Mechanical Blocking Devices

Fact Sheet - Mechanical Blocking Devices

   
 
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  Causes of excess water production.
Causes of excess water production; Source: R.S. Seright, Petroleum Recovery Research Center, New Mexico Institute of Mining and Technology

Some wells generate much more water than anticipated. In other cases, the rate of water production suddenly increases.

Two primary technologies can be used to restrict water from entering the well bore: (1) mechanical blocking devices, and (2) chemicals that shut off water-bearing channels or fractures within the formation, preventing water from making its way to the well. This fact sheet describes mechanical blocking devices and technologies. Water shut off chemicals are introduced in a separate fact sheet.

Operators have used various mechanical and well construction techniques to block water from entering the well. Seright et al. (2001) offer several examples of these techniques:

  • Straddle packers
  • Bridge plugs
  • Tubing patches
  • Cement
  • Well bore sand plugs
  • Well abandonment
  • Infill drilling
  • Pattern flow control
  • Horizontal wells

Another technology that can help block water from entering a well is a swellable elastomer packer (JPT 2009). There are two main types of swellable elastomers used for downhole packers - oil or water swelling. Swellable packers combine the advantages of both cement and mechanical packers. The packers themselves are thin sections of swellable rubber that are vulcanized directly onto the.tubing - they swell when they come into contact with the appropriate fluid, water or oil. More information can be found in the Swellfix brochure (undated).

Not all types of reservoir or well construction problems can be effectively mitigated by mechanical devices. When considering water reduction approaches, operators should first diagnose the specific cause of the increased water production. Failure to determine the cause can lead to selecting a solution that does little to correct the problem.

For example, Seright et al. (2001) identify 13 types of events that lead to excess water; these are grouped into four categories describing the most viable remedies. Seright et al. (2001) recommend that mechanical approaches can be used to block leaks in casing or water that flows between the casing and the well bore. Mechanical approaches, however, may not be effective in solving other more complex types of water production problems. For example, when water is leaking through small-diameter pathways in the casing or the formation, cement is not fluid enough to flow deep into the pathways. For these types of water problems, water shutoff gels and gelants may produce a better result.

  Cross-section of a well bore in a formation, showing good and bad configurations.
Cross-section of a well bore in a formation, showing good and bad configurations; Source: Baker Hughes Inc.

The figure shows a downhole oil/water separator. (This technology is described in a separate fact sheet.) For the purposes of this fact sheet, it illustrates two contrasting geologic and well construction conditions. The left side of the drawing shows good cementing and a sound geologic barrier between the oil and water layers. This configuration will minimize the amount of water entering the well. However, on the right side, water production to the well is greatly increased because of: (a) a poor cement job between the casing and the well bore, and (b) the lack of a geologic barrier between the oil and water layers. In the figure, both sources of uncontrolled water flow are relatively large in size. These would be good candidates for the deployment of mechanical blocking devices.


References

JPT, 2009, “Versatile Swelling Packer Tool Provides Reliable and Economical Zonal Isolation,” Journal of Petroleum Technology, “ March, pp. 26-33.

Seright, R.S., R.H. Lane, and R.D. Sydansk, 2001, "A Strategy for Attacking Excess Water Production," SPE 70067, presented at the SPE Permian Basin Oil and Gas Recovery Conference, Midland, TX, May 15-16. [Note that this paper contains a detailed reference list that can point readers to a wealth of relevant literature.]

Swellfix brochure, undated. Available at http://swellfix.net/corporate/brochure.pdf [PDF-external site].

Veil, J.A., M.G. Puder, D. Elcock, and R.J. Redweik, Jr., 2004, "A White Paper Describing Produced Water from Production of Crude Oil, Natural Gas, and Coal Bed Methane," prepared by Argonne National Laboratory for the U.S. Department of Energy, National Energy Technology Laboratory, Jan. Available at http://www.evs.anl.gov/pub/dsp_detail.cfm?PubID=1715.

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