{"title":"富有机质页岩微孔中天然气自扩散耦合吸附与地质力学效应模拟","authors":"Clement Afagwu , Saad Alafnan , Mohamed Mahmoud , I. Yucel Akkutlu","doi":"10.1016/j.jngse.2022.104757","DOIUrl":null,"url":null,"abstract":"<div><p><span><span><span>A significant amount of the natural gas in shale formations is contained in the micro- and mesopores as dissolved (absorbed) phase and on the surfaces of associated </span>microcracks<span> as (adsorbed) phase. The transport of natural gas in such confined spaces is primarily governed by self-diffusion as could be deduced from Knudsen number<span>. Self-diffusion is governed by the pressure and the space confinement. In this study, realistic kerogen structures possessing both tortuous micropores and larger microcracks were formed and used to assess self-diffusion behavior during the depletion of shale reservoirs through some comprehensive molecular simulation workflow. Analysis of the transport modes revealed transition self-diffusion as the primary transport mechanism in these micropores. The sorption behavior and the mechanical properties were analyzed and incorporated to derive a transition </span></span></span>diffusion model that is sensitive to changes in the </span>pore pressure<span><span> and the stress field. The proposed model was compared and validated against similar work in the literature. The results showed that during a typical production span, a pressure drop influences the sorption profile, the net overburden stress on the pores, and the </span>mean free path<span>, altering the magnitude of self-diffusivity. The calibrated pore scale<span><span><span> model produced decent predictive ability with a relative error of 2.5–16%. The implications of structure </span>tortuosity, sorption profile, and pore pressure on the effective </span>diffusion coefficient<span> and gas desorption are discussed in depth. This work provides a novel methodology for studying the effect of coupled multiphysics processes on methane transport in a realistic kerogen geometry, which could be used to calibrate a suitable pore scale model for upscaled reservoir simulation applications and accurate assessment of reservoir dynamics and ultimate recovery.</span></span></span></span></p></div>","PeriodicalId":372,"journal":{"name":"Journal of Natural Gas Science and Engineering","volume":"106 ","pages":"Article 104757"},"PeriodicalIF":4.9000,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"9","resultStr":"{\"title\":\"Modeling of natural gas self-diffusion in the micro-pores of organic-rich shales coupling sorption and geomechanical effects\",\"authors\":\"Clement Afagwu , Saad Alafnan , Mohamed Mahmoud , I. Yucel Akkutlu\",\"doi\":\"10.1016/j.jngse.2022.104757\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p><span><span><span>A significant amount of the natural gas in shale formations is contained in the micro- and mesopores as dissolved (absorbed) phase and on the surfaces of associated </span>microcracks<span> as (adsorbed) phase. The transport of natural gas in such confined spaces is primarily governed by self-diffusion as could be deduced from Knudsen number<span>. Self-diffusion is governed by the pressure and the space confinement. In this study, realistic kerogen structures possessing both tortuous micropores and larger microcracks were formed and used to assess self-diffusion behavior during the depletion of shale reservoirs through some comprehensive molecular simulation workflow. Analysis of the transport modes revealed transition self-diffusion as the primary transport mechanism in these micropores. The sorption behavior and the mechanical properties were analyzed and incorporated to derive a transition </span></span></span>diffusion model that is sensitive to changes in the </span>pore pressure<span><span> and the stress field. The proposed model was compared and validated against similar work in the literature. The results showed that during a typical production span, a pressure drop influences the sorption profile, the net overburden stress on the pores, and the </span>mean free path<span>, altering the magnitude of self-diffusivity. The calibrated pore scale<span><span><span> model produced decent predictive ability with a relative error of 2.5–16%. The implications of structure </span>tortuosity, sorption profile, and pore pressure on the effective </span>diffusion coefficient<span> and gas desorption are discussed in depth. This work provides a novel methodology for studying the effect of coupled multiphysics processes on methane transport in a realistic kerogen geometry, which could be used to calibrate a suitable pore scale model for upscaled reservoir simulation applications and accurate assessment of reservoir dynamics and ultimate recovery.</span></span></span></span></p></div>\",\"PeriodicalId\":372,\"journal\":{\"name\":\"Journal of Natural Gas Science and Engineering\",\"volume\":\"106 \",\"pages\":\"Article 104757\"},\"PeriodicalIF\":4.9000,\"publicationDate\":\"2022-10-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"9\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Natural Gas Science and Engineering\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1875510022003444\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ENERGY & FUELS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Natural Gas Science and Engineering","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1875510022003444","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
Modeling of natural gas self-diffusion in the micro-pores of organic-rich shales coupling sorption and geomechanical effects
A significant amount of the natural gas in shale formations is contained in the micro- and mesopores as dissolved (absorbed) phase and on the surfaces of associated microcracks as (adsorbed) phase. The transport of natural gas in such confined spaces is primarily governed by self-diffusion as could be deduced from Knudsen number. Self-diffusion is governed by the pressure and the space confinement. In this study, realistic kerogen structures possessing both tortuous micropores and larger microcracks were formed and used to assess self-diffusion behavior during the depletion of shale reservoirs through some comprehensive molecular simulation workflow. Analysis of the transport modes revealed transition self-diffusion as the primary transport mechanism in these micropores. The sorption behavior and the mechanical properties were analyzed and incorporated to derive a transition diffusion model that is sensitive to changes in the pore pressure and the stress field. The proposed model was compared and validated against similar work in the literature. The results showed that during a typical production span, a pressure drop influences the sorption profile, the net overburden stress on the pores, and the mean free path, altering the magnitude of self-diffusivity. The calibrated pore scale model produced decent predictive ability with a relative error of 2.5–16%. The implications of structure tortuosity, sorption profile, and pore pressure on the effective diffusion coefficient and gas desorption are discussed in depth. This work provides a novel methodology for studying the effect of coupled multiphysics processes on methane transport in a realistic kerogen geometry, which could be used to calibrate a suitable pore scale model for upscaled reservoir simulation applications and accurate assessment of reservoir dynamics and ultimate recovery.
期刊介绍:
The objective of the Journal of Natural Gas Science & Engineering is to bridge the gap between the engineering and the science of natural gas by publishing explicitly written articles intelligible to scientists and engineers working in any field of natural gas science and engineering from the reservoir to the market.
An attempt is made in all issues to balance the subject matter and to appeal to a broad readership. The Journal of Natural Gas Science & Engineering covers the fields of natural gas exploration, production, processing and transmission in its broadest possible sense. Topics include: origin and accumulation of natural gas; natural gas geochemistry; gas-reservoir engineering; well logging, testing and evaluation; mathematical modelling; enhanced gas recovery; thermodynamics and phase behaviour, gas-reservoir modelling and simulation; natural gas production engineering; primary and enhanced production from unconventional gas resources, subsurface issues related to coalbed methane, tight gas, shale gas, and hydrate production, formation evaluation; exploration methods, multiphase flow and flow assurance issues, novel processing (e.g., subsea) techniques, raw gas transmission methods, gas processing/LNG technologies, sales gas transmission and storage. The Journal of Natural Gas Science & Engineering will also focus on economical, environmental, management and safety issues related to natural gas production, processing and transportation.