鄂尔多斯盆地陇东地区长7段有效烃源岩及生排烃研究

通过烃源岩地球化学数据分析、测井有机碳计算、生烃潜力法及生排烃史模拟，研究了鄂尔多斯盆地陇东地区长7段有效烃源岩的分布、生排烃史及排烃强度。长7段有机碳含量大于1.0%的暗色泥岩（含油页岩）厚度主要为20~90 m，平均有机碳含量主要介于2%~9%，其有效烃源岩分布以w（TOC）=1.0%和R_o=0.7%为界限，具有大面积广覆式分布的特征；长7段有效烃源岩在侏罗纪末期开始成熟生烃，主要在早白垩世早期（140~130 Ma，R_o≈0.7%）开始排烃，至早白垩世末期（100 Ma）达到生排烃高峰（R_o≈1.0%），最大产油率接近400 mg/g，排油率达308 mg/g，晚白垩世以来的区域性构造抬升使得生烃停止；长7段有效烃源岩排烃强度主要分布于（10~250）×104 t/km2，具有强排烃特征，以长6—长8段致密油为主的延长组油藏主要分布于排烃强度大于20×104 t/km2的地区，油气具有近源短距离富集的特点。 

Active source rocks of Chang 7 member and hydrocarbon generation and expulsion characteristics in Longdong area,Ordos Basin

The distribution, hydrocarbon generation and expulsion history and intensity of active source rocks in the Chang 7 member of the Yanchang Formation in the Longdong area of the Ordos Basin were studied based on geoche-mical data, TOC calculation by well logging, hydrocarbon generation potential and expulsion history simulation. Dark mudstone (including oil shale) thickness with an organic carbon content (w(TOC)) more than 1.0% in the Chang 7 member mainly ranges from 20-90 m, and the average w(TOC) is mainly between 2%-9%. Active source rocks of the Chang 7 member have a w(TOC) value over 1.0% and R_o value over 0.7%, and are widely distributed in the Longdong area. They became mature and generated hydrocarbon at the end of Jurassic, expelled hydrocarbon during the early stage of the Early Cretaceous (140-130 Ma,R_o≈0.7%), and reached peak at the end of the Early Cretaceous (100 Ma, R_o≈1.0%). At this time, the oil generation ratio reached 400 mg/g TOC, and the oil expulsion ratio could be 308 mg/g TOC. But oil generation was forced to stop as a result of regional tectonic uplift since the Late Cretaceous. The oil expulsion intensity is mainly (10-250)×104 t/km2, showing the characteristics of strong oil expulsion. Oil reservoirs of the Yanchang Formation dominated with tight oil of the Chang 6-Chang 8 members mainly developed in the area with an oil expulsion intensity over 20×104 t/km2, which indicated that oil accumulation in tight sandstones has characteristics of being near the oil source with a short migration distance.