基于测井参数的煤系烃源岩总有机碳含量预测模型

Prediction model of total organic carbon content on hydrocarbon source rocks in coal measures based on geophysical well logging

  • 摘要: 复杂沉积环境下,烃源岩物性差异较大。经相关性分析揭示了煤系烃源岩TOC含量与各测井参数间存在相关性差异较大、各测井参数间含有互相关关系的特点。采用平均影响值(MIV)方法对测井参数进行筛选,筛选后的测井参数进入最终的BP神经网络建模,从而有效地规避了测井信息间的非相互独立性导致的模型预测误差增大及建模时间增加。依据研究区实验分析的TOC含量数据,分别建立适用于煤系烃源岩的Δlog R,BP神经网络和遗传算法(GA)优化的BP神经网络TOC含量预测模型。对模型试算分析,结果表明:GA改进后的BP神经网络模型预测效果最好,稳定性强,受烃源岩非均质性影响程度小,可以精细地反映煤系烃源岩TOC含量的细微变化。

     

    Abstract: Hydrocarbon source rocks have large physical property differences because of their complicated sedimentary environments. According to the correlation analysis between the TOC and the logging parameters,it has been found that the source rocks in coal measures has the characteristics of marked correlation difference between the TOC and the logging parameters,and the logging parameters exist a cross correlation. To begin with,the logging parameters which selected by using the mean impact value method will participate in the final BP neural network modeling. Thus,the predication error of the model and the adding modeling time caused by non-interdependence between logging parame- ters are effectively avoided. In addition,the prediction models which called Δlog R model,BP neural network model and improved BP neural network with genetic algorithm model are established based on the determined TOC data for calculating the organic carbon content of source rocks in coal measures. Finally,the modeling computation and error a- nalysis for the three kinds of models are conducted. Results show that the improved BP neural network with genetic al- gorithm model has the best prediction results with strong stability and high precision,and it is hardly affected by the heterogeneity of source rocks. Therefore,it can perfectly reflect the subtle changes of TOC content on hydrocarbon source rocks in coal measures.

     

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