川东北地区酸性气体中CO_2成因与TSR作用影响  

Origin of Sour Gas in the Northeastern Sichuan Basin and Fate Action of Thermochemical Sulfate Reduction(TSR) to Natural Gas

作　　者：刘全有[1] 金之钧[1] 高波[1] 张殿伟[1] 胡安平[2] 杨春[2] 李剑[3] 

机构地区：[1]中石化石油勘探开发研究院,北京100083 [2]浙江大学地球科学系,杭州310027 [3]中国石油勘探开发研究院廊坊分院,河北廊坊065007

出　　处：《地质学报》2009年第8期1195-1202,共8页Acta Geologica Sinica

基　　金：国家自然科学基金(编号40802028);重点基础研究发展规划项目(编号2005CB422108)资助成果

摘　　要：通过对川东北地区52个天然气样品化学组分和稳定碳同位素分析,天然气以烃类气体为主,且甲烷占绝对高含量,重烃气体甚微,干燥系数C1/C1+为0.989～1.0。非烃气体H2S和CO2含量变化较大,当二者含量大于5.0%时,具有较好的正相关性。川东北地区天然气中CO2主要包括碳酸盐岩热分解和TSR作用,其中碳酸盐岩热分解生成的CO2含量一般小于5.0%,δ13CCO2值小于-2‰,且CO2含量与δ13CCO2值具有正相关性;而TSR作用生成的CO2含量大于5.0%,δ13CCO2值多大于-2‰,且CO2含量与δ13CCO2值具有较弱的负相关性。CH4/CO2值和(H2S+CO2)/(H2S+CO2+∑C1-3)值能够较好地反映TSR作用程度;当CH4/CO2值和(H2S+CO2)/(H2S+CO2+∑C1-3)值分别小于10和大于0.1时,随着TSR作用增强,CH4/CO2值减少,而(H2S+CO2)/(H2S+CO2+∑C1-3)值呈指数增加。同时,遭受TSR作用改造的天然气具有较高CO2含量和重的δ13CCO2,造成δ13CCO2值与实验结果不一致性的可能原因是在TSR反应过程中部分CO2与硫酸盐中Mg2+、Fe2+和Ca2+等金属离子以碳酸盐的形式沉淀且残余的重碳同位素组成的CO与酸性气体腐蚀碳酸盐储层形成的CO相混合。of chemical and stable carbon isotopic compositions on 74 gas samples from the northeastern Sichuan basin shows that natural gas is dominated by hydrocarbon gases, with absolutely high content of methane and tiny amount of heavy hydrocarbons （i. e C2 H6, C3 H8） . The gas dryness C1/C1＋ ranges from 0. 989 to 1.0. The concentrations of H2 S and CO2 vary greatly, and show a distinct positive correlation when the concentrations are higher than 5.0%. CO2 in the northeastern Sichuan basin is derived from thermal decompostion of carbonatic rock and thermochemical sulfate reduction to hydrocarbons. The CO2 deocmposed from carbonatic rock is characterized by a low CO2 content （generally less than 5.0 %）, δ^13 CCO2-2%o and THE positive correlation between CO2 content and δ^13 CCO2 value. In contrast, the CO2 generating from TSR has a high CO2content （generally more than 5.0%）, much high ^13C carbon isotope （δ^13 CCO2 -2‰） and a weakly negative correlation between CO2 and δ^13 CCO2. The TSR level can be well described by ratios of CH4/CO2 and （H2 S ＋ CO2 ） / （H2S ＋ CO2 ＋ ∑1-3 ）. When the ratios of CH4/CO2 and （H2S＋CO2）/（H2S＋CO2＋f-∑13）is less and more than 10 and 0.1, respectively, the decrease of CH4/CO2 ratios and exponential increase of （ H2 S ＋ CO2 ）/（ H2 S＋ CO2 ＋ Co 3 ） is observed with the increasing TSR. Meanwhile, the gas suffering TSR contains a high content of CO2 and much less negative of δ^13 CCO2 values. The discrepancy of δ^13 CCO2 values between natural and pyrolysis gases might be related to the precipitation of partial CO2 reaction with metal ions such as Mg^2＋. Fe^2＋ and Ca^2＋ as carbonate and mixing of CO2 containing remnant heavy carbon isotope with CO2 derived from erosion of sour gas on carbonate reservoir.

关 键 词：川东北地区 酸性气体 CO2成因 TSR作用 地球化学 

分 类 号：P618.13[天文地球—矿床学]