A pump consisting of a piston (Plunger) that moves up and down in a cylinder (barrel). The pump is equipped with standing valve (suction) and travel valve (discharge). On the upstroke the standing valve opens and fluid is drawn into the pump. On the down stroke, the standing valve closes and the travel valve opens, and fluid is forced out of the pump.
At the bottom of the borehole is the "down-hole pump". This pump consists of two ball valves: a stationary valve attached the barrel called the "standing valve" and a travel valve connected to the bottom of the plunger. The plunger is connected to the bottom of the sucker rods that travels up and down as the pump Jack reciprocates, Reservoir fluid seeps from the formation into the bottom of the borehole through perforations that have been made through the casing and cement (casing is a larger metal pipe that runs the length of the well, which has cement placed between it and the earth. |
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The tubing, pump and sucker rods are all inside the casing). When the rods are traveling up, the traveling valve is closed and the standing valve is open (due to the drop in pressure in the pump barrel). Consequently, the pump barrel fills with the fluid from the formation as the traveling piston lifts the previous contents of the barrel upwards.
When the rods begin pushing down, the traveling valve opens and the standing valve closes (due to an increase in pressure in the pump barrel). The fluid in the barrel (which was sucked in during the upstroke) flows up through the traveling valve. The piston then reaches the end of its stroke and begins its path upwards again, repeating the process.
Often, gas is produced through the same perforations as the oil. This can be problematic if gas enters the pump, this can result in "gas locking", where insufficient pressure builds up in the pump barrel to open the valves (due to compression of the gas) and little or nothing is pumped. To avoid this, the inlet for the pump is placed below the perforations. When the gas enters the well bore through the perforations, it bubbles up the annulus (the space between the casing and the tubing) and does not have space to make it into the pump. Once at the surface, the gas is collected through a tube connected to the annulus. |
