@BRAHMESH@ that doesn't seem easy to do. You would have to instrument each thread to include additional fields in the LogContext, keeping in mind that not all threads are currently simply populating the userId from the Requestor and there's no obvious extension point to plug this.
Maybe you can start using the internal id in Pega for the OperatorID? This way you don't need to update the log format and internal id is also used everywhere in Pega admin screens, increasing your security.
Also maybe good to consider using JSON appender and processing the log entries downstream. Another point is that you have tagged the question with very old Pega version. Given the topic at hand, maybe recommend your client to work on upgrading first.