<![CDATA[Swabbing is a liquid unloading method used in the oil and gas industry to reduce hydrostatic pressure caused by fluid accumulation in the wellbore. In wells with dual-size tubing completions (4.5-inch and 3.5-inch), tubing diameter transitions can reduce Swab Cup sealing performance, causing fluid bypass and lowering lifting efficiency. This study develops a modified Swab Cup Carrier and swab mandrel to support continuous fluid lifting in dual-size tubing completions. An engineering design research approach was applied, including field problem identification, conceptual design, Computer-Aided Design (CAD), Finite Element Analysis (FEA), prototype development, tubing simulation, and functional evaluation. The proposed design incorporates a cam-guided release-and-carry mechanism that enables the Swab Cup Carrier to release at the tubing X-over during Run In Hole and reconnect during Pull Out of Hole. FEA of AISI 4130 alloy steel showed a maximum von Mises stress of 278.6 MPa, below the material yield strength of 460 MPa, indicating adequate structural safety. Prototype testing using a PVC tubing simulation verified the proposed mechanism. The design has the potential to minimise fluid bypass, maintain lifting continuity, and improve swabbing effectiveness in dual-size tubing completions. Further laboratory and field validation is required to confirm its operational performance.]]>
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