基于广义ΔlgR技术的致密气源岩有机碳测井评价

Evaluation of Organic Carbon Logging of Tight Gas Source Rocks Based on Generalized-ΔlgR Technology

松辽盆地X地区的烃源岩评价主要基于岩心资料开展,受烃源岩非均质性强和岩心(屑)测试样品有限的双重制约,通过样品实测总有机碳质量分数(w (TOC))平均值粗略表征烃源岩有机质丰度的方法已经无法满足油气精细勘探的需求。结合w (TOC)实测数据和测井曲线,针对研究区陆相烃源岩埋深大、孔隙度和电阻率曲线对有机质响应的敏感性差的特点,利用广义ΔlgR技术评价该区烃源岩,通过实测w (TOC)标定模型内的待定系数,建立针对研究区的w (TOC)预测公式,并对全区35口井进行w (TOC)测井评价,依据测井评价的结果落实层序格架内烃源岩w (TOC)的分布特征。结果表明,广义ΔlgR技术预测w (TOC)与实测w (TOC)的平均相对误差不超过20.1%,结果比较可靠。研究区发育2个w (TOC)分布的高值区,富w (TOC)的暗色泥岩在空间上集中发育在三级层序SQ4中上部和SQ3中部,w (TOC)平均值分别为3.1%和2.4%。

Source rocks evaluation in X Area of Songliao Basin was based on core data,because of the dual constraints of strong heterogeneity of source rock and limited core(cuttings)test samples,the method of representing the abundance of organic matter in source rock by the w(TOC)average of total organic carbon fraction measured by the sample can no longer meet the needs of fine oil and gas exploration.Based on the tested w(TOC)value and the logging curves,Generalized-ΔlgRtechnology was applied to calculate the w(TOC)in view of the large buried depth of continental source rocks and the poor sensitivity of porosity and resistivity curves to the response of organic matter in the study area.Based on the undetermined coefficients measured in the w(TOC)calibration model,the w(TOC)prediction formula is established for the study area,and the w(TOC)logging evaluation of 35 wells is carried out in the whole area.The w(TOC)distributive characteristics of the source rock in the sequence stratigraphic framework are determined based on the logging evaluation result.In the study area,there are two high value areas of w(TOC)distribution.The w(TOC)rich dark mudstones are concentrated in the middle and upper parts of the tertiary sequence SQ4 and SQ3,the average w(TOC)are 3.1% and 2.4% respectively.