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Formation damage from perforating and cementing

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When cement is bullheaded into the annulus to displace mud, the differential pressure between the cement and the formation fluid can lead to a significant loss of cement filtrate into the formation. If, however, large volumes of cement filtrate invade the rock, the possibility of formation damage exists.

Cement filtrates

The major constituents in the aqueous phase in contact with hydrating cement are:

  • Calcium silicates
  • Calcium aluminates
  • Calcium sulfates
  • Calcium carbonates or bicarbonates
  • Alkali sulfates

Depending on the specific composition of the cement and its pH, the filtrate may be supersaturated with calcium carbonate and calcium sulfate. As the cement filtrate invades the formation and reacts with the formation minerals, its pH is reduced from > 12 to a pH buffered by the formation minerals. This rapid change in pH can result in the formation of inorganic precipitates such calcium carbonate and calcium sulfate.

Damage mechanisms

Evidence of formation damage induced by cement filtrates has been clearly demonstrated in experimental studies presented in Cunningham and Smith[1]and Jones, et al.[2]. Cunningham and Smith[1] investigated the influence of cement filtrates on formation permeability and concluded that there was little evidence of fines migration or clay swelling induced by the cement filtrate. They observed severe permeability reductions of 60% to 90% in cores invaded by cement filtrate. Yang and Sharma[3] investigated the impact of cement additives such as lignin derivatives, cellulose derivatives, organic acids, and synthetic polymers on the extent of permeability reduction in cores exposed to cement filtrate. In that study, cement filtrate was injected immediately after filtration into a sandstone core. Reductions in permeability of 40% to 80% were observed up to 6 in. into the core. Most of the damage observed was attributed to the precipitation of insoluble material such as calcium carbonate and calcium sulfate in the core. The quantity of precipitate and rate of precipitation relative to fluid convection were important factors that controlled the extent and depth of permeability damage. Cement filtrates that showed fast rates of precipitation tended to damage the upstream end of the core, whereas filtrates with slow precipitation rates tended to plug the downstream end of the core or not plug the core at all. The composition of the cement played an important role in determining both the quantity and the rates of precipitation. For example, the addition of lignin derivatives or polymer reduced the quantity of precipitate and resulted in less damage to the rock. The addition of cellulose derivatives, on the other hand, increased the rate and quantity of precipitation by an order of magnitude and resulted in more damage. [3]

If the depth of invasion of the cement filtrate can be restricted to ≈ 4 in., cement-filtrate-induced damage should not be a major concern, because the perforation tunnels will bypass the damage. However, in some situations in which large volumes of cement filtrate may be lost, this form of damage should be seriously considered. In such cases, the use of fluid-loss-control additives and polymers in the cement slurry needs to be evaluated carefully, so that the cement is properly designed to minimize both the leakoff rate and the amount of insoluble precipitates formed in the formation.

Perforating

The process of perforating is critical to well productivity because the perforation is the only channel of communication between the wellbore and the formation. During underbalanced perforating, the surge flow of fluid into the wellbore should clean the perforation tunnel of all disaggregated rock and liner debris. Any remaining debris in the tunnel could plug gravel packs during production. Even clean perforation tunnels show a narrow region of reduced permeability around them. The nature of this crushed or compacted zone around perforation tunnels created during perforating has been widely studied. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] It is now well recognized that it consists of shattered grains and fines generated by the perforation charge and perhaps fines that flow in from the formation during underbalanced surge flow. The reduction in permeability in the compacted region is typically of the order of 20 to 50% but can be larger in some cases. [27] Using an optimal underbalance pressure results in better perforation performance. [6] The reasons for this are not completely understood. It is likely that too low an underbalance results in insufficient perforation cleaning and too large an underbalance results in the generation and migration of additional fines. This explanation is consistent with the observation that the optimum underbalance pressure is higher for lower-permeability formations.

References

  1. ↑ 1.0 1.1 Cunningham, W.C. and Smith, D.K. 1968. Effect of Salt Cement Filtrate on Subsurface Formations. J Pet Technol 20 (3): 259-264. SPE-1920-PA. http://dx.doi.org/10.2118/1920-PA
  2. ↑ Jones, R.R., Carpenter, R.B., and Conway, M.W. 1991. A Study of Formation Damage Potential During Cementing Operations. Presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, 6-9 October 1991. SPE-22777-MS. http://dx.doi.org/10.2118/22777-MS
  3. ↑ 3.0 3.1 Yang, X.M. and Sharma, M.M. 1991. Formation Damage Caused by Cement Filtrates in Sandstone Cores. SPE Prod Eng 6 (4): 399-405. SPE-19305-PA. http://dx.doi.org/10.2118/19305-PA
  4. ↑ Klotz, J.A., Krueger, R.F., and Pye, D.S. 1974. Effect of Perforation Damage on Well Productivity. J Pet Technol 26 (11): 1303-1314. SPE-4654-PA. http://dx.doi.org/10.2118/4654-PA
  5. ↑ Crawford, H.R. 1989. Underbalanced Perforating Design. Presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-11 October. SPE 19749. http://dx.doi.org/10.2118/19749-MS
  6. ↑ 6.0 6.1 King, G.E., Anderson, A., and Bingham, M. 1986. A Field Study of Underbalance Pressures Necessary To Obtain Clean Perforations Using Tubing-Conveyed Perforating. J Pet Technol 38 (6): 662-664. SPE-14321-PA. http://dx.doi.org/10.2118/14321-PA
  7. ↑ Bartusiak, R., Behrmann, L.A., and Halleck, P.M. 1997. Experimental investigation of surge flow velocity and volume needed to obtain perforation cleanup. J. Pet. Sci. Eng. 17 (1–2): 19-28. http://dx.doi.org/10.1016/S0920-4105(96)00053-8
  8. ↑ Tariq, S.M. 1990. New, Generalized Criteria for Determining the Level of Underbalance for Obtaining Clean Perforations. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 23-26 September SPE 20636. http://dx.doi.org/10.2118/20636-MS
  9. ↑ Behrmann, L.A. 1996. Underbalance Criteria for Minimum Perforation Damage. SPE Drill & Compl 11 (3): 173-177. SPE-30081-PA. http://dx.doi.org/10.2118/30081-PA
  10. ↑ McLeod, H.O.J. 1983. The Effect of Perforating Conditions on Well Performance. J Pet Tech 35 (1): 31–39. SPE-10649-PA. http://dx.doi.org/10.2118/10649-PA
  11. ↑ Suman Jr., G.O. 1972. Perforations-A Prime Source of Well Performance Problems. J Pet Technol 24 (4): 399-411. SPE-3445-PA. http://dx.doi.org/10.2118/3445-PA
  12. ↑ Petitjean, L., Couet, B., Abel, J.C. et al. 1996. Well-Productivity Improvement by Use of Rapid Overpressured Perforation Extension: Case History. J Pet Technol 48 (2): 154-159. SPE-30527-MS. http://dx.doi.org/10.2118/30527-MS
  13. ↑ Halleck, P.M. 1997. Recent Advances in Understanding Perforator Penetration and Flow Performance. SPE Drill & Compl 12 (1): 19-26. SPE-27981-PA. http://dx.doi.org/10.2118/27981-PA
  14. ↑ Hsia, T.Y. and Behrmann, L.A. 1991. Perforating Skin as a Function of Rock Permeability and Underbalance. Presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, 6-9 October 1991. SPE-22810-MS. http://dx.doi.org/10.2118/22810-MS
  15. ↑ Halleck, P.M., Poyol, E., and Santarelli, F.J. 1995. Estimating Perforation Flow Performance From Variations in Indentation Hardness. SPE Drill & Compl 10 (4): 271-275. SPE-24769-PA. http://dx.doi.org/10.2118/24769-PA
  16. ↑ Kooijman, A.P., van den Hoek, P.J., de Bree, P. et al. 1996. Horizontal Wellbore Stability and Sand Production in Weakly Consolidated Sandstones. Presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, 6-9 October 1996. SPE-36419-MS. http://dx.doi.org/10.2118/36419-MS
  17. ↑ Pearson, J.R.A. and Zazovsky, A.F. 1997. A Model for the Transport of Sand Grains From a Perforation During Underbalance Surge. Presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 October 1997. SPE-38634-MS. http://dx.doi.org/10.2118/38634-MS
  18. ↑ Zhang, J., Rai, C.S., and Sondergeld, C.H. 1998. Mechanical Strength of Reservoir Materials: Key Information for Sand Prediction. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 27-30 September 1998. SPE-49134-MS. http://dx.doi.org/10.2118/49134-MS
  19. ↑ Behrmann, L.A., Pucknell, J.K., Bishop, S.R. et al. 1991. Measurement of Additional Skin Resulting From Perforation Damage. Presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, 6–9 October. SPE-22809-MS. http://dx.doi.org/10.2118/22809-MS
  20. ↑ Behrmann, L.A., Pucknell, J.K., and Bishop, S.R. 1992. Effects of Underbalance and Effective Stress on Perforation Damage in Weak Sandstone: Initial Results. Presented at the SPE Annual Technical Conference and Exhibition, Washington, D.C., 4-7 October 1992. SPE-24770-MS. http://dx.doi.org/10.2118/24770-MS
  21. ↑ Bird, K. and Blok, R.H.J. 1996. Perforating In Tight Sandstones: Effect Of Pore Fluid And Underbalance. Presented at the European Petroleum Conference, Milan, Italy, 22-24 October 1996. SPE-36860-MS. http://dx.doi.org/10.2118/36860-MS
  22. ↑ Pucknell, J.K. and Behrmann, L.A. 1991. An Investigation of the Damaged Zone Created by Perforating. Presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, 6-9 October 1991. SPE-22811-MS. http://dx.doi.org/10.2118/22811-MS
  23. ↑ Brooks, J.E., Yang, W., and Behrmann, L.A. 1998. Effect of Sand-Grain Size on Perforator Performance. Presented at the SPE Formation Damage Control Conference, Lafayette, Louisiana, 18-19 February 1998. SPE-39457-MS. http://dx.doi.org/10.2118/39457-MS
  24. ↑ Behrmann, L.A., Li, J.L., Venkitaraman, A. et al. 1997. Borehole Dynamics During Underbalanced Perforating. Presented at the SPE European Formation Damage Conference, The Hague, Netherlands, 2-3 June 1997. SPE-38139-MS. http://dx.doi.org/10.2118/38139-MS
  25. ↑ Halleck, P.M., George, J., and Bast, M. 1999. The Character and Distribution of Damage Around Perforations: Comparison of Balanced and Underbalanced Conditions. Paper presented at the 1999 SPE Eastern Regional Meeting, West Virginia, 20–22 October.
  26. ↑ Venkitaraman, A., Behrmann, L.A., Blok, R.H.J. et al. 1997. Qualitative Analysis of Perforation-Induced Gravel-Pack Impairment Experiments. Presented at the SPE European Formation Damage Conference, The Hague, The Netherlands, 2–3 June. SPE-38144-MS. http://dx.doi.org/10.2118/38144-MS
  27. ↑ 27.0 27.1 Sharma, M.M. 2000. The Nature of the Compacted Zone Around Perforation Tunnels. Presented at the SPE International Symposium on Formation Damage Control, Lafayette, Louisiana, 23-24 February 2000. SPE-58720-MS. http://dx.doi.org/10.2118/58720-MS

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Formation damage

PEH:Formation_Damage

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