Question

you need to share fairly complicated information about an ongoing work project with just one co worker which genre would be most appropriate for this writing task

Answer 1

The most appropriate would be to send an email to your co-worker, clearly, succinctly and objectively detailing each complicated project work information. That way you keep impersonal communication with your co-worker, let you know about the project, and keep you up to date on the complications the project is having or may have.