Coordinated and efficient prediction of multiple parameters for complex shale reservoirs based on deep learning: A case study of Qingshankou Formation in Songliao Basin
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摘要:目的
松辽盆地青山口组是我国陆相页岩油重点勘探层系,但该套页岩储层非均质性强、岩性复杂,同时研究区存在岩心实验样本有限、核磁共振测井资料稀缺的现实约束,传统储层评价方法存在精度有限、区域适用性较差的问题;纯数据驱动机器学习又容易受样本数量制约,泛化能力难以保障。针对上述矛盾,本文提出一套融合地质先验知识与机器学习的多参数协同预测方法,实现页岩储层关键参数的测井定量评价。
方法构建由改进 Δlog
R 法、轻量化全连接神经网络(FCNN)和岩心标定优化经验公式共同组成一体化预测框架,完成总有机碳质量分数w (TOC)、矿物含量与孔隙度的协同高精度反演。改进 ΔlogR 法引入分段地层基线校正与优化权重系数D 动态调整策略,适配高成熟度页岩的非线性测井响应;轻量化 FCNN 以声波时差(AC)、伽马射线(GR)、井径(CAL)、补偿中子(CNL)、深侧向电阻率对数(logLLD)、自然电位(SP)、补偿密度(DEN)共 7 条常规测井曲线为输入,建立硅质、黏土和碳酸盐3类主要矿物含量的非线性反演模型;孔隙度预测基于岩心实测数据标定,优化声波–密度–中子协同计算式,改善超低孔页岩储层的预测精度。结果实例盲井验证表明:改进 Δlog
R 法将w (TOC)预测决定系数R 2由 0.613 提升至 0.786;矿物含量预测模型平均R 2达 0.867,在小样本条件下依然具备良好泛化能力;孔隙度预测R 2由 0.68 提升至 0.91。结论该套预测框架充分兼顾地质合理性与物理可解释性,有效化解小样本条件下模型泛化不足的难题,显著提升复杂页岩储层多参数预测的精度与稳定性,建立了适用于小样本非常规储层的一体化测井解释体系,可为松辽盆地及国内外同类陆相盆地页岩油储层甜点识别、可压裂性评价与高效开发提供技术支撑。
Abstract:ObjectiveThe Upper Cretaceous Qingshankou Formation of the Songliao Basin represents a critical exploration target for continental shale oil in China. Nevertheless, this shale reservoir is characterized by strong reservoir heterogeneity and complex lithological assemblages. Practical exploration is further constrained by limited core test samples and scarce nuclear magnetic resonance (NMR) logging data in the study area. Conventional reservoir evaluation approaches suffer from limited prediction accuracy and poor regional adaptability. Meanwhile, purely data-driven machine learning models frequently suffer from deteriorated generalization ability when training datasets are insufficient. To resolve these bottlenecks, this study develops a multi-parameter coordinated prediction method integrating geological prior knowledge and machine learning algorithms for quantitative well-log evaluation of key shale reservoir parameters.
MethodsAn integrated prediction framework was constructed by combining an improved Δlog
R method, a lightweight fully connected neural network (FCNN), and core-calibrated optimized empirical formulas to achieve high-precision coordinated inversion of total organic carbon mass fractionw (TOC), three major mineral components, and total porosity. The improved ΔlogR algorithm adopted segmented stratigraphic baseline calibration and dynamically adjustable weighting coefficientD , which mitigated the limitations of fixed-baseline linear assumptions and adapted to nonlinear logging responses within high-maturity shale intervals. The lightweight FCNN took seven conventional well-logging curves as input variables: acoustic travel time (AC), gamma ray (GR), caliper (CAL), compensated neutron log (CNL), logarithmic deep lateral resistivity (logLLD), spontaneous potential (SP), and compensated density (DEN). It established a nonlinear inversion model for felsic, clay, and carbonate mineral contents. For porosity estimation, an acoustic-density-neutron synergistic calculation formula was optimized using core-measured porosity data. It substantially enhanced the prediction accuracy for ultra-low-porosity shale reservoirs.ResultsBlind-well validation demonstrated that the improved Δlog
R method increased the coefficient of determinationR 2 ofw (TOC) prediction from 0.613 to 0.786. The lightweight FCNN mineral prediction model yielded an averageR 2 of 0.867 and maintained favorable generalization ability under small-sample conditions. After formula optimization, theR 2 of porosity prediction increased from 0.68 to 0.91.ConclusionThe proposed prediction workflow balances geological rationality and physical interpretability and effectively alleviates the problem of insufficient model generalization caused by limited training samples. It remarkably improves prediction accuracy and stability for multi-parameter inversion in complex shale reservoirs and forms an integrated well-log interpretation system applicable to small-sample unconventional reservoirs. This study can provide reliable technical support for “sweet spot” identification, fracability assessment, and efficient development of shale oil reservoirs in the Songliao Basin and other similar continental basins worldwide.
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图 1 松辽盆地构造平面图[24] (a) 与地层层序表 (b)
Figure 1. Tectonic map (a) and stratigraphic column (b) of Songliao Basin
表 1 研究区数据资料统计
Table 1. Data statistics of study area
数据类型 数量 岩心数据 X 射线衍射(XRD) 324块 总有机碳质量分数w(TOC) 1286 块镜质体反射率Ro 861块 测井数据 自然电位SP 1023 口井自然伽马GR 1026 口井声波时差AC 1026 口井补偿中子CNL 628口井 补偿密度DEN 1024 口井深侧向电阻率LLD 1021 口井表 2 改进的ΔlogR法中使用的参数
Table 2. Parameters used in improved ΔlogR method
地层 基线电阻率/(Ω·m) 基线声波时差/(μs·ft−1) 优化权重系数D 青一段 4.5 80 0.42 青二段 6.0 76 0.47 青三段 7.2 85 0.51 -
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