Downhole pumps with outside pressure balancing and sand separation and isolation

The present disclosure relates to a downhole pump designed to include a sand separation unit. In one implementation, the downhole pump comprises a barrel having a first valve for controlling fluid flow into the barrel. The first valve includes an interior cavity with a first surface. The downhole pump further includes a plunger housed within the interior cavity of the barrel. The plunger comprises a wiper-plunger having a first circumference to which one or more resilient seals are coupled. The one or more resilient seals seal a first boundary between the first circumference of the wiper- plunger and a first portion of the first surface associated with the barrel. The plunger further comprises a sand separation unit coupled to the wiper-plunger at a first side. The sand separation unit forms a balancing chamber that minimizes a pressure differential across the one or more resilient seals. The sand separation unit uses centrifugal force to separate particulate matter from fluid during a first motion of the wiper-plunger relative to the first portion of the first surface associated with the barrel. The plunger further comprises a plunger-assembly coupled to the sand separation unit at a second side. The plunger-assembly has a second valve that controls fluid flow into the plunger-assembly via a third side from the interior cavity of the barrel. Additionally, the plunger includes a second boundary between a second circumference of the plunger-assembly and a second portion of the first surface associated with the barrel. The second boundary is fillable by slippage fluid within the barrel to create a fluid seal at the second boundary.