The mature process of organic matters in the middle part of the 3rd mem-ber of Shahejie Formation (Es

3

)

the major source rock in Dongying depres-sion

is described in terms of residual carbon.The threshold of maturity(ca.2

400m in depth and 100℃)

climax of oil generation(ca.3

100m in depth and 124℃)and the limits of major oil generation zone(the depth for the upper limit is equal to the threshold of maturity

the lower limit being about 3

700m

with temperature 147℃)are confirmed by calculation at the centre of Lijin seg in Dongying depression.At present

this centric part has entered into the end stage of oil generation

and it seems there is no more potential for petroleum generation.The result of calculation fits well with geochemical study

and the enrich.ment and properties of oil and gas

thus proved that this method works effec-tively in the area studied

and that it could be another manner in quantita-tire assessment of oil and gas resources.