User Management - Multiple Projects

My account has hundreds of projects,
How do I find all the projects where member X is part of? How do I delete the access of member X without going through hundreds of projects to find this out.

for deleting any user access you have an option of gitlab GUI where you can login with member x and remove its access on that project. all assigned project for that member will be listed on project list . go to its members page from where you can delete its access.