The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China

The Chang 8 tight reservoir in the area of Jiyuan holds characteristics such as high feldspar content and common feldspar dissolution phenomenon, which are vital to improve the physical properties of tight reservoirs. This paper simulates the interaction between the Chang 8 tight reservoir rock samp...

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Main Authors: Shutong Li, Jingli Yao, Weiwei Mou, Anxiang Luo, Qi Wang, Xiuqin Deng, Meijuan Chu, Yang Li, Cancan Yan
Format: Article
Language:English
Published: KeAi Communications Co., Ltd. 2018-04-01
Series:Journal of Natural Gas Geoscience
Online Access:http://www.sciencedirect.com/science/article/pii/S2468256X18300221
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author Shutong Li
Jingli Yao
Weiwei Mou
Anxiang Luo
Qi Wang
Xiuqin Deng
Meijuan Chu
Yang Li
Cancan Yan
author_facet Shutong Li
Jingli Yao
Weiwei Mou
Anxiang Luo
Qi Wang
Xiuqin Deng
Meijuan Chu
Yang Li
Cancan Yan
author_sort Shutong Li
collection DOAJ
description The Chang 8 tight reservoir in the area of Jiyuan holds characteristics such as high feldspar content and common feldspar dissolution phenomenon, which are vital to improve the physical properties of tight reservoirs. This paper simulates the interaction between the Chang 8 tight reservoir rock samples and organic acid, analyzes the types and characteristics of dissolution, explains the dissolution mechanism, and quantitatively calculates the influence of dissolution on the porosity of the reservoir on the basis of identifying the fundamental characteristics of the Chang 8 tight reservoir by utilizing the simulation experiment of fluid–rock interaction with high temperature and high pressure combined with polarized microscope and scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis techniques. With the purpose of making the simulation experiment closer to the actual geological conditions, 0.15 mol/L acetic acid solution with pH = 2.65 is used as the reaction fluid, wherein the simulated temperature range is set to 87–103 °C, and the simulated pressure range is set to 24.70–30.18 MPa. The result of the research shows that intergranular pores and feldspar dissolved pores are the primary pore types. The feldspar dissolved pores are more developed and accounts for 39% of the total porosity. The apparent solution ratio is 37.8%–50.0% with a moderate degree of dissolution. Additionally, carbonate minerals can also be dissolved in an acidic condition. The solution ratio of carbonate minerals generally exceeds that of feldspar. The dissolution degree is most robust at about 95 °C, and the burial depth is about 2370–2710 m by the geothermal gradient calculation, which should be the primary distribution area of the favorable tight reservoir of the Chang 8. Overall, dissolution is the main diagenesis type to improve the porosity that can result in the porosity increasing about 3.57%–3.69% in the tight reservoirs of Chang 8. Therefore, it is also the main controlling factor for the development of the ''dessert'' in the Chang 8 tight reservoir of western Jiyuan area. Keywords: Tight reservoir, Dissolution, Fluid-rock interaction, Simulation experiment, Chang 8, Jiyuan area
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spelling doaj.art-045ad1d2cf964082881ce5e70a43f1432023-09-02T12:43:57ZengKeAi Communications Co., Ltd.Journal of Natural Gas Geoscience2468-256X2018-04-013295108The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, ChinaShutong Li0Jingli Yao1Weiwei Mou2Anxiang Luo3Qi Wang4Xiuqin Deng5Meijuan Chu6Yang Li7Cancan Yan8Key Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou, 730000, China; Corresponding author.Exploration and Development Research Institution, Changqing Oilfield Company, Xi'an, 710021, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou, 730000, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Corresponding author. University of Chinese Academy of Sciences, Beijing, 100049, China.Exploration and Development Research Institution, Changqing Oilfield Company, Xi'an, 710021, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou, 730000, ChinaExploration and Development Research Institution, Changqing Oilfield Company, Xi'an, 710021, ChinaExploration and Development Research Institution, Changqing Oilfield Company, Xi'an, 710021, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou, 730000, China; University of Chinese Academy of Sciences, Beijing, 100049, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou, 730000, China; University of Chinese Academy of Sciences, Beijing, 100049, ChinaThe Chang 8 tight reservoir in the area of Jiyuan holds characteristics such as high feldspar content and common feldspar dissolution phenomenon, which are vital to improve the physical properties of tight reservoirs. This paper simulates the interaction between the Chang 8 tight reservoir rock samples and organic acid, analyzes the types and characteristics of dissolution, explains the dissolution mechanism, and quantitatively calculates the influence of dissolution on the porosity of the reservoir on the basis of identifying the fundamental characteristics of the Chang 8 tight reservoir by utilizing the simulation experiment of fluid–rock interaction with high temperature and high pressure combined with polarized microscope and scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis techniques. With the purpose of making the simulation experiment closer to the actual geological conditions, 0.15 mol/L acetic acid solution with pH = 2.65 is used as the reaction fluid, wherein the simulated temperature range is set to 87–103 °C, and the simulated pressure range is set to 24.70–30.18 MPa. The result of the research shows that intergranular pores and feldspar dissolved pores are the primary pore types. The feldspar dissolved pores are more developed and accounts for 39% of the total porosity. The apparent solution ratio is 37.8%–50.0% with a moderate degree of dissolution. Additionally, carbonate minerals can also be dissolved in an acidic condition. The solution ratio of carbonate minerals generally exceeds that of feldspar. The dissolution degree is most robust at about 95 °C, and the burial depth is about 2370–2710 m by the geothermal gradient calculation, which should be the primary distribution area of the favorable tight reservoir of the Chang 8. Overall, dissolution is the main diagenesis type to improve the porosity that can result in the porosity increasing about 3.57%–3.69% in the tight reservoirs of Chang 8. Therefore, it is also the main controlling factor for the development of the ''dessert'' in the Chang 8 tight reservoir of western Jiyuan area. Keywords: Tight reservoir, Dissolution, Fluid-rock interaction, Simulation experiment, Chang 8, Jiyuan areahttp://www.sciencedirect.com/science/article/pii/S2468256X18300221
spellingShingle Shutong Li
Jingli Yao
Weiwei Mou
Anxiang Luo
Qi Wang
Xiuqin Deng
Meijuan Chu
Yang Li
Cancan Yan
The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
Journal of Natural Gas Geoscience
title The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
title_full The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
title_fullStr The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
title_full_unstemmed The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
title_short The dissolution characteristics of the Chang 8 tight reservoir and its quantitative influence on porosity in the Jiyuan area, Ordos Basin, China
title_sort dissolution characteristics of the chang 8 tight reservoir and its quantitative influence on porosity in the jiyuan area ordos basin china
url http://www.sciencedirect.com/science/article/pii/S2468256X18300221
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