A study from the Barnett in 2001 produced a conversion formula to calculate %Ro from Tmax data. The conversion formula (calculated Ro = 0.0180 x Tmax - 7.16) has been used extensively in basins worldwide despite the fact that the formula was especially produced for the Barnett shale; Is there any idea?
Dear Pezhman,
This formula is applicable for type II and type III kerogens. To obtain reasonable Ro data, the mentioned formula should not be used for samples that have S2 values smaller than 0.5 mg HC/g rock and samples with Tmax< 420 or >500°C.
Regards
Dear Rzger,
Thanks for the reply. Ok, but what if most of the samples have S2 values smaller than 0.5 HC/g rock? Is there any additional technique for calculating the reasonable Ro data?
Cheers,
Pezhman
Dear Rezhman,
Before converting Tmax to Ro, the rock-eval data for samples should be screened based on the conditions that are shown on table 3 and figure 2 in the attached paper. The Tmax values may be not reliable.
Regards
Dear Rzger,
Thanks for the prompt replies; I've well got how to calculate %Ro properly.
Regards,
Pezhman
Dear friends,
Personally, when I am working on a specific source rock, I first check if Tmax values are increasing regularly with depth, in order to check if the analytical data are dependable. If they are, I correlate Tmax versus R0 and calculate my own equation Tmax f(R0).. The same formula is not valid for all source rocks, but depends upon the type and composition of source rocks
Regards
MLB
Dear Max,
Thanks for your note. Yep, as you've mentioned, checking the increasing rate of Tmax values with respect to the depth values would confirm accuracy of the dataset.
Regards,
Pezhman
Dear Pezhman,
This is a general rule, but you should take facies change and hydrogen content into consideration. Low hydrogen index, organic matter, has high Tmax and high hydrogen index, organic matter, has low Tmax.
Regards
Dear Rzger,
Many thanks for your second comment. Yeah, it's also a good idea to find out the outlier Tmax data which is resulted from instrument or measurement errors.
Regards,
Pezhman
You are right Pezhman. Sometimes the result of dividing one small number by another small number would be big, and in reality it is not big.
@Rzger Abdula: Yeah ... To overcome the issue it is proposed to unit range the data so that the values can be comparable within a same range.
Dear Pezhman,
Like the transformation ratio of a type of organic matter, the same thing happens with the Tmax of pyrolysis, and everything will basically depend on two factors, the original products or precursors, which will give different types of chemical composition and maturity Thermal stability that it achieved in a given time.
Hello colleagues,
Is there any other work you can suggest from Ro and Tmax correlation for coal and coal sediments other than Lee and Sun (2014)?
Greetings
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