My question will show that I know nothing about geothermal. I have an old 25' deep 4.5' diameter brick lined water well near where I plan to build a new high efficiency house, near Victoria, British Columbia. Is there any point to investigating this further? Is the volume of the well sufficient to provide some heat to a passive house? Thanks

Could be. It depends on if the well will make enough flow. If it will make 8-10 GPM you can do a lot with an open loop system. Probably need to drop in a pump and do a long term test.