Are You Overlooking a Key Design Element in Your ESP System?
Due to the costs associated with implementing an Electric Submersible Pump (ESP) system most operators are very focused on maximizing reliability. Historically, however, the Seal component has not mandated the same level of technical investigation as other downhole components.
ESP Seal design is still perceived by many as an empirical process. It is not clear how key design parameters, such as bag expansion/contraction volumes, relief valve opening pressure, and flow passage areas are established. It is also assumed that the ESP Seal will operate primarily under steady-state conditions, and that it will be able to withstand the transient pressure and temperature conditions that occur when operating conditions change (i.e. during startup and shutdown).
Testing of an ESP Seal Chamber is usually limited to Factory Acceptance Tests (FATs) done by equipment manufacturers according to the API RP 11S7. These tests help ensure that the ESP Seal Chamber has been properly manufactured and assembled. They are usually conducted at ambient temperature and very low pressures (15 psig) and include basic functionality tests for the shaft seals, relief valves, bags (bladders), and the thrust bearing.
It is clear that ESP Seal Chamber performance and reliability, especially under transient conditions, is a concern and that further validation testing should be conducted under full lifecycle operating conditions.
Simulating Real Down-hole Conditions to Maximize ESP Seal Design
Working with a major operator C-FER designed and constructed a custom test apparatus to simulate the down-hole conditions that an ESP Seal Chamber would experience throughout its life-cycle. These conditions include transient pressure and temperature conditions that occur during startups and shutdowns.
With this new ESP Seal Chamber Testing Apparatus, C-FER conducted a test campaign on various commercially available ESP Seals.