passageway 56 and the firing head 36 for purposes of communicating pressure to the firing head 36 to cause the firing head 36 to fire for example as depicted in fig2 the bottom end of the service tool 42 is received into the extension sleeve 41 of the packer and sandscreen extension assembly 39 and is aligned such that radial ports 66 of the sleeve 61 are aligned to communicate fluid between the passageway 56 and the isolated interval below the packer 38 the sleeve 61 is generally concentric with the longitudinal axis 51 of the bha 30 referring to fig3 in general a perforating and gravel packing technique 100 operation may be performed in the well 10 using the string 20 in accordance with some embodiments of the invention referring to fig3 in conjunction with fig1 and 2 the technique 100 includes running the bha 30 to the appropriate depth and locating the sump packer 24 pursuant to block 104 after the sump packer 24 is located the fluid in the borehole may be changed to a desired weight pursuant to block 108 more specifically the targeted fluid weight may depend on the desired balance at the time of perforating for example in certain situations the well may be underbalanced to create a flow from the resulting perforation tunnels into the wellbore for purposes of assisting in cleaning debris from the perforation tunnels the fluid in the well at the time of perforating may be placed prior to or at the time of the firing of the perforating charges 80 depending on the particular embodiment of the invention still referring to fig3 when the fluid condition is correct the bha 30 is stabbed block 112 into the sump packer 24 to establish a.