A NEW INDEX FOR THE MATURITY OF CRUDE OIL AND HYDROCARBON SOURCE ROCK——METHYLDIADAMANTANE INDEX

Based on the forming mechanism of diadamantane,the thermal evolution relation among isomers as well as the actual GC-MS detection results of diadamantane-type compounds in the saturated hydrocarbon components of T-J source rock from the Shuanghu area of Tibet,five diadamantane indexes are put forward.By correlation analysis with R^O,it is suggested that methyldiadamantane index(MDII) can be applied as a new maturity parameter for source rock.On the basis of thermal modeling experiments with the lignite (R^O=0.46%) from Baise,Guangxi,the thermal evolution rules of MDII are discussed.MDII has good positive correlation with R^O,and their correlation coefficient is 0.83.As the index for the thermal maturity of organic matter,MDII is applied within the limits of mature and high mature stages.