渤中凹陷西南部烃源岩TOC含量预测

Prediction of TOC content in source rocks in southwestern Bozhong Sag

烃源岩总有机碳(TOC)含量是评价有机质丰度的主要指标。地球化学方法的岩心测试仅能获得离散的TOC含量数据,难以实现烃源岩的三维定量评价。结合地球物理测井方法和地震叠前反演方法,针对渤中凹陷西南部陆相深层烃源岩,通过岩石物理交会分析优选对TOC含量敏感的弹性参数,建立TOC含量与纵波速度、密度的地震反演模型;使用拓展ΔlogR方法和地震叠前反演方法分层计算渤中凹陷西南部东营组和沙河街组烃源岩TOC含量,获得TOC含量曲线和TOC含量三维反演体,进而计算东二下段、东三段、沙一二段、沙三段烃源岩TOC含量地震预测平面图。结果表明预测误差较小,证明了该方法的可靠性。研究区烃源岩非均质性较强,总体呈现"层系多、分布广"的特征。东营组烃源岩北部优于南部,且东三段TOC含量值总体高于东二下段;沙河街组TOC含量值整体较高,为研究区的主力烃源岩层,TOC含量呈现自沉积中心向外逐渐降低的趋势,尤以沙一二段A、B、C、E井区及其附近区域、沙三段A、C井区及其西部、南部部分地区TOC含量值最高,具有良好的生烃潜力。

The total organic carbon(TOC)content in source rocks is the primary parameter for evaluating the abundance of organic matter.Core measurement by geochemical methods can only obtain discrete TOC,and it is difficult to achieve three-dimensional quantitative evaluation on source rocks.In this study,combining geophysical logging data with seismic pre-stack inversion,and aiming at the deep continental source rocks in the southwestern Bozhong Sag,we analyzed and optimized the elastic parameters sensitive to TOC through petrophysical intersection diagrams and established a seismic inversion model of TOC and P wave velocity and density.Using the optimized extendedΔlogR method and seismic pre-stack inversion method,we calculated the TOC of the Dongying and Shahejie formations in the southwestern part of the Bozhong Sag.Finally,we obtained a TOC curve and a 3 DTOC inversion body,and calculated the TOC seismic prediction plans of the E3 d2 L,E3 d3,E2 s1+2 and E2 s3 members.The results show that the well-seismic prediction error is small,proving the reliability of the prediction method.The source rock in the study area is highly heterogeneous,and characterized by"multiple layers and wide distribution".The source rocks in the northern Dongying formation are better than those in the southern,and the TOC of the E3 d3 is generally higher than the E3 d2 L.The Shahejie formation has higher TOC,and it is the primary source rock interval in the study area,showing gradually decreasing TOC outward from the depositional centers,especially in Wells A,B,C and E drilled into the E2 s1+2 and their nearby areas.In Wells A and C drilled into the E2 s3,and their west and south,the TOC is the highest,showing agood hydrocarbon generating potential.