RECIPROCATING ROD PUMP FOR SANDY FLUIDS

A downhole pump has a barrel and a plunger movably disposed therein. The gap between the barrel and plunger has first and second seals. The barrel and plunger each have a one-way valve restricting fluid passage out of it. A filter or screen is disposed on the plunger between the first and second seals. In a downstroke, fluid and particulate in the barrel transfers into the plunger. In an upstroke, fluid and particulate in the plunger lifts uphole. At the same time, a volume in the barrel fills with fluid and particulate. During either stroke, the first seal prevents particulate uphole of the plunger from passing into the gap. The filter or screen, however, prevents at least some particulate (i.e., most or larger particulate) inside the plunger from passing out of the plunger with fluid flowing into the gap between the first and second seals.