1. SAND PRODUCTION ON WATER INJECTORS: JUST HOW BAD CAN IT GET ? SAND PRODUCTION ON WATER INJECTORS: JUST HOW BAD CAN IT GET ? F.J. Santarelli (ORMIS), E.Skomedal, P. Markestad, H. Nasvig and H.I. Berge (Statoil) Paper SPE 47329

2. STRUCTURE INTRODUCTION HISTORY OF SUBSEA WELLS ROCK MECHANICS CONDITIONS CROSS FLOW PARTICLE SETTLING DURING SHUT IN PERIODS SUDDEN WELL LOSSES FIELD EVIDENCE OF WATER HAMMER AND SAND LIQUEFACTION OPERATIONAL CONSEQUENCES CONCLUSION INTRODUCTION HISTORY OF SUBSEA WELLS ROCK MECHANICS CONDITIONS CROSS FLOW PARTICLE SETTLING DURING SHUT IN PERIODS SUDDEN WELL LOSSES FIELD EVIDENCE OF WATER HAMMER AND SAND LIQUEFACTION OPERATIONAL CONSEQUENCES CONCLUSION

3. Paper SPE 47329 INTRODUCTION SAND PRODUCTION RISK IS HIGHEST ON PRODUCERS Flow Gradient Bringing Sand to Surface SAND PRODUCTION ON PRODUCERS IS WELL STUDIED (and understood) SAND PRODUCTION RISK IS HIGHEST ON PRODUCERS Flow Gradient Bringing Sand to Surface SAND PRODUCTION ON PRODUCERS IS WELL STUDIED (and understood) ALMOST NOTHING PUBLISHED ABOUT INJECTORS FIELD CASE OF SAND PRODUCTION ON INJECTORS WITH CATASTROPHIC PRACTICAL CONSEQUENCES FIELD CASE OF SAND PRODUCTION ON INJECTORS WITH CATASTROPHIC PRACTICAL CONSEQUENCES

4. Paper SPE 47329 WELL HISTORY OCT. 95 COMPLETION FIRST BACK PRODUCTION JAN. 96 SECOND BACK PRODUCTION MAY 96SEP. 96 WORK OVER INJECTIVITY (?) Important Sand Fills Often Above Top Perforation Good Injectivity Recovery No Effect or Worsening

5. Paper SPE 47329 WELL HISTORY Time (min) Logarithm of Pressure Ratio 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 0102030405060708090100 1st Shut In 2nd Shut In Near Wellbore Regime Near By Fault Regime 5 SUDDEN WELL LOSSES

6. Paper SPE 47329 ROCK MECHANICS CONDITIONS 10 bar < UCS < 80 bar FAILURE DURING SHUT INS ROCK AROUND CASING IS FAILED AND CAN PRODUCE SAND 10 bar < UCS < 80 bar FAILURE DURING SHUT INS ROCK AROUND CASING IS FAILED AND CAN PRODUCE SAND

7. Paper SPE 47329 CROSS FLOW CROSS FLOW FROM LOW k TO HIGH k

8. Paper SPE 47329 PARTICLE SETTLING 6507/7-B-3H Depth (m MD-RKB) % of Particles in Suspension 0,00 10,00 20,00 30,00 40,00 50,00 60,00 70,00 80,00 3240325032603270328032903300 0.5 hours 6 hours PARTICLES MAY REMAIN IN SUSPENSION

9. Paper SPE 47329 PARTICLE SETTLING Low Permeability High Permeability Rat Hole Perforated Interval Formation Sand CROSS FLOW Low Permeability High Permeability Rat Hole Perforated Interval Formation Sand RE-START INJECTION Coarser Grains Settled in Rat Hole Smaller Grains Reinjected

10. Paper SPE 47329 PARTICLE SETTLING

11. SUDDEN WELL LOSSES Pipe Open Valve Fluid Layer BEFORE CLOSURE Pipe Closed Valve Fluid Layer AFTER CLOSURE Depressurised Layers Overpressurised Layers v vv v = 0

12. Paper SPE 47329 SUDDEN WELL LOSSES Time Closure 2th  ph At the Valve TimeClosure 2th pp At the Rock Face th  pf

13. Paper SPE 47329 WATER HAMMER AND SAND LIQUEFACTION

14. Paper SPE 47329 WATER HAMMER AND SAND LIQUEFACTION

15. Paper SPE 47329 WATER HAMMER AND SAND LIQUEFACTION Top Sand Fill Liquefied Zone DURING INJECTION Top Sand Fill “Emptied” Liquefied Zone Top Perforation Top Perforation Sand Movement DURING PRODUCTION WELL CLEN UP

16. Paper SPE 47329 OPERATIONAL CONSEQUENCES TWO MECHANISMS LED TO DRAMATIC INJECTIVITY LOSSES THE FIELD WENT OFF PLATEAU AS A CONSEQUENCE THE SHUT DOWN PROCEDURES HAVE BEEN CHANGED THE REOPENING OF THE WELLS IS ALWAYS DELAYED THE SHUT DOWN PROCEDURES HAVE BEEN CHANGED THE REOPENING OF THE WELLS IS ALWAYS DELAYED INJECTIVITY LOSSES HAVE DISAPPEARED THE FIELD IS BACK TO PLATEAU INJECTIVITY LOSSES HAVE DISAPPEARED THE FIELD IS BACK TO PLATEAU

17. Paper SPE 47329 CONCLUSIONS SAND PRODUCTION ON INJECTORS IS OFTEN IGNORED YET FIELD CASES SHOW IT CAN HAVE DRAMATIC CONSEQUENCES (FIELD OFF PLATEAU) TWO MECHANISMS OF INJECTIVITY LOSSES HAVE BEEN IDENTIFIED: Sand Produced by Cross Flow is Reinjected and Plugs Perforation Tunnels Pressure Wave Liquefy Sand in the Perforated Interval PROCESS MODIFICATION ARE REQUIRED SOMETIMES SAND CONTROL IS COMPULSARY SAND PRODUCTION ON INJECTORS IS OFTEN IGNORED YET FIELD CASES SHOW IT CAN HAVE DRAMATIC CONSEQUENCES (FIELD OFF PLATEAU) TWO MECHANISMS OF INJECTIVITY LOSSES HAVE BEEN IDENTIFIED: Sand Produced by Cross Flow is Reinjected and Plugs Perforation Tunnels Pressure Wave Liquefy Sand in the Perforated Interval PROCESS MODIFICATION ARE REQUIRED SOMETIMES SAND CONTROL IS COMPULSARY