Diabase intrusions in the 3rd member of Shahejie Fm in Xia 38 wellblock of Linpan oilfield

Jiyang depression

have very remarkable influences on maceral and vitrinite retlectance(R

o

)of source rocks above and below the intrusion

and the range of the effect is approximately equivalent to the thickness of the sill.The R

o

value within 10m around the sill is 1 to several times of that at normal geothermal field condition

and can even be as high as 3.44%. The intensity of thermal effect's impacts on the source rocks decrease progressively away from the sill

and tend to be normal geotemperature over 50m away form the sill.As a result of different diffusion and convection conditions

influences of the sill on overlying rocks are large in scope but low in intensity;while that on underlain rocks are small in scope but high in intensity.Hydrocarbons that have been generated rapidly under the influenee of magmatie thermal energy are mainly of medium-light hydrocarbons

while heaW hydrocarbons are obviously less.Such hydrocarbon distribution pattern is clearly different from that generated slowly in normal geothermal fields

whieh shows symmetrical distribution with balanced light and heavy hydrocarbons.Theoretical calculation shows that the thermal energy from magma might sufficiently cause the temperauure of source rocks nearby with a volume of 5 times that of the intrusion to rise 200℃.The real increase of temperature

however

might be smaller than the theoretieal calculation results.