An issue with coiled tubing-based pinpoint stimulation for multizone fracturing has been that large-diameter coiled tubing was required to achieve the high rates and fluid volumes, velocities and downhole pressures required for perforating and fracturing. The 2-3/8-in. or 2-7/8-in.-diameter coiled tubing imposed depth limitations due to the additional weight and the reel capacity of conventional coiled tubing units. Fortunately, recently developed technology has eliminated these shortcomings.

CobraMax® H Service Provides Coiled Tubing Efficiency and Optimized Frac Treatments
CobraMax® H service enables operators to benefit from the efficiency of coiled tubing-based multi-zone fracturing while optimizing key fracturing treatment parameters for both vertical and horizontal wellbores:

  • Injection rate
  • Proppant volume
  • Proppant concentration

Innovative Aspects
The service combines hydrajetting-assisted fracturing with the coiled tubing’s well control capabilities and speed to provide several innovative features:

  • Enables perforating and fracturing in the same trip in the hole
  • Eliminates the need to set mechanical plugs that must be removed later – proppant slug provides necessary diversion to upper zones
  • Enables the use of conventional coiled tubing units, typically 1-3/4-in. or 2-in. OD units
  • All operations are on a live well

Specifications

  • No temperature limits with the bottomhole assembly (BHA)
  • No depth limitations, except for the reach of the coiled tubing
  • Enables fracturing in casing sizes of 3-1/2-in. or greater
  • No downhole packer or bridge plug to manipulate

CobraMax H service is especially beneficial for horizontal wells where the process helps achieve higher production rates by eliminating flow convergence from the fracture into the wellbore. The proppant pack as a final stage of each fracture treatment helps achieve maximum conductivity in the near-wellbore region where flow convergence issues are the most extreme.

CobraMax H Service Provides 30 Percent Improvement in 180-Day Post-Frac Cumulative Production

Chevron began using the CobraMax H process in January 2005 in the Lost Hills field in California. The CobraMax H process began in 2004 and became the sole stimulation technique in 2005 after side-by-side comparisons. The surface and downhole tiltmeter analysis was used to compare the limited entry fracturing technique vertical coverage to the CobraMax H service vertical coverage. The CobraMax H technique has shown a 30 percent increase in the vertical fracture coverage compared to limited entry. A comprehensive report of the study is documented in SPE 101840 which spans two years’ history in the use of the CobraMax H process.

The study found that the use of CobraMax H service to place an average of 18 fracture treatments per well resulted in a 30% improvement in 180-day post-frac cumulative production as compared to the 18-stage “perf and plug” fracturing method used prior to the introduction of CobraMax H service. As a result, the cost per BOE for completions costs was reduced by almost half, which resulted in an expansion of the field development due to favorable economics. As of September 2006, more than 100 CobraMax H service completions have been performed in the Lost Hills field. The development project is entering Part 4 expansion and CobraMax H service remains the sole method of completing these wells.

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