the expandable sand screen 20 and the formation wall 48 the encapsulation 10 is designed to serve as a housing for control lines or instrumentation lines 62 or control instrumentation not shown for purposes of this application such lines 62 include any type of data acquisition lines communication lines fiber optics cables sensors and downhole u201c smart well u201d features the encapsulation 10 may optionally also house metal tubulars 60 for holding such control or instrumentation lines 62 the encapsulation 10 is specially profiled to closely fit between the sand screen 20 and the surrounding formation wall 48 after the sand screen 20 has been expanded in this way no vertical channel is left within the annular region 28 after the sand screen 20 is been expanded to accomplish this an arcuate configuration is employed for the encapsulation 20 whereby at least one of the walls 12 and 14 is arcuate in shape in the preferred embodiment shown in fig2 both walls 12 and 14 are arcuate such that a crescent shape profile is defined thus the encapsulation 10 shown in fig2 comprises a first arcuate wall 12 and a second arcuate wall 14 sharing a first end 15 u2032 and a second end 15 u2033 however it is only necessary that the outside wall 12 be arcuate in design the encapsulation 10 is normally fabricated from a thermoplastic material which is durable enough to withstand abrasions while being run into the wellbore 40 at the same time the encapsulation 10 material must be sufficiently malleable to allow the encapsulation to generally deform to the contour of the wellbore 48 this prevents annular flow.