Abstract: Source rocks evaluation is of great importance for gas exploration in Changling depression of southern Songliao basin. Aimed to make clear the TOC distribution of source rocks in Shahezi formation, based on the logging data and core tested data, variable coefficient ΔlgR model was used to calculate the TOC quantitatively, source rocks of different TOC grade and their thickness distribution were described. The key coefficients in the model were calculated using variable coefficient ΔlgR model according to the sampled data of the studied area, and TOC calculation results can reflect the TOC underground accurately. TOC predicting error by variable coefficient ΔlgR model was about 19.1%, which was reduced 17.5% compared to traditional ΔlgR model. Source rocks in Changling depression are characterized by high TOC value, middle less source rocks, good source rocks and excellent source rocks account for 26.1%, 18.2% and 55.7% of all the source rocks in volume, respectively. Good and excellent source rocks mainly distributed in Heidimiao sag, the maximum thickness is over 400 meters, Haerjin and Qianbei sags also developed good source rocks the general thickness is 200~300 meters.

Key words: Source rocks, TOC, Logging, Improvement, ΔlgR, Changling depression, Songliao basin

摘要： 精细评价长岭地区烃源岩发育特征对提高该区探井的成功率具有积极意义。以常规测井曲线和实测TOC数据为基础,采用改进的ΔlgR 技术,通过岩心测试TOC值刻度测井解释模型的待定系数,建立了长岭断陷烃源岩TOC含量定量解释公式,刻画了不同TOC含量烃源岩的平面分布。改进的ΔlgR 技术对该区TOC的预测误差为19.1%,比传统方法降低17.5%,计算结果真实地反应了地下TOC的分布。结果表明,该区烃源岩TOC含量较高,中等以下丰度级别占烃源岩总量的26.1%,好丰度级别占烃源岩总量的18.2%,很好丰度级别占烃源岩总量的55.7%。好级别以上烃源岩主要分布在黑帝庙次洼,厚度最大超过400m,其次是哈尔金次洼和乾北次洼,厚度一般为200~300m。

关键词: 烃源岩, 有机碳, 测井, 改进, ΔlgR, 长岭断陷, 松辽盆地