the primary ball seat causes the primary ball seat to slide sufficiently so that an opening therein becomes substantially aligned with the annular bypass port 386 so as not to obstruct it thus fluid may freely flow from a first annular space 347 proximal of the gravel packer through the internal cross over tool channels and into the interior channel at a location distal of the first plugging device thus annular pressure is maintained on the formation to help maintain its integrity prior to gravel pack operations once set the gravel packer must be tested step 210 and to test the packer the annular bypass port must once again be closed to isolate the annular fluid above the packer as shown in fig5 the proximal end 336 of the service tool assembly is uncoupled from the gravel packer 320 and the service tool assembly is partially retracted from within the gravel packing assembly this movement of the service tool assembly relative to the gravel packing assembly opens the temporary closing sleeve 368 thereby allowing fluid flow between the interior channel 338 and the exterior of the gravel packing assembly further this movement also causes a temporary interference collar 390 of the gravel packer assembly to engage a service tool isolation valve.