Design Optimization of Slotted Liner Completions in Cased and Perforated Wells: A Numerical Skin Model

Abstract Several parameters affect the skin factor of the cased and perforated (C&P) wells completed with slotted liners. Existing skin factor models for slotted liners account for such factors as the flow convergence, pressure drop and partial production but neglect phenomena such as partial plugging of the screen or near-wellbore permeability alterations during the production. This paper discusses these factors and incorporates them into a skin model using a finite volume simulation. The finite volume analysis evaluates the skin factor as a result of pressure drop in the gap between the casing wall and the slotted liner. This skin model accounts for: 1) the perforation density and phasing, 2) slotted liner specifications, and 3) different amount of sand accumulation in the annular space between the casing and the sand screen. A semi-analytical pressure drop model is also linked to the numerical model to incorporate the skin factor due to flow convergence behind the perforations. The results of finite volume analysis reveal that a low perforation density would behave close to the open-hole completion for sand-free casing-liner annular space. Conversely, pressure drops were found to be significant for a partially or totally filled space. Additionally, it was found that the optimum completion design occurs if the slotted liner joints are in line with the casing joints. Besides, a partially perforated casing or a partially open sand screen increases the distance fluids have to travel in the annular space and intensifies the skin factor. This paper provides skin models derived for vertical and perforated wells completed with slotted liner sand screens using the finite volume simulations. Each part of the model has been verified against existing numerical models in the literature. The model improves the understanding of flow performance of the sand screens and skin factor, which in turn leads to a better design of sand control completions.