Use of the first ever ISO V0 certified gravel-pack packer enabled quick, reliable completion of three critical, high-volume gas wells — the highest producing gas wells for a BP-operated field worldwide — without need for additional production packers.

High-rate gas producing wells operate from the Cannonball platform, the first offshore platform to be designed and constructed in Trinidad and Tobago, to supply feed gas to the Atlantic LNG Train 4 production facility. (Photo courtesy of BP and Schlumberger)

Eliminating the production packers also eliminated the associated costs of purchase, testing and installation, and two of the three wells were completed several days ahead of the completions authority for expenditure (AFE) timetable.

Many factors contributed to the success of this project, but three of the key factors are:

  • Thorough planning and systems integration testing (SIT) provided a robust system, which minimized likelihood of incidents stemming from completion design;
  • Use of the ISO V0 certified gravel-pack packer as a combination gravel-pack/production packer; and
  • Use of alternate path technology to provide alternate flow paths in pumping operations, maximizing the likelihood of achieving a complete pack.

Project background

The Cannonball field was developed by BP Trinidad and Tobago (bpTT) to provide feed gas to Atlantic liquefied natural gas (LNG) Train 4. As such, these wells were deemed “business critical” because they fulfill contractual requirements for the LNG feed.

Located off of the southeast coast of Trinidad, 22 miles (35 km) off of Galeota Point, in water depths of 231 ft (70 m), the formation is about 280 ft (85 m) thick with high permeability and porosity. The reservoir properties include a formation pressure slightly higher than 6,400 psi and temperature of 220°F (104.4°C) at 12,350 ft (3,764 m) total vertical depth.

The high rock strength at the reservoir would have allowed a sand face completion of the wells without any type of sand control, but because of the extremely high rates at which the wells would be producing, any sand production, even small quantities, would be catastrophic for both the completion hardware and the surface equipment.

Previously, in similar gas fields, bpTT had good experience and success using openhole gravel pack (OHGP) sandface completions with no additional production packer; this approach had proven reliable for ensuring relatively low skin values and providing corresponding flow efficiencies. Support of the LNG train schedule made maximum efficiency of utmost importance for this drilling and completion project, so the solution had to be as simple as possible with a standardized completion design for all three wells.

Solution overview

So an OHGP without a production packer was also chosen for the Cannonball wells. However, because these wells were of such critical business importance, the operator’s well team decided it was necessary for the packers to be rated V0, the highest possible rating for a packer per industry standard ISO 14310.

At the time of equipment selection in early 2004, there was no 10 3/4-in. gravel-pack/production V0 rated packer on the market. However, the Schlumberger 10 3/4-in. by 6-in. QmaX Packer was nearly through the extensive ISO 14310 qualification process that would designate it V0. This fact, coupled with the criteria to keep the upper completion “as simple as possible,” lead the wells team to decide to use the QmaX Packer in the primary completion design.

In addition, one of the main requirements to use the newly qualified packer was that it be qualified together as a gravel-pack system consisting of the 10 3/4 by 6 in. packer, the OHGP anti-swab gravel-pack extension, and the anti-swab service tool (ASST). At the time, this system had never been used in conjunction with the new packer and gravel-pack extension. Consequently, a successful SIT was a must before the OHGP system could be approved for use on Cannonball.

Two SITs were performed between the end of 2004 and early 2005. Some problems were encountered during the first test, which resulted in the use a new wellbore cleanout string during the second test. The second test was successful and the system qualified, and the operator decided to use the same tools for the actual project.

V0 certified gravel/production Packer

ISO Standard 14310 defines requirements for packers and bridge plugs used in the petroleum and natural gas industry and provides that selected nominal characteristic for packers be defined. The standard provides seven qualification levels, ranging from a low of V6 to a high of V0.

To qualify for a V0 rating, a packer undergoes rigorous testing for axial loads, temperature cycling, and a gas test that must meet a “zero bubble criteria.” Pressure is applied both above and below the packer with gas, while the packer is cycled through hot and cold temperatures. The packer cannot leak any gas past the element to earn the V0 rating as a production packer.

Alternate path technology

Alternate path technology (APT), a system of screens and shunt tubes, provides alternate flow paths in pumping operations and maximizes the likelihood of achieving a complete pack. Many believe that circulating water packs are enough to achieve a complete pack. But based on prior testing and experience with the technology in Trinidad and the need for operational longevity of these business critical wells, the operator chose to use APT for all three wells.

Execution and results

On the first well, CAN-01, problems occurred when attempting to set the packer, so it was pulled out of the hole and inspected. Within 48 hours, the investigation team determined that a carbonate plug in the wash pipe prevented the packer from setting. The team determined that neither the service company nor the packer was responsible for this problem; therefore, a back-up assembly was run and the job completed successfully, as designed.

The program was modified to include a more thorough cleaning of the openhole interval to minimize recurrence of this problem. Also it was decided that the gravel-pack logging tools, which provided invaluable troubleshooting data, would be run for all future openhole gravel packs. In addition, shunt tube action was observed towards the end of the gravel pack thereby reinforcing the importance of their use.

On the second well, CAN-02, the APT paid dividends with almost 50% of the gravel pumping job completed through the shunt tubes. Because of a larger rat hole below the casing shoe resulting from the drilling technique used, a sand dune formed then collapsed when it reached critical mass, causing a premature screen out. The shunt tubes performed as designed and the well was completed 5 days below AFE.

The third well, CAN-03, had both problems observed in the first two wells, the wash pipe plugging and the rat hole with early screen-out issues. But the lessons learned, best practices and overall project design successfully addressed those issues and CAN-03 was completed 8 days below AFE.

Cost savings

The Cannonball completion project ended below Completions-AFE cost and time with 16.2% non-productive time during the completion phase (14% attributed to the plugged wash pipe event on CAN-01). The majority of savings was realized because CAN-02 was completed 5.09 days below Completions-AFE and CAN-03 was completed 8.07 days below Completions-AFE, resulting in cost savings of approximately US $1.25 million ($250,000/day (rig time) by 5 days) and $2 million ($250,000/day by 8-days), respectively.

In addition to the benefit the operator can claim by having three wells capable of performing up to their full potential, using the V0 certified packer resulted in further cost savings by eliminating the need for the following equipment:

  • Production packer, including a backup;
  • Pup joints;
  • Assembling cost;
  • Test cost;
  • Cost corresponding to the time to make-up (about 1 hr) and set (about 2 hr) this packer, which at an approximate rig rate of $250,000/day or $10,416.67/hr comes to 3 hr x $10,416.67/hr = $31,250; and
  • Cost for third party inspection services.

Total approximate cost savings for one well was $266,868, and for the three-well project, $800,604.