI) have been widely used as common characterization methods of pore-throat. It is generally believed that there is a power function relationship between transverse relaxation time (T<sub>2</sub>) and pore-throat radius (r), but the segmentation process of the pore-throat interval is subjective, which affects the conversion accuracy. In this paper, ordered clustering is used to improve the existing segmentation method of the pore-throat interval, eliminate the subjectivity in the segmentation process, and obtain a more accurate distribution curve of the pore-throat. For the three kinds of cores with ordinary-low permeability (K > 1 mD), ultra-low permeability (0.1 mD < K < 1 mD), and super-low permeability (K < 0.1 mD), the pore-throat distribution curves of the cores were obtained by using the improved T<sub>2</sub> conversion method. Then, the oil and gas two-phase displacement experiment was carried out to investigate the degree of recovery and cumulative gas–oil ratio changes during the displacement process. Finally, the converted T<sub>2</sub> spectrum was used to quantify the utilization of different pore sizes. The improved T<sub>2</sub> conversion method not only has better accuracy but also is not limited by the pore-throat distribution types (such as unimodal, bimodal, and multi-modal, etc.) and is suitable for any core with measured HPMI pore-throat distribution and an NMR T<sub>2</sub> spectrum. Combined with the results of core displacement and the degree of pore-throat utilization, it is found that the potential of miscible flooding to improve the recovery degree is in the order of ordinary-low permeability core (18–22%), ultra-low permeability core (25–29%), and super-low permeability core (8–12%). The utilization degree of immiscible flooding to the <10 nm pore-throat is low (up to 35%), while miscible flooding can effectively use the <3.7 nm pore-throat (up to 73%). The development effect of supercritical CO<sub>2</sub> flooding on K < 0.1 mD reservoirs is not good, the seepage resistance of CO<sub>2</sub> is large, the miscible flooding makes it difficult to improve the recovery degree, and the utilization effect of pore-throat is poor.https://www.mdpi.com/2076-3417/15/2/730low permeability coreT<sub>2</sub> conversion methodpore-throat radius rangeordered clusteringCO<sub>2</sub> flooding experimentthe degree of pore-throat utilization |
| spellingShingle | Yanchun Su Chunhua Zhao Xianjie Li Xiujun Wang Jian Zhang Bo Huang Xiaofeng Tian Mingxi Liu Kaoping Song A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores Applied Sciences low permeability core T<sub>2</sub> conversion method pore-throat radius range ordered clustering CO<sub>2</sub> flooding experiment the degree of pore-throat utilization |
| title | A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores |
| title_full | A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores |
| title_fullStr | A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores |
| title_full_unstemmed | A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores |
| title_short | A New Transformation Method of the T<sub>2</sub> Spectrum Based on Ordered Clustering—A Case Study on the Pore-Throat Utilization Rule of Supercritical CO<sub>2</sub> Flooding in Low Permeability Cores |
| title_sort | new transformation method of the t sub 2 sub spectrum based on ordered clustering a case study on the pore throat utilization rule of supercritical co sub 2 sub flooding in low permeability cores |
| topic | low permeability core T<sub>2</sub> conversion method pore-throat radius range ordered clustering CO<sub>2</sub> flooding experiment the degree of pore-throat utilization |
| url | https://www.mdpi.com/2076-3417/15/2/730 |
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