Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (3): 317-322.doi: 10.11743/ogg20050309

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Influences of thermal effect of diabase intrusion on hydrocarbon generation in Xia 38 wellblock Linpan oilfield

Cao Xuewei1, Hu Wenxuan1, Jin Zhijun2, Zhu Dongya1   

  1. 1. Department of Earth Sciences, Nanjing University, Nanjing, Jiangsu;
    2. Exploration and Production Research Institute, SINOPEC, Beijing
  • Received:2005-03-12 Online:2005-06-25 Published:2012-01-16

Abstract:

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(Ro)of source rocks above and below the intrusion,and the range of the effect is approximately equivalent to the thickness of the sill.The Ro 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.

Key words: thermal effect, vitrinite reflectance (Ro), characteristics of soluble hydrocarbons, diabase sill, source rocks, Linpan oilfield

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