CAJ | 학술논문

对四川盆地东部50个天然气样品组分和碳、氢同位素组成分析结果显示，天然气以烃类气体为主，干燥系数高（C 1／C 1＋＝0．975～1．0），H2 S 含量变化较大（H2 S ＝0．00％～16．89％）。利用烷烃气碳、氢同位素组成和判识油型气热演化程度图版，确定四川盆地东部天然气主要为原油裂解气，且热演化程度已处于油气裂解阶段。在四川盆地东部，烷烃气碳、氢同位素组成普遍存在局部倒转现象，即δ13C 1＞δ13C 2＜δ13C 3和δD 1＞δD2，这主要与研究区域不同硫酸盐热化学还原作用（TSR）强度有关，因为在该反应过程中不仅会产生大量的 CH4，其碳同位素较重，同时，水参与了硫酸盐与烃类的化学还原反应使得水中的H ＋与烃类中 H ＋发生同位素交换，从而引起 TSR 生成 CH4的氢同位素分馏大于干酪根直接生烃过程造成的氢同位素分馏。异常δ13C CO 2值与 TSR 反应过程中部分碳同位素较轻的 CO2与硫酸盐中金属离子（Mg2＋、Fe 2＋、Ca2＋等）以碳酸盐的形式沉淀后，导致气藏中残余重碳同位素组成的 CO2与酸性气体腐蚀碳酸盐岩储集层形成的 CO2相混合有关。
대사천분지동부50개천연기양품조분화탄、경동위소조성분석결과현시，천연기이경류기체위주，간조계수고（C 1／C 1＋＝0．975～1．0），H2 S 함량변화교대（H2 S ＝0．00％～16．89％）。이용완경기탄、경동위소조성화판식유형기열연화정도도판，학정사천분지동부천연기주요위원유렬해기，차열연화정도이처우유기렬해계단。재사천분지동부，완경기탄、경동위소조성보편존재국부도전현상，즉δ13C 1＞δ13C 2＜δ13C 3화δD 1＞δD2，저주요여연구구역불동류산염열화학환원작용（TSR）강도유관，인위재해반응과정중불부회산생대량적 CH4，기탄동위소교중，동시，수삼여료류산염여경류적화학환원반응사득수중적H ＋여경류중 H ＋발생동위소교환，종이인기 TSR 생성 CH4적경동위소분류대우간락근직접생경과정조성적경동위소분류。이상δ13C CO 2치여 TSR 반응과정중부분탄동위소교경적 CO2여류산염중금속리자（Mg2＋、Fe 2＋、Ca2＋등）이탄산염적형식침정후，도치기장중잔여중탄동위소조성적 CO2여산성기체부식탄산염암저집층형성적 CO2상혼합유관。
According to gas chemical and carbon and hydrogen isotopic compositions for 50 gas samples from the eastern Sichuan Basin,the natural gas mainly consists of hydrocarbon gas with high dryness coefficient(C 1 /C 1 +=0.975 ~1.0) and various H 2 S contents (H 2 S =0.00% ~16.89%),and the hydrocarbon gas was mainly derived from secondary cracking of oil and gas.In the eastern Sichuan Basin,the phenomenon of partial reversal for stable carbon and hydrogen isotopes of gaseous alkane is widespread,i.e.,δ13C 1 >δ13C 2 <δ13C 3 and δD 1 >δD 2 .This abnormality of carbon and hydrogen isotopic composition is mainly caused by different extent of thermochemical sulfate reduction (TSR)alteration.The TSR process produces a large amount of methane,which enriches heavy carbon isotope.The H +isotopic exchange between H 2 O and hydrocarbons during the TSR process resulted in that hydrogen isotope fractionation in methane produced from TSR is higher than directly from hydrocarbon generation.The CO 2 with abnormal δ13C and CO 2 generated from calcite dissolution during TSR process,which has a relatively light carbon isotope composition,precipitated with metal ions in sulfate,such as Mg2+,Fe 2+ and Ca2+,to form carbonates.