Liners in horizontal thermal wells do occasionally have production inflow problems and fail. Published literature exists on the risks and design issues related to the effects of thermal expansion on slotted liners in horizontal wells. This paper investigates two areas of liner behaviour that seem to have been somewhat overlooked. It examines: (1) the potential effects of thermal expansion or contraction on screened liners and (2) the effects of thermal contraction on slotted and screened liners.

Upon injection of steam, horizontal liners will expand or contract and be subject to compressive or tensile axial stresses. Whether the stress is compressive or tensile depends on when the formation closes in on the liner. If it closes in before the well is steamed, the stress will be compressive; if it closes in after steaming the stress will be tensile.

This paper examines the effects of shear force from the formation on the screens of liners both in expansion and contraction. It would appear that to some extent the shear or tearing forces on screens are self-limiting making them more resistant to tearing than might be expected.

The paper also examines effects on liners of tensile forces caused by contraction and cooling. Tensile forces on liners can approach and exceed yield under common operating conditions. The liners are then susceptible to slot closure and collapse.

Limits on operating conditions are presented to reduce the risk of such failures. Suggestions for further R&D on the subject are also made.

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