# Investigation and Optimization of EOR Screening by Implementing Machine Learning Algorithms
## 2 Data Preparation
### Worldwide EOR Project Distributions  
The EOR project data is widely distributed. The data sources used in this paper mainly include the United States, Canada, China, and other countries because these countries have high oil demand. Petroleum is mainly distributed in the sedimentary rock layers in the upper crust. Sandstone and carbonatite are usually the main storage rocks for petroleum hydrocarbons. Other types of sedimentary rock layers may also become oil reservoirs. Figure 2 presents the distribution of reservoir lithologies and EOR types. As shown in Figure 2, only 35 project oil production reservoirs are distributed in other rock formations and the rest are distributed in sandstone and carbonatite reservoirs. EOR techniques are divided into three main categories: thermal oil recovery, gas flooding, and chemical flooding. Thermal oil recovery includes steam, combustion, and hot water; gas flooding includes nitrogen miscible flooding, nitrogen immiscible flooding, carbon dioxide miscible flooding, carbon dioxide immiscible flooding, hydrocarbon gas miscible flooding, and hydrocarbon gas immiscible flooding; and chemical flooding includes microbial flooding, surfactant flooding, and polymer flooding. Figure 2 also illustrates that 454 thermal projects  
Figure 1: Flow chart of worldwide EOR screening based on machine learning algorithms. has been successfully implemented, which has the highest occupation and account for 47.5% of worldwide EOR projects. Gas flooding has been conducted in 387 reservoirs and chemical flooding was used in 115 reservoirs, which occupies 40.5% and 12%, respectively. In addition, in the thermal method, the steam flooding technique is the most widely used; CO\({}_{2}\) miscible/immiscible flooding in gas flooding is a mature gas flooding technique, which is an important application of CO\({}_{2}\) and can reduce the content of CO\({}_{2}\) in the atmosphere; and among chemical methods, the polymer flooding technique is the most widely used. Based on the supplementary and complete initial dataset, a frequency distribution analysis of the eight parameters was conducted, as illustrated in Figure 3. The analysis reveals that porosity values for the projects in the dataset predominantly fall between 5% and 40%. The oil layer depth for production is mostly situated more than 100 ft underground, with a significant portion falling within the range of 0 to 12,500 ft. The permeability of the rock formations hosting oil ranges from 0 to 2000 millidarcies (md). Oil viscosity exhibits an uneven distribution, spanning from 0.04 centipoise (cp) to 10,000 cp; around 70% of the samples have a viscosity below 500 cp. The data points with a viscosity greater than 10,000 cp are not shown in the graph due to their limited occurrence. The dataset includes projects involving heavy crude oil and medium crude oil, as well as light crude oil and ultra-light crude oil. Oil temperature varies with depth, primarily falling within the range of 75 \({}^{\circ}\)F to 155 \({}^{\circ}\)F. The net thickness of the oil layer in the projects generally exceeds 3.4 ft, with most values below 200 ft, indicating a relatively thick and favorable rock formation. The initial oil saturation in the rock formations follows a normal distribution, with the 50% to 70% oil saturation representing the typical range and indicating a relatively high oil content. Figure 2: (**a**) Distribution of rock formations in the dataset. (**b**) EOR category distribution of the dataset. (**c**) EOR technique distribution of the dataset. A scatter plot matrix was utilized to reveal the relationships among reservoir/fluid parameters, as shown in Figure 4. It can be seen from the figure that there is a strong linear relationship between depth and temperature. The deeper the depth, the higher the temperature of the oil; the greater the gravity of the oil, the lower the viscosity; and the deeper the depth, the greater the gravity of the oil.