摘要：
塔南凹陷烃源岩取芯资料少、有机非均质性强、成熟烃源岩不具备"三高一低"测井响应特征,针对此问题,采用变系数ΔlgR技术计算烃源岩TOC,通过将传统ΔlgR技术中的经验参数视为待定系数并采用实测TOC标定待定系数,其预测烃源岩TOC的平均误差为19.7%,比传统方法平均降低11.4%.依据实测TOC与氢指数(IH)的关系将烃源岩有机质丰度分差、中等、优质三级,对应的TOC界限分别为1%和2%.依据测井计算TOC曲线识别不同丰度级别烃源岩的厚度,通过井间插值落实不同丰度级别烃源岩的厚度分布.结果显示,差级别烃源岩厚度一般10~20 m,占南一段烃源岩总体积的21.5%;中等烃源岩厚度一般15~25 m,占烃源岩总体积的31.6%,优质烃源岩厚度一般20~30 m,占烃源岩总体积的46.9%.%In this paper,Total Organic Carbon (TOC)of source rocks in Nanyi section of Tanan sag was calculated using Variable-Coefficient ΔlgR model based on the classification evaluation of source rocks,and the volume ratio and plane distribution of source rocks at different TOC levels were discribed.Source rocks in Tanan sag were characterized by high natural gamma and interval transit time,but unlike the marine sources rokcs,the response of resistivity curve was weak. Therefore,using the Variable-CoefficientΔlgR model,taking the key coefficient in the model as variable and calculating the key coefficient in the model using the sampled data,the low accuracy resulted by the empirical parameter inΔlgR model was overcome.The results showed that TOC predicting error by variable-coefficientΔlgR models was 19.7%,which reduced about 11.4% compared toΔlgR model.According to the relationship between TOC and Hydrogen index(IH),sources rocks in Nanyi section were divided into three grades,including poor source rocks ,medium source rocks and excellent source rocks.According to TOC calculating results,the volume ratio and the plane distribution for each grade of source rocks were studied.Poor source rocks accounted for 21.5% of total source rocks in volume,and the general depth was 10~20 m.Medium source rocks accounted for 31.6%,and the general depth was 15~25 m.Excellent sources rocks accounted for 46.9%,and the general depth was 20~30 m.
