Advanced Lift Systems : Pod Systems

Advanced Lift Systems : Pod Systems

Applications :

• Diverts fluids from below an isolation packer into the ESP, while  isolating  casing  from production fluids (eg for wells with worn casing or corrosive fluids) 
• Suspend long tailpipes, or heavy assemblies below an ESP 
• Dump flood applications, where fluid is produced from one zone and injected into another 
• Can be used to deploy a second ESP for back up purposes 
• Can be used to deploy a second ESP to ‘boost available downhole’ horsepower  and provide increased lift capability 
• Can be used in conjunction with a bypass system to produce multiple zone wells with multiple ESPs

Features :

• Fully encapsulates the ESP in a pressure tight shroud (Pod) 
• Available to suit a range of casing sizes, and ESP series 
• Available in a choice of metallurgies to suit well environment 
• Available to suit Single or Dual Pod configurations 

Description and Operation :

A Pod system is used to encapsulate an electrical submersible pump (ESP) within a sealed shroud. Fluids are diverted  into the annulus created by the Pod casing. The pump produces the fluids through the production tubing. 

The Pod system comprises of a Pod Hanger Assembly, Pod Sleeve assembly, Casing Joints, and a Bottom Crossover Assembly. Depending on the application Pod Clamps and a Nipple Sub assembly may also be included. Dedicated handling equipment is provided to aid assembly of the Pod system at the well site.   

The Pod system sub assemblies and accessories are described in more detail on individual datasheets. 

The Pod system can be used, or combined with other equipment to achieve a number of operational benefits. More information on these can be found overleaf.  

Pod System Exploded Diagram :

Casing Isolation Application :

The Pod system can be used in applications with corroded or worn casing, or where corrosive production fluids are anticipated. The ESP is encapsulated in the Pod. Tailpipe below the Pod includes a seal assembly which locates into a seal bore packer.  In this configuration the production fluid remains isolated from the casing. 

During operation the fluids from the reservoir are directed from below the packer, through the tailpipe and into the Pod. The fluid  is then lifted to surface by the ESP, through the production tubing. 

This configuration can also be used to suspend long tailpipe or other heavy completion assemblies below the ESP. As the ESP is suspended within the Pod assembly, all the tailpipe tensile load is transferred to the production tubing string by the Pod assembly.  

Refer to the table at the end of this post for applicable Pod Sizes.  

DuaLife Back-Up ESP :

The Pod system can be used as a means to deploy a second, or back up ESP within the well bore. The back up ESP can be suspended below the Pod assembly. Auto Flow Subs are included above each ESP to allow the non-operating ESP to be bypassed.   

When the lower ESP is operating, the fluid is produced by the ESP into the Pod. The fluid passes the upper ESP and enters the tubing string above the ESP through the open Auto Flow Sub. 

When the upper ESP is operating the fluid enters the tailpipe tubing string above the  lower ESP through the lower Auto Flow Sub. The fluid then flows into the Pod and is produced by the upper ESP. 

The Auto Flow Sub operation is detailed below. 

Pod clamps are fitted to the outside of the upper Pod to secure the lower ESP cable as it passes the outside of the assembly.  

DuaLife Back-Up ESP with Casing Isolation :

Where well control or casing corrosion is a concern, the lower ESP can  also be deployed within a Pod.  In this configuration the production fluids remain isolated from the casing.

UltraHi Boost System :

The Pod system can be used to enable ESPs to be operated in series for applications  with high lift (head) requirements. In this configuration the lower ESP discharges into the upper Pod, where it is ‘boosted’ by the upper ESP, and produced to surface through the production tubing.  

In high lift wells motor or shaft horse power ratings may become a limitation. In this configuration the total horse power requirement is shared between multiple ESPs. This  can enable high horse power systems to be deployed within casing constraints. 

The system can be designed so that each ESP can produce to the surface independently.   This provides additional built-in redundancy in the event that a pump should prematurely fail.

Multiple Zone System :

The Pod system can be combined with other Artificial Lift completion equipment to produce from multiple zones.

The lower ESP is housed  in a Pod. Below the Pod, a tailpipe string and seal assembly locates in a seal bore packer which separates the perforated zones. The fluid from the lower zone flows into the Pod and is produced by the lower ESP.

The upper ESP includes a bypass system.  The bypass tubing alongside the upper ESP allows the flow from the lower ESP to pass the upper ESP, where it reaches the Y-Tool.  

The fluid from the upper zone is produced by the upper ESP. The fluids from both zones are co-mingled at the Y-Tool and produced to surface through the production tubing.

Alternatively a concentric tubing string can be configured to enable the fluids to be produced separately (non-commingled) to surface through the two tubing strings.

Zones can be produced either independently, or simultaneously, while running upper, lower,

or both ESPs.

Auto Flow Sub Operation :

In  some ESP wells there will be  periods  where fluid has to flow through a non-operating ESP, for example in wells capable of natural flow, or wells equipped with a back up ESP. When fluid flows through a non-operational pump, the pump stages create a flow restriction, and unnecessary pump wear occurs.

The Auto Flow Sub allows fluids to flow past a non operational ESP and enter the tubing string unrestricted by the pump. When the ESP is not operating the Auto Flow Sub automatically by-passes the ESP by creating an open port between the annulus and the production tubing above the ESP.  When the ESP is started, the port is automatically closed, allowing the ESP to produce normally to surface.

The Auto Flow Sub can be used in any ESP application where the well can naturally flow, or where gas lift is included as a secondary artificial lift method.

The Auto Flow Sub can also be used in both Single and Dual Pod completions, to bypass the non operational ESP(s).  Refer to the diagram below for illustration of Auto Flow Sub operation in the dual Pod system:

Pod Casing and ESP Sizes :

The correct Pod casing size for a given application is based upon a number of variables :

• Casing size and weight. 
• ESP series. 
• External cables / control lines (dimensions). 
• Pod system configuration (e.g. single or dual ESP). 
• ESP motor cooling requirements. 
• Type of Pod system casing (coupled or flush joint). 

The table below shows typical Pod casing sizes, although each application should be sized individually: