Sometimes you drill an oil well expecting to strike it rich. Other times, you get oil, but it is not enough to fill a couple of barrels. The rest of the time you make a nice profit for a while, but the well dries up. In fact, wells drying up is exactly what they are supposed to do because the pocket of oil you struck is just that; a pocket. It is not an endless supply of oil that just keeps flowing into the well an up the pipeline. The oil will run out, and when it does, you will need to close it for good. If you have never closed a well before, here are some things you will need and a few things you will need to do to get that well closed.
This is a rig that allows you to "workover" the oil well to remove equipment and close the well completely. Sometimes you can use a workover rig just to change oil well pipeline equipment or slow the pumping process down so that none of the remaining oil in the well is accidentally wasted from being pumped out too fast. In your case, you are closing the well and removing all of the equipment, which means that you need a workover rig to take everything out of the well and fill the hole in with dirt.
If you remember back to the days when you put all of the pipelines in for the well, rigged up the pumping equipment, erected the derrick, etc., then you remember how long it took to get everything in place and installed correctly. Now you have to reverse the process, break everything down, and pull everything out. That requires a crane and a few other pieces of extraction equipment.
Dirt, Lots of Dirt
The problem with most wells, regardless of the type (e.g., oil, gas, water, etc.), is that they leave giant holes in the ground. Consider the dangers of a simple water well, and then consider how much deeper an oil or gas well goes. You definitely do not want anyone, man, woman, or child, falling down an old well of yours. Fill it with dirt, lots of dirt, and leave a mound of dirt over the top to accommodate for shifting and sinking of earth over time. It also helps to use a well sealing cap first, and then mound dirt over the top of that. Whichever option you choose, be sure to construct a fence perimeter and/or some appropriate signage around the well to warn others to stay away.