From what I can see from your photos, I think what I am seeing is a single pipe pitless adapter. There is a part of the adapter that has the pipe hung all the way down to the pump, and that can be mated and separated from the pipe that leaves the well casing back to your house. From what you have posted and the discussion that followed, I am going to guess you have a simple 2 part interference-fit pitless adapter with an o-ring or other type of gasket. If your pitless adapter used a rubber or epdm gasket, they fail over time, just as reach4 mentioned. In the northeast US its a very common service call. There is stuff in the water that contributes to electrochemical degradation, and its by the same physics radiator hoses and belts on cars need to be periodically changed. They rot over time, just because the material they are made of decomposes.
If you look at my avatar photo, that is the pump side of a 1970s-era Campbell pitless adapter. It takes a leather o-ring, and that o-ring if made properly and of good components and workmanship can be expected to last about 8 years. The original that was installed lasted 30 years, but nothing is made to last 30 years anymore, no matter where you get it.
Maybe concrete mix will last that long, but that's another thread.
OH By the way, these things are called "pitless adapters" because their ingenious yet basic design eliminated the need for a maintenance pit dug next to the well casing. The vertical (upNdown) to horizontal (leftyrighty) connection is possible using a pitless adapter because it can be manipulated from one point.
I see safety rope in your photo. That gets me to think that your pump is 300 feet down or less. Beyond 300 feet the local driller guys say to hell with the safety rope, if its broken loose beyond 300 feet forget looking for it.
Ok back to the adapter. If your setup is like hundreds or thousands on the east coast, then you will have the following:
1. A deep hole dug in to the ground and well casing inserted.
2. A pump that lives at 75% or greater of the total depth of the above mentioned hole.
3. Plumbing: PVC or flexible tubing (poly pipe) that comes from the top of the pump all the way to the adapter headed up here to the surface of planet earth, which is probably about 4 feet from the ground level where the well cap lives. If you live somewhere that never gets cold weather, the pitless connection even closer to the ground surface level.
4. A pitless adapter that helps all that tubing coming from the pump make the 90 degree turn to get water to your house. At that "pitless" connection, the pump and all its piping can be in some way or another disconnected from the inside of your well casing so that you may bring up the pump, safety rope, wiring, tubing all the way up to ground level to make repairs or replace things.
I was able to change my pump, replace the wiring, and make my pitless adapter stop leaking by watching YouTube videos. But I must warn you- I was EXTREMELY lucky. There is no warning on any youtube video that says "this video was made by an idiot." Since all you need to post a howto video on Youtube is a phone or computer and a dumb idea, any one can do it.
so if you want to attack this on your own, i will tell you the pros and cons of calling up a pump person who might have been a con at one time that frequented pros.
pros of fixing it yourself:
you may have an issue that costs less than $50 in parts, i.e. $8 gasket or o-ring and $50-$8 the rest spent in making a 1-inch black pipe home made pitless puller t-tool. Assuming your time has no monetary worth, you could spend a saturday pulling the pitless apart with a home made t - tool and hope you mate a new gasket or o-ring into your adapter and seat it properly.
assuming you get this all correct, you may have saved hundreds on a $50 or less repair.
the cons of doing it yourself-
if you watch enough videos and get brave enough to go to home depot, buy black pipe and fashion it into a t shaped pitless puller, it just might work. OR, you could find out that once you broke the pitless loose that that the pump was only at the top of the water of a 750 foot well and it was a 3 horsepower unit so it weighed about 300 pounds which is way more mass pulled by gravity, and you dropped it or it broke loose and now it is on its way sailing through the earth to china. Lost pump in a shallow well= exspensive to remedy. lost pump in a very very deep well that is always full of water because the driller pierced an everstrong aquifer= what lost pump? Who cares, No pump here, sending a new one down there. Supposing all goes well (no pun intended) with your breaking your pump and poly pipe via pitless connector loose from holding that weight and putting it on YOU and your buddy (hold my beer), THEN...there is the situation that you just might not be able to properly pack the o ring or gasket because of what is gunked up around it to make a good seal, and you cant get it back in. You are still stuck even though you were so good at manipulating that heavy setup.
I did all this work myself and learned these things:
Pulling a pump that is 200 feet down a 250 deep 5 inch bore with 194 feet of 1 inch header poly gives a 46 year old like me an umbilical hernia. Its only 200 feet of yanking straight up but, holy crap, it seemed like the poly pipe would reach the eye of God when you are humping it out of that bore before it ended. You will probably need to pull up less than 8 feet of this contraption to work on it.
If you do it yourself and it works perfectly, you are the grand supreme winner.
If you have to call a well company because you started it on your own but ran into problems and now you called them instead of calling them first, you will likely be very lucky if they charge you less than DOUBLE what they would have if you called them in the first place instead of trying it on your own.
Your mileage may vary. I always encourage people to take the do it yourself route. In this case I wrote a very long post that tells you that you might me making a cheap (under $500) service call cost many thousands. I did it successfully myself, but I am crazy and was extremely lucky.
I invite reach4 and valveman to correct any technical mistakes in my advice to you. They know lots more about this than I do.