
Continuing with the article on machine learning (ML), from the papers extracted in OnePetro, I have been able to detect the use of these ML algorithms:
- Neural Network 
- Genetic Algorithm 
- Support Vector Machine 
- Principal Component Analysis 
- Linear Regression 
- Fuzzy Logic 
- Hierarchical 
- K-Means 
- Singular Value Decomposition 
- Decision Tree 
- Support Vector Regression 
- Deep Learning 
- Logistic Regression 
- Boosting 
- Random Forest 
- Nearest Neighbor 
- Discriminant Analysis 
- Gaussian Mixture 
- Gaussian Process Regression 
- Naive Bayes 
- Hierarchical Clustering 
- Reinforcement Learning 
- K-Nearest Neighbor 
- Hidden Markov 
- C-Means 
- Fuzzy C-Means 
- Gaussian Mixture Model 
- Kernel Density Estimation 
- Gradient Boosting Tree 
- Kernel Approximation 
With a little bit of R magic:

From all these techniques, the top 20 most used are:

If you see I am forgetting a specific machine learning algorithm, please let me know.
Notes. (1) Fuzzy-Logic is not considered a ML technique; rather, belongs to control theory. But still, I am including it here because there is a considerable number of papers using the algorithm. (2) I grouped Convolutional Neural Networks with “Deep Learning”.
So, this is the state of use of machine learning in petroleum engineering.