In the field of oil and gas exploration and development, the quick identification of reservoir crude oil properties has a guiding significance for engineers and technicians. Geochemical logging technology is a conventional method to evaluate the properties of crude oil in reservoirs, and it can provide professional knowledge for comprehensive evaluation of reservoirs. In this study, the principles of rock pyrolysis and gas chromatographic analyses in geochemical logging are studied. Moreover, a new method for quantitative analysis of crude oil density by chromatogram is proposed. Combined with the division standard of crude oil property density, the properties of reservoir crude oil can be quickly evaluated. In the experiment, first, the chromatogram was standardized and normalized using computer image processing software. The curve characteristic law of rock pyrolysis gas chromatogram was analyzed, and the corresponding characteristic parameter extraction method was proposed. The chromatogram was converted into a characteristic parameter matrix. Second, three types of artificial intelligence prediction and classification models were studied. The latest meta-heuristic optimization algorithm (sparrow search optimization algorithm) was used to optimize the hyperparameters of the generalized regression neural network, and the accuracy and convergence speed of the model were improved. To study the influence of different positions of rock samples on the experimental results, two groups of samples were utilized: cuttings samples and wall core samples. Based on a comprehensive comparison of the prediction results of the three models, it was found that the generalized regression neural network prediction model optimized by sparrow search algorithm provided the best effect, being a stable model, with small prediction density error, and strong generalization ability. The prediction error coincidence rate (absolute error < 0.02) of this model for cuttings and wall core samples was 95% and 100%, respectively. The root mean square errors were 0.0079 and 0.0069 respectively. The classification accuracy of crude oil properties was 95%. The analysis of the two groups of parallel experimental data indicated that the rock samples from the wall center can more accurately reflect the crude oil properties of the reservoir. Therefore, the method proposed in this study can provide reliable data support for reservoir comprehensive evaluation and on-site construction.
在油气勘探开发领域,快速识别储集层原油性质对于工程技术人员有非常重要的指导意义。地球化学录井技术是用于判断储集层原油性质的常规手段,能为储集层综合评价提供专业认识。该文研究了地化录井中的岩石热解分析和气相色谱分析的原理,提出了一种利用色谱谱图对原油密度进行定量分析的新方法,再结合原油性质密度划分标准,可快速判断储集层原油性质。首先使用计算机图像处理软件对色谱图进行标准化和归一化预处理,并分析了岩石热解气相色谱谱图的曲线特征规律,提出了岩石热解气相色谱谱图的特征参数提取方法,将色谱图转换为特征参数矩阵。其次,研究了3种人工智能预测分类模型,为了适合该实验对储集层原油密度的预测,对其做了部分优化改进,利用元启发式优化算法(麻雀搜索优化算法)对广义回归神经网络的超参数进行了优化,提高了模型的精度和收敛速度。最后,通过现场获得的气相色谱图样本对各模型进行训练并验证,综合对比3种模型预测的结果,发现基于麻雀搜索算法优化的广义回归神经网络预测模型效果最佳,模型稳定,预测密度误差小,可泛化能力强。该研究所提出的方法能为储集层的综合评价研究和现场施工提供可靠的数据支撑。
Keywords: crude oil density; gas chromatogram (GC); generalized regression neural network); sparrow search optimization algorithm.