In the oil and gas industry, "tie" can refer to a few different things, depending on the context. Here are a few possibilities:

1. Tie-in: This is the most common meaning. It refers to the process of connecting a new piece of equipment or pipeline to an existing system. This can involve welding, bolting, or other methods of joining the two components.

2. Tie-back: This refers to the process of connecting a new well or production facility to an existing pipeline or processing facility. This is often used when developing new fields or expanding existing production.

3. Tie-in point: This is a specific location on an existing pipeline or equipment where a new connection can be made.

4. Tie-in diagram: This is a drawing that shows the location of tie-in points and how new equipment will be connected to the existing system.

5. Tie-in crew: A team of workers responsible for completing the tie-in process.

6. Tie-in schedule: A timeline outlining the steps involved in the tie-in process.

The specific meaning of "tie" will depend on the context of the discussion. If you can provide more context, I can give you a more specific answer.