Although there have been plenty of advancements over the years, the basics of the pump-jack extraction process remain more or less the same as they have for so long. As will be clear to anyone who sees such a well in action, the up and down motion of the pump head itself is what allows for oil to be pulled up from the ground. Instead of acting directly on the oil from so far above, however, what an above-ground pump-jack well does is transfer power to a pump a long ways below.
Transmitting the bobbing head's power over such a distance requires a mechanical linkage that is up the task and all the associated stresses. In just about every case, this is provided by a special piece of equipment known as a "sucker rod." Typically made of strong galvanized steel fence posts and threaded at each end, an individual length of sucker rod is designed to be fitted to as many others as might be needed to cover the distance between the pump-jack head and the subterranean pump itself.
In most cases, equipment of this kind is designed according to certain well-established standards. Because sucker rods are available in various diameters that together accommodate all these common variations, suitable ones tend to be relatively easy to find, regardless of the details of a particular project. Once a well has been drilled and judged ready for extraction, rods will therefore normally be assembled and used to link a pump-jack to the equipment positioned below the ground.
When deployed and maintained properly, this generally turns out to be an efficient, cost-effective way of extracting oil. This is one reason for why the arrangement has remained generally unchanging for so long, even while plenty of less noticeable advancements have arrived. Offering a reliable form of service with a low barrier to entry and well-understood requirements, this style of extraction often makes excellent sense.