This article describes the procedure for conventional external gravel packing.
1.With the liner set and the gravel pack tool in the circulating position establish circulation at 0.5-5 bbls/min.
2.Commence adding gravel at ± 1/2sack per min (i.e. ± 1/8sack/bbl).
3.Having reached 80-85% of theoretical fill (or earlier if pressures indicate) reduce the gravel concentration to 1/8-1/4sack/min. When getting close to screen out, it may be necessary to add 1-2 sacks and displace these completely before adding the next batch of gravel. Care should be taken that the string is not full of gravel at screen out.
4.Continue packing to screen out at reduced rate with 500 psi above initial pressure at 0.5 bpm. Do not exceed the maximum surface circulation pressure specified in the programme.
5.If there is no screen out or pressure build up after 100% of theoretical annular fill, this could be due to washing out of the underreamed section or slumping of the pack due to unconsolidated formation or tool failure resulting in gravel falling on top of running tool or BOL. In this case, check tool is still free. If there is no indication of tool failure, continue packing at reduced rate to screen out or a pressure build up followed by losses.
6.If no screen out occurs after 150% theoretical annular fill, double check system for leaks, packer failure, fill inside liner, etc. Consideration can be given to run gravel pack log to determine quality of pack (Base to advise).
7.After initial screen out reverse out excess gravel in DP. Wait for one hour and recheck screen out at same pressure, in circulating position. Repack if necessary.
8.If screen out occurs before 90% theoretical annular fill, consideration should be given to running a gravel pack log, as it may be necessary to check for bridging to determine whether the bridge should be jetted or the liner pulled (Consult base).