四川盆地长宁地区海相页岩吸附气含量演化特征--以N201井五峰组-龙马溪组一段为例

Evolution of adsorbed gas content of marine shale in Changning area,Sichuan Basin:a case of Wufeng Formation-Longmaxi Member 1 in Well N201

吸附气是页岩气的重要赋存形式和组成部分。为了明确四川盆地长宁地区五峰组—龙马溪组一段页岩在埋藏过程中吸附气含量的演化规律,利用页岩等温吸附实验、钻井现场解吸和测井综合解释资料,建立了页岩吸附气含量与地层温度、地层压力、页岩TOC等主要影响参数的多元回归数学公式,结合典型评价井(N201井)的埋藏史、热史,对不同地质时期页岩吸附气含量进行定量计算。计算结果表明:自侏罗纪有机质开始大量生气以来,页岩吸附气含量随着埋藏深度的增加逐渐升高,到白垩纪末期吸附气含量达到4.42 m^(3)/t;古近纪以来,随着上覆地层被大幅度剥蚀,页岩吸附气含量逐渐降低至现今的1.67 m^(3)/t。

Adsorbed gas is an important occurrence form and component of shale gas.In order to clarify the evolution law of adsorbed gas content in shale burial process in Changning area of Sichuan Basin,using data of shale isotherm adsorption experiment,drilling site desorption,and logging comprehensive interpretation,a multiple regression equation of adsorbed gas content with main influencing parameters such as formation temperature,formation pressure and TOC is setup.On this basis,combined with the recovery of the burial history and thermal history of typical evaluation Well N201,the shale adsorbed gas content in different geological periods is quantitatively calculated.The calculation results show that shale organic matter began to generate large amounts of gas in Jurassic,the shale-adsorbed gas content gradually increased with the increase of burial depth,and reached 4.42 m3/t at the end of Late Cretaceous.Since Paleogene,with the overlying strata being largely denuded,the shale adsorbed gas content gradually decreased to 1.67m3/t at present.