Influence of Abnormal Geothermal on HydrocarbonGeneration: Case study on the diabase intrusion of the Santanghu Basin

Key words: 
• diabase /
• abnormal geothermal /
• hydrocarbongenerating /
• maturation

Abstract: In order to probe into abnormal geothermal's influence on hydrocarbongeneration, we collected eight source rock samples (W008W015) from the black mudstone series of strata of Carboniferous upper Haerjiawu group on the south side of the diabase intrusion of the East Daheishan Profile in the Santanghu Basin, whose distance to the diabase rock is 20 cm, 50 cm, 100 cm, 180 cm, 300 cm, 500 cm, 1 000 cm, and 1 700 cm, respectively. Through analysis of the basic geochemical characteristics such as the atomic ratios of Ro to H/C and to O/C, the change of the chloroform bitumen "A" and total hydrocarbon of the eight samples, along with selective analysis of the chromatographic characteristics of the saturated hydrocarbon of five of them, we found that with the distance to the diabase rock greater than 180 cm, the content of Ro remains almost unchanged, however, the content of Ro significantly increases with the distance less than 180 cm; the atomic ratio of H/C in W008 and W009 is relatively small, which is 0.385 and 0.404, while from W011 to W015, the atomic ratio of H/C is about 0.5, which remains the same on the whole; the range of variation in the atomic ratio of O/C is relatively small concentrating around 0.1, and the atomic ratio of O/C in W008 and W009 is slightly smaller than adjacent samples (W010, W011); the chloroform bitumen "A" and total hydrocarbon of W008 is slightly higher than that of W009 ~ W012; from the pespective of organic saturated hydrocarbon parameters, CPI in W008, W009 and W010 is relatively small, which is obviously different from that of in W012, and W014. From the above analysis, we can conclude that the overall maturity of this source rock is rather high, and near the diabase intrusion with the distance range of 1~1.8 m, its maturity index has the trend of exceptional increase which shows the source rocks directly exposed to the intrusive rocks has a relative smaller scope of baking effect which is less than about 1.8 m.