1. Fixed profit locking: Oil plants can estimate a reasonable profit level according to their own costs and market conditions, stipulate a fixed profit level in the contract, and then lock the expected profit by adjusting the base level according to the actual market conditions.

2. Hedging lock-in: Oil plants can hedge through financial instruments such as futures market or forward contracts, that is, operate long and short in the futures market at the same time to lock in the expected profit level.