Aspects of this topic are discussed in the following places at Britannica.
...beam” (an arm that rises and falls like a seesaw) on the surface. A string of solid metal “sucker rods” connects the walking beam to the piston of the pump. Another method, called gas lift, uses gas bubbles to lower the density of the oil, allowing the reservoir pressure to push it to the surface. Usually, the gas is injected down the annulus between the casing and production...
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