Retrievable Downhole Pump Tapered Shoulder Retrieval
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Solution Overview
Problem
Existing downhole pumping systems require removal of the production tubing string to retrieve the downhole pump for maintenance or flushing, which is impractical and costly, especially when the pump length exceeds 30 feet, as it necessitates expensive single-length sucker rods and specialized rigs.
Innovation Solution
A retrievable downhole pumping system with a tapered internal shoulder on the lifting member allows the rotor to be pulled from the stator without unseating the pump, using a drive coupling and rod couplings to engage and disengage the pump from the landing nipple, enabling reliable flushing and retrieval without extending the pumping system length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an extension tube is added to allow rotor pullout for flushing operations, then the pump can be flushed without retrieval, but the system length increases and may require expensive single-length sucker rods exceeding 30 feet
Solution Approach 1:
The pumping system is divided into separable components: the pump assembly (stator and rotor) and the extension tube. The extension tube can be independently added or removed based on operational needs, allowing flushing operations without permanently increasing system length. This segmentation enables the system to adapt between compact configuration for normal operation and extended configuration for flushing operations.
Solution Approach 2:
The system transitions from a static configuration to a dynamic one where the extension tube can be selectively positioned. During flushing operations, the extension tube is inserted to provide the necessary length for rotor pullout. During normal pumping operations, the extension tube is removed or retracted, maintaining a compact 30-foot sucker rod length. This dynamic adaptability resolves the contradiction between flushing capability and system length.
2Ease of operation
If a single-length sucker rod of 50 feet or more is used to enable flush by operations, then the rotor can be pulled out for flushing, but the cost increases and specialized workover rigs are required
Solution Approach 1:
Rather than using a single expensive 50-foot sucker rod, the system segments the extension function into a separate, inexpensive extension tube that can be added to standard 30-foot sucker rods. This eliminates the need for costly custom-made long sucker rods and specialized workover rigs, as the extension tube is a simple, low-cost component that can be handled with conventional equipment.
Solution Approach 2:
The extension tube is designed as a simple, inexpensive component that can be easily manufactured and replaced. Instead of investing in expensive single-length long sucker rods, the system uses multiple affordable extension tubes that can be selectively deployed. This approach dramatically reduces the cost of enabling flush by operations while maintaining full functionality.
3Ease of operation
If the drive coupling outer diameter is larger than the lifting nut internal diameter to enable pump retrieval, then the pump can be retrieved without tubing removal, but the rod coupling may inadvertently engage the lifting nut during flushing operations and unseat the pump
Solution Approach 1:
The tapered internal shoulder acts as an intermediary mechanism between the rod coupling and the lifting nut. During flushing operations, the tapered shoulder guides the rod coupling to engage at an offset position that provides sufficient leverage to pull the rotor out of the stator without engaging the lifting nut. This intermediary feature ensures that the rod coupling interacts with the system in a controlled manner that prevents inadvertent pump unseating while still enabling rotor extraction.
Solution Approach 2:
The lifting nut features an asymmetric tapered internal shoulder rather than a symmetric cylindrical bore. This asymmetry creates a specific engagement geometry where the rod coupling contacts the tapered surface at an offset position during flushing operations. The asymmetric design ensures that the engagement point provides the necessary mechanical advantage for rotor pullout while the geometry prevents the coupling from reaching the lifting nut seating surface, thereby maintaining pump stability.
Data Source
AI summary
A pumping system 10 is provided for pumping fluid from a downhole well to the surface through a production tubing string well. A rotatable drive rod 18 extends from the surface to power the downhole pump, and includes a plurality of rod couplings. The downhole pump includes a pump stator 22 and a rotor 24 rotatable within the pump stator. A lifting member 36 provided at the upper end of the stator is engaged by a drive coupling 34 to retrieve the pump from the well. The lifting member has an internal shoulder 44 tapered radially inwardly and upwardly, such that a rod coupling engages the internal shoulder and passes through the lifting member as the rotor is pulled upward.