{"id":15854,"date":"2022-02-03T10:26:41","date_gmt":"2022-02-03T02:26:41","guid":{"rendered":"http:\/\/learncmg.cn\/?p=15854"},"modified":"2022-02-03T10:26:41","modified_gmt":"2022-02-03T02:26:41","slug":"%e5%90%b8%e9%99%84%e8%a7%a3%e5%90%b8%e8%bf%9f%e6%bb%9e%e7%8e%b0%e8%b1%a1%e6%9c%ba%e7%90%86%e5%8f%8a%e5%85%b6%e5%af%b9%e9%a1%b5%e5%b2%a9%e6%b0%94%e5%bc%80%e5%8f%91%e7%9a%84%e5%bd%b1%e5%93%8d","status":"publish","type":"post","link":"http:\/\/learncmg.cn\/?p=15854","title":{"rendered":"5. \u5438\u9644\u89e3\u5438\u8fdf\u6ede\u73b0\u8c61\u673a\u7406\u53ca\u5176\u5bf9\u9875\u5ca9\u6c14\u5f00\u53d1\u7684\u5f71\u54cd\u203b"},"content":{"rendered":"
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Methane Adsorption-Desorption Hysteresis and Its Effect on Shale Gas Production<\/a><\/h3>\n

Abstract<\/strong><\/p>\n

Gas desorption is one of the major gas transport mechanisms in shale gas reservoirs. However, its actual contribution to gas production is often masked by the indiscriminate use of adsorption-derived parameters for desorbed gas volumes during gas production calculations at reservoir conditions. Traditionally, it is believed that gas adsorption is fully reversible at the high-pressure, high-temperature conditions found in shale gas reservoirs. However, research has shown that desorption isotherms are often different from, and often show hysteresis with their adsorption counterparts. But, the cause of this hysteresis behavior at high temperature and high pressure remains unclear. More importantly, the implications of sorption hysteresis on production performances of shale gas reservoirs have not been previously studied.<\/p>\n

In this study, adsorption and desorption isotherms of methane were studied at temperatures of 25oC, 40oC, 60oC, and 80oC and pressures up to 7MPa using the Particulate System\u2019s HPVA[1]II\u00ae 200 equipment first for a coal sample and then for shale samples from Ordovician Goldwyer Formation, Canning Basin, Western Australia. The coal sample was used to test the effect of equations of states (EOSs) on the measured isotherms and their subsequent applications. The use of coal eliminated the complexities of shale and isolated the effect of fluid densities resulting from the use of different EOSs. Six popular EOSs namely Peng[1]Robinson\u2019s (PR), Soave-Redlich-Wonk\u2019s (SRK) and their volume translated forms (PR[1]Peneloux and SRK-Peneloux), Soave\u2019s modified Benedict-Webb-Rubin\u2019s (SBWR), and Lee[1]Kesler\u2019s (LK) were used for data interpretation and the results were compared with those calculated by the equipment using Z-factors from the equipment\u2019s software implementation of McCarty and Arp\u2019s EOS for helium and Setzmann & Wagner\u2019s EOS for methane (a combination subsequently referred to as NIST-refprop\u00ae). The three-parameter Langmuir model was used to describe each of the adsorption isotherms and the results showed that all the equations of state tested gave varied deviations in the measured isotherms, calculated model parameters, observed type and degree of sorption hysteresis and original gas in-place because of the variations in the calculated Z-factors of both helium and methane relative to NIST[1]refprop. Consequently, the SWBR EOS was selected for studies involving the shale samples.<\/p>\n

Early pore saturation, indicated by maximum excess adsorptions at pressures in the neighbourhood of the critical pressure of methane, was also observed for all the shale samples. Consequently, the measured sorption isotherms could not be represented directly by three[1]parameter Langmuir model. Therefore, a two-step modelling approach was adopted. First, each excess adsorption isotherm was modelled using Dubinin\u2013Radushkevich (D-R) model to obtain the adsorbed phase density used to convert both the adsorption and desorption amounts to their absolute equivalents. In the second step, and based on the intended application of the results, the conventional Langmuir model was used to describe the resultant absolute adsorption and desorption isotherms. Significant hysteresis was observed for all samples at all temperatures, albeit the relationship between the size of the hysteresis and temperature was inconsistent.<\/p>\n

Desorption isotherms resulted in lower model parameters than the corresponding adsorption isotherms. For both processes, Langmuir volumes positively correlated with TOC contents but show no significant correlations with total clay contents. A novel ratio of total clay to TOC (i.e. clay-to-organic-carbon, COC) applied as a single predictor showed good correlations with Langmuir volumes (R2-values comparable to those of correlations with TOC). The size of the hysteresis, as well as the BET surface areas and pore volumes determined from low-pressure adsorption experiments, also showed significant correlations with TOC contents and COC.<\/p>\n

Lastly, a compositional 3D multiple interacting nested continua (MINC) model was developed in CMG-GEM\u00ae to test the effect of the observed hysteresis at reservoir conditions on shale gas production. For each sample, a base scenario, corresponding to a \u201cno-sorption\u201d case was compared against two other cases: one with adsorption Langmuir parameters (adsorption case) and the other with desorption Langmuir parameters (desorption case). The simulation results showed that while gas production can be significantly under-predicted if gas sorption is not considered, the use of adsorption isotherms in lieu of desorption can lead to over-prediction of gas production performances.<\/p>\n

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<\/p>\n<\/div>\n<\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"

Methane Adsorption-Desorption Hysteresis and Its EContinue Reading<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[159],"tags":[385,55],"_links":{"self":[{"href":"http:\/\/learncmg.cn\/index.php?rest_route=\/wp\/v2\/posts\/15854"}],"collection":[{"href":"http:\/\/learncmg.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/learncmg.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/learncmg.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/learncmg.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15854"}],"version-history":[{"count":0,"href":"http:\/\/learncmg.cn\/index.php?rest_route=\/wp\/v2\/posts\/15854\/revisions"}],"wp:attachment":[{"href":"http:\/\/learncmg.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15854"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/learncmg.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15854"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/learncmg.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}