计算烃类成熟度史的实地TTI-R_o法

A practical TTI-R_ o method for hydrocarbon maturity history reconstruction.

目前盆地模拟中重建烃类成熟度史时 ,一般只制作单一TTI(时间温度指数 ) Ro(镜质组反射率 )公式 ,不仅使成熟度史的误差较大 ,还有明显的概念错误。提出实地TTI Ro法 :首先根据地史模拟得到的埋藏史以及热史模拟得到的地温史求得TTI史 ,再根据实测的Ro以及各地层埋深最大时的TTI值 ,制作各地质时期的TTI Ro公式 ,此后便可求得烃类成熟度史。对比TTI Ro“通用公式”与中国临清坳陷某井和塔里木盆地某井的实地TTI Ro公式 ,差异很大 ,原因在于求取TTI史的公式假设有局限性 ,而由于干酪根的组分和化学键的复杂性 ,以及不同地区地质条件和生烃母质的差异性 ,不同地区的TTI生烃门限和TTI Ro公式都不同。应用TTI Ro法研究烃类成熟度史时 ,必须注意TTI的局限性和Ro的不良定标等问题。图 3表

When the hydrocarbon maturity history is rebuilt in present basin modeling, usually the single TTI (time temperature index) R o (vitrinite reflectance) formula is only used, which may cause the bigger error of R o history and obvious wrong concept. Therefore, the author presents a practical TTI R o method, the process of which is to firstly calculate the TTI history on the basis of the burial history from geohistory model and the temperature history from geothermal history model, and then to construct the R o TTI formulas for each geological period according to the field measured R o and TTI at the maximum burial depth of each formation, and finally to work out the R o history that is the hydrocarbon maturity history. Comprising the 'general purpose formula' with the practical TTI R o formulas from a well of Linqing depression and a well of Tarim basin, the bigger differences are found. These differences are come from the following two aspects: (1) the limitation of the assumption of the formula to calculate the TTI history due to the complexity of composition and chemical bonding in kerogen; and (2) the hydrocarbon generation thresholds of TTI and TTI R o formulas being both different in different areas due to the different geological condition and matrix in the different areas. In addition, limitation of TTI , poor calibration of R o should be noted.