There's no standardized term or formula for "Team Leader" specifically used in Oil & Gas terminology. The concept of a team leader is a general management practice and its application in Oil & Gas depends on the specific team and its functions.

However, if you're looking for metrics related to workforce management in the Oil & Gas industry, here are some relevant concepts:

1. Crew Size: This is a fundamental metric, representing the number of personnel assigned to a specific operation or project. It can be calculated as:

Crew Size = Number of Workers + Number of Supervisors + Number of Team Leaders

2. Labor Productivity: This metric measures the efficiency of the workforce in terms of output per unit of labor input. It can be calculated as:

Labor Productivity = Total Output / Total Labor Hours

3. Labor Cost: This represents the total expenses related to labor, including wages, benefits, and training. It can be calculated as:

Labor Cost = (Hourly Wage * Number of Hours Worked) + Benefits + Training Costs

4. Staffing Ratio: This metric compares the number of supervisors and team leaders to the total number of workers. It can be calculated as:

Staffing Ratio = (Number of Supervisors + Number of Team Leaders) / Number of Workers

5. Workforce Turnover: This metric reflects the rate at which employees leave the company, which can be a significant factor in operational efficiency. It can be calculated as:

Workforce Turnover Rate = (Number of Employees Leaving / Average Number of Employees) * 100

Important Note: The specific formulas and metrics used for workforce management in the Oil & Gas industry will vary depending on the company, project, and operational context. It's essential to consider the specific needs and objectives of your organization when calculating and interpreting these metrics.