We put about a quart of bleach in our well once a year. In a drilled well, you need to be real careful on pouring it on wires, pipes, etc in your well.Don't people drop chlorine tabs down their wells?...I thought I heard that
In our drilled well, I drilled a hole through the wall of the pipe and connected a PVC elbow with a screw on cap and extended to PVC down past the well internals so bleach does not come on contact with anything except PVC or water. With the screw on cap outside of the pipe, it is not really secure from tampering but we don't have anyone around to tamper with stuff.
I am sure there is some way to secure it if needed.