HIGHLY DEVIATED WELLS

In perforating highly deviated (more than 60°) or horizontal wells, certain factors are considered, including positioning of the guns, cost of the perforating process depending upon the length interval, the oil water contact and encroachment of water due to high drawdown pressure. The cost increases with the interval length, which will also affect other factors like shot density, high performance charges, etc. This could therefore be avoided by locating the best zones in the interval with high porosity, oil saturation, and pressure, which can be done by using logging tools and then perforating the desired zone.

Usually in horizontal wells it is preferred to focus on a certain perforation area, rather than perforating the whole interval, which may cause wellbore breakdown or collapse;

however, this decision is still under observation according to many past field results. This localization of a certain area is extremely helpful in initiating a fracture leading to a network of multiple fractures. According to some deviated wells field performance (King, 2007), perforating at 8-16 spf in a 2-5 ft. interval is enough to initiate a fracture.

The decision to select a perfect perforating strategy involves choosing the above factors correctly and efficiently according to the requirements and formation conditions.

Different strategies for the optimal and clean perforation have been put forward by

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various oil and gas companies. One of them, as shown on the next page, has been used by company Schlumberger for last ten years.

Figure 5.7: Perforation Technique Selection Strategy by Schlumberger (Cosad, 1992)

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CHAPTER 6 CONCLUSION

 With the empirical/theoretical equations discussed in Chapter 3, not only can the optimum underbalance pressure be calculated at almost no damage, but it also helps in predicting the skin from perforation damage if optimum underbalance pressure is not possible.

 Emerging perforating techniques and methods like dynamic underbalance perforation made it clear that effective perforation cleanup and improved productivity depends not only on the intial applied pressure conditions but also on the early transient underbalance produced during perforation. This dynamic underbalance can be controlled and prolonged by using special methods like canisters with specific volume (can be adjusted) attached with the gun, by controlling the detonation gas pressure and by adjusting the internal volume of the gun. However, this technique has been only discussed for consolidated formations, and not for formation prone to sand production with low reservoir pressure. For that extreme overbalanced perforation was considered and proved to be quite successful.

 Extreme overbalance is also a useful choice for perforation, and, according to the field examples discussed, it has played a critical role in the increment of production when underbalance was not possible. However, it has some limitations, like the length of the fracture before turning towards the preferred fracture plain, the number and their conductivity, how long can they remain open, etc. These are the questions which are still under investigation.

 Significant increases can be seen in productivity by utilizing the test data and field experience for the effective shot density and perforation length. Production is a function of shot density, but it has a limit depending upon the casing rating and can be unsuccessful for intervals having anisotropic permeability. Shot density is preferred over perforation diameter due to the fact that increasing diameter gives very

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minute increase in the productivity. Perforation length can be predicted nowadays by using special computer programs based on the lab tests reducing time and cost.

 During the selection of the perforation strategy, phasing is one of a key element for the optimal flow rate production, which is selected depending upon the conveyance, formation characteristics, and diameter of the casing & tubing. 90 degree phasing usually has the highest effect in the increase.

 Charge type also has a special role in successful perforation. By the selection of the efficient explosion, conveyance method, and with the advancement in the completion technology, the goal to have the optimal productivity can be achieved; however, the cost factor has to be considered.

 From the review it can be concluded that tubing conveyed perforation is much better than the wireline because of its ease to perforate a long interval simultaneously in a single trip without making multiple runs on a wireline, and at the same time with the use of drill Stem testing, testing can be done on the spot for a long period of time

In order to achieve the objective of perfect perforation, one has to analyze and evaluate the available reservoir data and design the job. Normally the common mistake encountered is to bypass the above process and repeat the same thing that was considered in the last job. This approach often works, but sometime it also leads to some significant failures. By taking both the field data and operating experience under consideration, the operator will be able to apply what was successful in the last job and prevent errors.

72 CNR International, Aberdeen, Scotland, Salsman, A., Walton, I., Rosharon, Texas, USA, Lloyd Stutz, Anadarko Petroleum Corporation, Houston, Texas, David Underdown, Chevron Texaco, Houston, Texas, “The New Dynamics of Underbalance Perforating”, Oilfield Review, Volume 15, 2003.

 Bellarby, J. “Well Completion Design”, Volume 56, SPE, 2009

 Behrmann, L.A., Pucknell, J.K., Bishop, S.R. and Hsia, T-Y: “Measurement of Additional Skin Resulting From Perforation Damage,” paper SPE 22809, presented at the 66th SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, October 6-9, 1991

 Behrmann, L.A., Li, JL, Venkitaraman, A. and Li, H.: “Borehole Dynamics During Underbalanced Perforating,” paper SPE 38139, presented at the SPE European Formation Damage Control Conference, The Hague, The Netherlands, June 2–3, 1997.

 Behrmann, L.A., Huber, K., McDonald, B., Rosharon, Texas, USA, Benoit Couet, Ridgefield, Connecticut, USA, Folse, R., Marathon Oil Company, Lafayette, Louisiana, USA, Dees, J., Consultant, Pat Handren, Oryx Energy, Dallas Texas, Schmidt, J., ARCO Alaska, Inc., Anchorage, Alaska, USA, Snider, P., Marathon Oil Company, Houston, Texas, “Quo Vadis, Extreme Overbalance?”, Oilfield Review, Volume 8, 1996.

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 Behrmann,L.A., Khong, C.K., “The Search for Perfect Perforations”, Middle East &

Asia Reservoir Review, Volume 7, 2006

 Behrmann, L.A., Brooks. J.E., Farrant, S., Fayard, A., Venkitaraman, A., Rosharon, Texas, USA, Brown, A., Michel, C., Noordermeer A., BP Amoco, Sunbury on Thames, England, Smith, P., BP Amoco, Houston, Texas, Underdown, D., Chevron Production of Technology Company, Houston, Texas, “Perforating Practices That Optimize Productivity”, Oilfield review, Volume 12, 2000.

 Behrmann, L.A., McDonald, B., Schlumberger Wireline & Testing: “Underbalance or Extreme Overbalance”, SPE 57390, August 1999.

 Bell, W.T.: “Perforating Techniques for Maximizing Well Prodxutivity." paper SPE 10033 presented at the SPE International Pet. Exhibition & tech. Symposium, Beijing, China, March, 1982.

 Bell, W.T.: “Perforating Underbalanced – Evolving Techniques”, SPE paper 13413, October 1984.

 Bell, W.T. & Bell, R.M. :"The Paradox OF Gun powder vs Completion Efficiency,"

Explosives Conference of IADC, Houston, June 9-11 1981

 Blosser, W. R., 1995. “An Assessment of Perforating Performance for High Compressive Strength Non- Homogeneous Sandstones”. SPE 30082.

 Bruyere, F., Total E&P UK plc, Kusumadjaja, A., Balikpapan, Indonesia, Manalu, D., Sobririn, M., Total E&P Indonesie, Balikpapan, Indonesia, Martin, A., Robertson, D.I., BP, Stenhouse, A., Consultant, Aberdeen, Scotland, Clark, D., Stirton G., CNR

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International, Aberdeen, Scotland, “New Practices to Enhance Perforating Results”, Oilfield Review, Volume 18, 2006.

 Brown, J. A., Zemla, J., Calgary, Alberta: “Method of Completing & Producing Hydrocarbons in a Well”, US 6173783, January 16, 2001.

 Cased Hole Log Interpretation Principles/ Application, Schlumberger, Fourth printing, March 1997.

 Cuthill, D. A., De Winton, C.A.: “Method & Apparatus for Perforating a Casing &

Producing Hydrocarbons”, US 7571768, August 11, 2009.

 Grove B., Heiland, J., Walton I., Atwood D.; “New Effective-Stress Law for Predicting Perforation Depth at Downhole Conditions”, SPE 111778, SPE Drilling &

Completion Volume 24, Pages 678-685, December 2009.

 Halleck, P.M. and Behrmann, L.A: “Penetration of Shaped Charges in Stressed Rock” in Hustrulid WA and Johnson GA (eds.): Rock Mechanics Contributions and Challenges: Proceedings of the 31st US Symposium. Rotterdam, The Netherlands:

A.A. Balkema (1990): 629-636.

 Hsai, T-Y & Behrmann, L.A., "Perforating Skin as a Funtion of Rock Permeability and underbalalnce" paper SPE 22810, presented at the 66th SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, October 3-6, 1991.

 Halliburton Perforating Solutions Manual, Halliburton

 Halleck, P.M., Terra Tek Inc.; Saucier, R.J., Behrmann, L.A., Ahrens, T. J. ;

“Reduction of Jet Perforator Penetration in Rock Under Stress”; SPE 18242, presented at the 63rd Annual Meeting of the SPE, Houston, 1998.

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 Javora, P.H., Ali, S.A. and Miller, M. : “Controlled Debris Perforating Systems:

Prevention of an Unexpected Source of Formation Damage,” paper SPE 58758, presented at the SPE International Symposium on Formation Damage Control, Lafayette, Louisiana, USA, February 23-24, 2000.

 Jaeger, J.C., Cook, N.G.W., “Fundamentals fo Rock Mechanics (3rd ed.)”, New York Halstead Press (1979)

 Johnson, A.B., Behrmann, L.A., Yang, W., Cornells D.F.H.: “Controlling Transient Underbalance in a Wellbore”, US 6732798, May 11, 2004.

 Lake, L.W., Editor in Chief, University of Texas, Austin and King, G. E., BP plc, 2007, “Petroleum Engineering Handbook”.

 Locke, S., Schlumberge-Doll Research: “An advanced method for predicting the productivity Ratio of a Perforated well”, paper PE 8804, presented at the SPE 4^th Symposium on Formation Damage Control, Bakersfield, CA, Jan., 28-29, 1981.

 Michael, K. Robson, 1990, “Introduction to and Benefits of Tubing Conveyed Perforating”, SPE Paper 19109.

 Minto, D., Falxa P., Manalu, D. and Simatupang, M., Total E&P Indonesie and Behrmann, L.A., SPE, Kusumadjaja, A., SPE, Schlumberger, “Dynamic Underbalanced Perforating System Increases Productivity and Reduces Cost in East Kalimantan Gas Field: A Case Study”, SPE/IADC 97363 paper has been presented at the SPE/IADC Middle East Drilling Technology Conference & Exhibition held in Dubai, U.A.E., 12-14 September 2005.

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 Pucknell, J.K., BP Research, and Behrmann, L.A., Schlumberger Perforating & Test Centre : “An Investigation of the Damage Zone Created by Perforating”, SPE 22811 presented at the 66th Technical Conference and Exhibition of the Society of Petroleum Engineers held in Dallas, TX, October 6-9, 1991

 Ratanasirigulchai, W., Behrmann, L.A., Martin, A.J., Goodman, K.R., Schlumberger Reservoir Completions: “Controlling Transient Pressure Conditions in a Wellbore”, US 2004/0231840, November 25, 2004.

 Schlumberger Well Performance Manual, Schlumberger

 Seibi, A. C., Boukadi, F. H., Salmi, S. & Bemani, A.: “Mathematical Model for Estimating Perforation Penetration Depth”, Petroleum Science and Technology, 26:15, 1786-1795.

 Smith, P.S, Behrmann, L.A., Yang, W.: “Improvements in Perforating Performance in High Compressive Strength Rocks”; SPE 38141, presented at SPE European Formation Damage Conference, 2-3 June 1997, The Hague, Netherlands, June 2-3.

 Subiaur, S.T., Graham, C.A. and Walton, I.C.: “Underbalanced Criteria for Perforating Carbonates”, paper SPE 86542, presented at the SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, USA, February 18–20, 2004

 Van Den Hoek, P.J., Kooijman, A.P. and Kenter, C.J., Koninklijke/Shell E&P Laboratorium, and Khodaverdian M., Hylan, C.R., and McLennan, J.D., Terra Tek Inc.; “Size-Dependency of Hollow Cylinder Collapse Strength”, SPE 24800 24 was presented at the 67^th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers held in Washington, DC, October 4-7, 1992

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 Walton, I.C.: “Optimum Underbalance for the Removal of Perforation Damage”, paper SPE 63108, presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, October 1–4, 2000.

 www.GEKEngineering.com: By George E. King, Professional Engineer, Petroleum Engineering

 Walton, I.C. Johnson, A.B., Behrmann, L.A. Atwood, D.C.; "Laboratory Experiments Provide New Insights into Underbalanced Perforating"; SPE No. 71642, presented at SPE Annual Technical Conference & Exhibition, Sep. 30-Oct. 3, 2001; pp. 1-8.

 Yew, C.H. & Zhang, X, U of Texas: “A Study of the Damage Zone Created by Shaped-Charge Perforating”, SPE 25902 was presented at the SPE Rocky Mountain Regionall Low Permeability Reservoir Symposium held in Denver, CO, U.S.A, April 12-14, 1993.

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APPENDIX A TYPES OF GUN FIRING HEAD AND