鄂尔多斯盆地陇东地区长7段有效烃源岩及生排烃研究

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

郭凯

Guo Kai

中国石油 长城钻探工程有限公司 解释研究中心, 北京 100101 2. 中国石油大学 油气资源与探测国家重点实验室, 北京 102249

Geoscience Centre, CNPC Greatwall Drilling Company, Beijing 100101, China 2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China

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Ro=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，Ro≈0.7%）开始排烃，至早白垩世末期（100 Ma）达到生排烃高峰（Ro≈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。

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 Ro 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,Ro≈0.7%), and reached peak at the end of the Early Cretaceous (100 Ma, Ro≈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.

国家自然科学基金重点项目“致密砂岩微米—纳米级孔喉网络系统石油充注、运移和聚集机理”（41330319）资助。

https://doi.org/10.11781/sysydz201701015