Well-considered perforation strategies can enhance mature field production

Using an optimized hydraulic fracturing perforation strategy to maximize production may increase cash flow by accessing missed pay. (Hull, 2015)

Well-designed perforations are vital to a well’s completion because they are the connection between the wellbore and the formation. To avoid cuts to incremental production, operators should consider the challenges involved in correctly perforating. For example, maintaining high static differential pressure (underbalance) is required to prevent destruction of the formation, as crushed rocks produce a low permeability zone and create the potential for fines to flow into the wellbore. To avoid these and other issues, it is important to understand complex reservoir conditions, especially those that are encountered in mature fields. Complex reservoir conditions such as overburden stress, wellbore/reservoir pore pressure and well/formation response to downhole temperature can decrease the effectiveness of a well’s perforation if not completely understood.

Figure 1: Difference between Halliburton MaxForce Frac charge and a commercial grade charge. MaxForce is more effective in creating equal-sized perforations.

Getting the maximum perforation zone correct is crucial to optimizing access to the most productive zone of the reservoir. For example, the original design for a hydraulic fracturing treatment may have one central perforation per zone, which is not optimal because more perforations may be needed. In addition, maintaining equal perforation hole size will ensure an equal frac length and distribution of treatment flow. Uneven perforations can often be caused by using the wrong charges, and typically occur in horizontal wells where the charge rests on the casing floor.

The solution to challenges such as these is a perforation design that is tailored to an operator’s current formation and reservoir conditions from day one, in order to get it right the first time and avoid costly adjustments. MaxForce™ shaped charges and frac charges, used in demanding well conditions, can by-pass near wellbore damage and improve well productivity. This is made possible by the ability of MaxForce to deliver custom charges targeting specific reservoir/wellbore problems and ensure perforation holes are of equal diameter (see Figure 1).

SurgePro™ software can identify the optimal combination for specific reservoir conditions and design an effective dynamic underbalanced perforation solution for maximum clean-up. Used in conjunction with MaxForce™ charges, SurgePro™ can optimize a perforation solution for the best results.

As an example, one particular operator was looking for a cost-effective wireline solution to perforate in a horizontal well. Halliburton recommended using MaxForce™ shaped charges to produce more even entry holes regardless of gun position (Figure 1). A comparison of similar wells showed an additional 4,600 pounds of proppant per stage could be placed.

Halliburton has presented additional new ideas to operators, such as propellant-assisted perforation to enable an effective stimulation diversion equally across the entire perforating interval, and as an alternative to acidizing. Fracture lengths are equal from each perforation tunnel, working particularly well in karstic carbonate systems where natural fractures can be connected to provide an excellent permeability network. This enables perforation and stimulation to be completed at the same time.

In summary:

  • Getting perforating strategy right the first time can save the cost of having to re-perforate, and reduces the need for costly screen-outs (Robinson et al, 2008). It is important to know the conditions of your reservoir and simulate different perforation assemblies to predict how they will react down-hole, thus preventing formation collapse.
  • Equal-sized perforation holes are important to allow an equal flow of treatment and equal fracture length to exploit the maximum productive zone.

References

Hull, R., 2015. Back to the Future? Article in E&P, published October 2015.

Robinson, F., Folse, K., Brinsden, M. and Wong, D., 2008. Propellant Assisted Perforating – An Alternative Stimulation Solution in Heavily Karstified Carbonate Reservoirs. International Petroleum Technology Conference, IPTC 12334-PP.

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