Integrity testing of a polyvinyl chloride slotted liner for horizontal coalbed-methane wells

Steel slotted liners are often used in horizontal coalbed-methane (CBM) well completions. However, the disadvantages associated with these liners, such as high operation costs, corrosion susceptibility, and safety considerations in subsequent mining processes, can limit their performance. One possible alternative is a plastic slotted liner. A major challenge for designing a plastic slotted liner is providing sufficient structural integrity without creating a significant restriction for gas that flows into a wellbore. In this paper, we present an optimization design for polyvinyl chloride (PVC) slotted liners. Our design couples the influence of the mechanical integrity of the liner and the inflow performance. The optimization parameters are the slot geometrical parameters. The boundary conditions are identified by the failure criteria and the influence of various slot-parameter adjustments through laboratory compression experiments. Two models-a collapse-bearing- capacity model and a skin-factor model (Furui et al. 2005)- are used to optimize the design of the PVC slotted liners. A genetic algorithm is used to maximize the collapse-bearing capacity and minimize the skin factor. Finally, a selection guide for the optimal combination of slot parameters is provided. The key findings of this work are beneficial for determining the design criteria of plastic slotted liners in horizontal CBM wells. In addition, the proposed "cross-disciplinary" evaluation method is expected to provide a valuable optimization approach for slotted-liner completions. Copyright © 2017 Society of Petroleum Engineers.