页岩气资源/储量计算中吸附参数确定的新方法——以四川盆地五峰组—龙马溪组页岩为例  

A novel method for determining adsorption parameters in shale gas resources/reserves calculation:A case study of the Wufeng Formation-Longmaxi Formation in the Sichuan Basin

作　　者：赵群[1,2] 周天琪 王红岩 金亦秋[3] 周尚文 端祥刚 ZHAO Qun;ZHOU Tianqi;WANG Hongyan;JIN Yiqiu;ZHOU Shangwen;DUAN Xianggang(PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;National Energy Shale Gas R&D(Experiment)Center,Langfang,Hebei 065007,China;PetroChina Oil,Gas and New Energy Company,Beijing 100007,China)

机构地区：[1]中国石油勘探开发研究院 [2]国家能源页岩气研发(实验)中心 [3]中国石油油气与新能源公司

出　　处：《天然气工业》2023年第1期47-54,共8页Natural Gas Industry

基　　金：中国石油天然气股份有限公司科学研究与技术开发项目“页岩气开发区地质活动性评价技术研究”(编号:2022DJ80);“海相页岩气勘探开发技术研究”(编号:2021DJ19)。

摘　　要：页岩气资源/储量计算过程中,等温吸附参数的确定主要采用实验温度条件下的干燥样品数据,并存在总有机碳含量(TOC)和等温吸附参数回归效果差的问题。为此,以四川盆地上奥陶统五峰组—下志留统龙马溪组海相页岩为例,从Langmuir吸附模型和Henry吸附模型中关键参数的物理意义出发,分析了页岩气资源/储量计算过程中等温吸附参数确定中存在的问题,并基于大量等温吸附实测数据,分析影响页岩气吸附参数的TOC、温度和含水饱和度等因素,建立了TOC、温度和含水饱和度对页岩等温吸附参数的影响模型,提出了从实验条件到储层原始条件下页岩气吸附参数计算的新方法。研究结果表明:①页岩气资源/储量计算过程中存在等温吸附参数与TOC关系拟合规律差且互有矛盾、范特霍夫方程难以有效转换、含水饱和度(S_(w))在资源/储量计算中不易直接应用等问题。②将Langmuir吸附模型和Henry吸附模型结合,建立页岩对甲烷的吸附能力新参数Henry常数a,有效地解决了Langmuir压力(pL)与TOC直接拟合效果不佳的问题。③当S_(w)<40%时,Langmuir体积(V_(L))与S_(w)呈线性负相关;当S_(w)<20%时a值相对恒定;通过建立压力超过30 MPa时归一化绝对吸附量与S_(w)(小于50%)关系,可有效地解决S_(w)对等温吸附量计算结果的影响。(4)五峰组—龙马溪组页岩储层地应力大小影响页岩的吸附能力,相同TOC页岩的储层地应力越大,V_(L)越小,a值越低;在高压条件下(大于30 MPa),S_(w)对页岩甲烷吸附能力的影响具有相似趋势,水分子对页岩孔隙表面吸附位的影响恒定。结论认为,提出的不同TOC、不同温度和不同含水饱和度条件下页岩等温吸附参数确定的新方法,可以为页岩气资源/储量的精准计算提供技术支撑,将有助于页岩气产业的科学发展。In the calculation of shale gas resources/reserves,isothermal adsorption parameters are mainly determined by dry sample data at the laboratory temperature,and the regression effect of total organic carbon content(TOC)isothermal adsorption parameters is poor.Based on the physical significance of key parameters in Langmuir and Henry adsorption models,the problems in determining the isothermal adsorption parameters in the calculation of shale gas reserves/reserves are analyzed by taking the marine shale in the Upper Ordovician Wufeng Forming–Lower Silurian Longmaxi Formation in the Sichuan Basin as an example.Based on a large number of measured isothermal adsorption data,the effects of TOC,temperature and water saturation on the shale gas adsorption parameters are analyzed.The influence model of TOC,temperature and water saturation on isothermal adsorption parameters of shale gas is established,and a novel method for calculating the adsorption parameters of shale gas from under experimental conditions to original reservoir conditions is proposed.The results are obtained as follows.First,there are problems in the calculation of shale gas resources/reserves,such as poor and contradictory fitting relation between isothermal adsorption parameters and TOC,difficulty in the conversion of Van’t Hoff equation,and difficulty in direct application of water saturation(S_(w))in resource/reserves calculation.Second,the problem of poor direct fitting relation between Langmuir pressure(PL)and TOC is solved by integrating the Langmuir adsorption model with the Henry adsorption model and by establishing a new parameter–Henry constant a for methane adsorption capacity of shale.Third,when S_(w)<40%,the Langmuir volume(V_(L))is linearly negatively correlated with S_(w);when S_(w)<20%,a is constant relatively;by establishing the relationship between the normalized absolute adsorption capacity and S_(w)(<50%)under the pressure exceeding 30 MPa,the effect of S_(w)on the isothermal adsorption capacity can be calculated.Fourth,the in-

关 键 词：页岩气 LANGMUIR模型 Henry模型 等温吸附 含水饱和度 资源/储量计算 

分 类 号：P618.13[天文地球—矿床学]