Adjustable screen size using interchangeable shrouds

A method for filtering a fluid in a wellbore with a well screen assembly, the method comprising:

• selecting a configuration of interchangeable solid and perforated outer shrouds of the well screen assembly based on which filtration layers to block from or expose to fluid communication outside of the outer shrouds to filter a specified size of particulates from the fluid, wherein the well screen assembly comprises a base pipe defining an interior bore and comprising fluid passageways configured to provide fluid communication between the wellbore and the interior bore for the fluid, the filtration layers being disposed around the base pipe at different axial locations along the base pipe and each filtration layer configured to filter particulates from the fluid as the fluid flows through the filtration layers and into the interior bore;
• lowering the well screen assembly to a depth in the wellbore;
• flowing the fluid through each perforated outer shroud and into the respective filtration layer to filter the particulate from the fluid;
• and
• flowing filtered fluid through the fluid passageways and into the interior bore.

A system comprising:

• a tubing string within a wellbore;
• a base pipe connected in the tubing string, the base pipe defining an interior bore and comprising fluid passageways configured to provide fluid communication between the wellbore and the interior bore;
• filtration layers disposed around the base pipe at different axial locations along the base pipe, each filtration layer configured to filter particulates from a fluid of the wellbore as the fluid flows through the filtration layers and into the interior bore;
• and
• outer shrouds each disposed about a filtration layer and removably coupled to the base pipe, each outer shroud comprising either a solid outer shroud blocking fluid communication from outside the outer shroud to the filtration layer or a perforated outer shroud allowing fluid communication from outside the outer shroud to the filtration layer,
• wherein, for each filtration layer, the outer shroud is selectively interchangeable with either a solid outer shroud or a perforated outer shroud to block or allow fluid communication with the respective filtration layer, and
• wherein a configuration of solid and/or perforated outer shrouds is based on selected filtration layers for use in filtering the fluid from the wellbore.