原油裂解气和干酪根裂解气的判识

中国中西部的叠合盆地中,下古生界海相烃源岩已达高过成熟阶段,但却发现大量与之有关的原油裂解气.因此,如何区分原油裂解气和干酪根裂解气,成了一个亟需解决的问题.从天然气组分和轻烃组分切入,应用ln(C2/C3)-ln(C1/C2)判识模式及δ13C2-δ13C3与ln(C2/C3)判识模式认为四川盆地川东地区石炭系气藏为原油裂解气,而塔里木盆地轮南断垒和中部斜坡的气藏为干酪根裂解气.根据对典型干酪根和原油裂解气的分析,结合热模拟分析结果,提出了3项轻烃判识原油裂解气和干酪根裂解气界限值指标.

Identification of oil-cracking gas and kerogen-cracking gas

The marine source rock in the superimposed basins in middle-west China is highly over-mature,but a large number of oil-cracking gas related with it is founded.Therefore,it is important to distinguish the oil-cracking gas from kerogen-cracking gas.Based on the compositions of natural gas,they can be identified according to the relationship between ln(C2/C3) and ln(C1/C2) and the relationship between δ13C2-δ13C3 and ln(C2/C3).The identification results show that the gas from the Carboniferous gas reservoirs in the east of Sichuan Basin is oil-cracking gas and the gas from the gas reservoirs in Lunnan Block and the central slope of Tarim Basin is kerogen-cracking gas.Based on the compositions of light hydrocarbons,they can be identified according to three indexes of methyl-cyclohexane / cyclohexane,(2-methyl-hexane+3-methyl-hexane) / n-hexane and methyl-cyclohexane / n-heptane.The 3 threshold values for distinguishing oil-cracking gas from kerogen-cracking gas are proposed.