The black shales is widely distributed in Proterozoic Xiamaling Formation of Yanshan area

making the Xiamaling Formation to be an important potential target for shale gas exploration. Field profile survey shows that several sets of diabase sill intruded into Xiamaling Formation

which has great influence on oil and gas accumulation. Therefore

the numerical simulation study on the influence of a set of diabase bed about 7 m thick on the maturity of host rock is carried out based on the measurement of th

e field section and bitumen reflectance of the neighbouring shales. The results show that the influence range of this diabase bed on

R

o

of organic matter in host rock is about 8.5 m

which is about 1.2 times of its own thickness. The measured

R

o

values increases exponentially near the bedrock. The numerical simulation results show that the diabase will cool down almost completely after 110 years

and the disturbance range to the surrounding rock geothermal field is about 100 m

which is much larger than the influence range of

R

o

. Only when the surrounding rock temperature is greater than or equal to 250 ℃ can it cause the change response of the

R

o

values. The greater the thickness of diabase bed

the greater the influence range on

R

o

of organic matter in host rock

and the greater the increase of

R

o

near the bedrock. The influence range of diabase bed on

R

o

of organic matter in host rock is about the same to its own thickness.