基于随机森林的页岩气“甜点”分类方法

doi:10.13809/j.cnki.cn32-1825/te.2023.03.011

摘要/Abstract

摘要：

为了解决页岩气“甜点”分类识别涉及指标多、需要根据个人经验判别、耗时耗力的问题，提出了一种基于随机森林模型的页岩气“甜点”分类方法。首先，选取长宁区的10口井数据，利用肯德尔相关分析筛选出用于识别的11种特征。然后再分别采用单棵决策树和随机森林方法进行预测，得到页岩气“甜点”识别结果。最后，对预测结果分类并进行算法参数优化。实际应用结果表明，单棵决策树预测精度虽可以达到97.7 %，但呈现过拟合趋势，且剪枝之后拟合精度大大降低到只有70.7 %；采用的随机森林方法避免了单棵决策树的缺陷，并且预测的精度达到98 %，而且，计算代价小，能有效降低时间损耗、节省人力成本。证明随机森林机器学习方法结合多源信息是实现页岩气“甜点”识别预测的一种有效手段。

关键词: 页岩气, “甜点”, 机器学习, 决策树, 随机森林

Abstract:

The classification and identification of shale gas “sweet spot” involves a variety of different factors, which requires personal experience, and is usually time and resources consuming. In order to solve this problem, an efficient and effective classification and identification method for shale gas “sweet spot” based on the Random Forest method is proposed. Firstly, data from ten wells in Changning area are selected and eleven features are selected for “sweet spot” classification by the Kendall correlation. Then, the single decision tree and the Random Forest method are used for the “sweet spot” classification and identification. Finally, the results are verified and the Random Forest parameters are optimized. The experimental results show that although the prediction accuracy of a single decision tree can reach 97.7 %, it shows a trend of overfitting, and the fitting accuracy is greatly reduced by only 70.7 % after pruning. The Random Forest method avoids the disadvantage of the single decision tree method, and the prediction accuracy reaches 98 %. Moreover, the computational cost is low, which can effectively reduce the time loss and save the labor cost. As a result, the proposed Random Forest machine learning method with multi-source information is an effective shale gas “sweet spot” classification and identification method.

Key words: shale gas, “sweet spot”, machine learning, decision tree, Random Forest

中图分类号:

TE132

聂云丽, 高国忠. 基于随机森林的页岩气“甜点”分类方法[J]. 油气藏评价与开发, 2023, 13(3): 358-367.

NIE Yunli, GAO Guozhong. Classification of shale gas “sweet spot” based on Random Forest machine learning[J]. Petroleum Reservoir Evaluation and Development, 2023, 13(3): 358-367.

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类型		有机质质量			储层品质		完井质量
类型		TOC/ %	总含气量（压力系数为1.0）/ （m³/t）	总含气量（压力系数为2.0）/ （m³/t）	孔隙度/ %	厚度/ m	泊松比	杨氏模量/ GPa	垂向应力/ MPa	破裂压力/ MPa	脆性矿物含量（含碳酸盐岩+碎屑岩）/%	脆性矿物含量（纵横波比）/%
Ⅰ	最小值	2.30	0.90	1.30	2.70	3.0	0.190	31.1	50.10	43.90	43.00	42.80
	平均值	7.25	4.60	6.80	5.00	735.0	0.240	25 444.4	81.30	91.20	62.80	65.35
	最大值	12.20	8.30	12.30	7.30	1 467.0	0.290	50 857.7	112.50	138.50	82.60	87.90
Ⅱ	最小值	1.70	2.30	3.50	3.20	11.0	0.150	36.2	54.10	40.60	46.60	42.10
	平均值	3.05	3.95	5.75	4.60	474.0	0.225	25 519.2	83.35	94.50	63.15	61.45
	最大值	4.40	5.60	8.00	6.00	937.0	0.300	51 002.3	112.60	148.40	79.70	80.80
Ⅲ	最小值	1.00	1.30	2.00	0.30	7.0	0.240	38.6	51.80	46.70	48.40	61.50
	平均值	2.85	1.50	4.30	1.45	177.9	0.290	31 901.2	82.25	110.65	55.55	75.00
	最大值	4.70	1.70	6.60	2.60	348.8	0.340	63 763.9	112.70	174.60	62.70	88.50

模型	甜点类型	precision （精确率）	recall （召回率）	f1-score （f1评分）	support （支持度）
决策树	Ⅰ型	1.00	0.96	0.98	122
	Ⅱ型	0.91	1.00	0.95	49
	Ⅲ型	1.00	1.00	1.00	16
随机森林	Ⅰ型	0.97	1.00	0.98	118
	Ⅱ型	1.00	0.92	0.96	53
	Ⅲ型	1.00	1.00	1.00	16