Seal section for a downhole pumping unit

A seal section for a downhole well pumping apparatus of the type having an oil filled motor drivingly connected to a pump via a shaft passing through the seal section, comprising:

• a plurality of vertically spaced seal heads between the motor and pump, each seal head having a bore formed therethrough for passage of the shaft therethrough and each seal head having bearing means rotationally supporting the shaft;
• a plurality of tubular casing members interconnecting the seal heads and forming therewith a plurality of vertically stacked, annular compartments centered on the shaft;
• and
• a plurality of balance chamber forming assemblies, each assembly disposed in one of the compartments and comprising:
• a tubular balance chamber outer wall member, connected solely to the uppermost of the two seal heads delimiting the compartment wherein the balance chamber outer wall member is disposed, each balance chamber outer wall member extending downwardly from such uppermost seal head in a concentric relation to the casing member thereabout to terminate in a free end positioned in a non-engaging relation with the lowermost seal head delimiting the compartment wherein the balance chamber outer wall member is disposed;
• and
• a tubular balance chamber inner wall member, connected solely to the lowermost of the two seal heads delimiting the compartment wherein the balance chamber inner wall member is disposed, each balance chamber inner wall member extending upwardly from such lowermost seal head inside the balance chamber outer wall member disposed therewith in such compartment and concentric with such balance chamber outer wall member to terminate in a free end positioned in non-engaging relation with the upper seal head delimiting the compartment wherein the balance chamber inner wall member is disposed;
• wherein the uppermost of the seal heads is characterized as having means fluidly communicating portions of the bore therethrough near the upper end thereof with the exterior of the balance chamber outer wall member in the annular compartment therebelow;
• wherein the lowermost of the seal heads is characterized as having means fluidly communicating the interior of the motor with the interior of the balance chamber inner wall member in the annular compartment thereabove;
• wherein remaining seal heads are characterized as having means fluidly communicating the interior of the balance chamber inner wall member in the compartment thereabove with the exterior of the balance chamber outer wall member in the compartment therebelow;
• wherein each seal head above the lowermost thereof is characterized as having seal means for providing a fluid seal between the shaft and the bore therethrough;
• and wherein the shaft is supported in the passage thereof through the seal section solely by the bearing means disposed in the seal heads.