GEOCHEMISTRY OF THE SOURCE ROCKS FROM JIUFOTANG FORMATION IN JD1 WELL, SOUTHWESTERN SONGLIAO BASIN

Through systematic evaluation on the organic geochemical and biomarker compound features of source rocks from Jiufotang Formation in JD1 well in Jinbaotun-Jargalang region of southwestern Songliao Basin, the authors conclude that the dark mudstone belongs to poor-medium grade source rocks with organic matter of II-type kerogen in low maturity-maturity stage. The n-alkanes are dominated by unimodal distribution of "front type" with main peak carbon numbers of C18 and C19. The odd-even predominance is not prominent. The Pr/Ph ratios(0.24-0.46) and gammacerane indexes (0.11-0.32) indicate the source rocks were formed under reduction condition with freshwater-brackish water lacustrine sedimentary environment. The distribution characteristics of C27-C28-C29 regular steranes are slightly various, reflecting mixed sources of organic matters. From the above, the source rocks in the study area have certain hydrocarbon generation potential.