Thank you for your question.  The snake in your photographs is a northern watersnake (Nerodia sipedon).  It is a non-venomous species.  This species is heavy-bodied and known for its variability in body pattern and color.  They can reach a maximum length of approximately 50 inches, but typical length is 2 - 3 feet.
This snake is normally found in or in the vicinity of water.  It lives in creeks and streams, ponds, lakes, rivers, swamps and wetlands.  However, they can sometimes be found several hundred feet from water traveling to hibernation areas or to other aquatic habitats.  If not in the water, they are often seen basking in trees or shrubs in or hanging over the water, from which they immediately drop in the water if they feel threatened.  
This species feeds primarily on fish and amphibians, but will also eat invertebrates such as insects and leeches.
When threatened, water snakes always try to escape as their first response.  If cornered, they flatten their head and front part of the their body to make themselves look larger and more intimidating.  They will also strike out in an effort to discourage any further attention.  If you pick one up, they normally bite, often repeatedly, twist their body in an attempt to get out of your grip, and expel strong-smelling musk from their anal glands.
If this snake is still in your crawlspace well, place a branch or small log down in the well, and the snake should use it to escape from the well.
Hope this answers your question, and thanks for using Ask an Expert.

Jim

Thanks. . I'll find a branch to let him get out. He is still there.

No problem. Contact us anytime.

Jim