A tool less tripped
  from: Offshore Engineer
  by: Jennifer Pallanich
  Monday, April 07, 2008

A new completion system isolates multiple zones in a single trip. Jennifer Pallanich talks to one company that adapted its existing isolation equipment to meet operator requests for speeding up the process.

Decreasing time spent on tripping in and out of hole on multizone completions came down to decreasing trips.

'The operators came to us looking for the ability to treat multizones in a more cost-effective manner,' says David Walker, BJ Services' director of completion tool technology, who was involved in developing the MST system. 'The more trips an operator has to make, thatfs just dead time. It's time they could spend doing more productive things.'

To meet operators requests, he says, BJ adapted existing zonal isolation equipment into the ComPlete Multizone Single Trip (MST) system.

'We've developed a system where you can run multiple zones of completion equipment in a single trip, and the system allows you to selectively and individually complete each one of those zones in a single trip in the well,' Walker says. 'Designing a service tool that provides positive position indication during treating operations was really the key.'

BJ designed the tool for multizone treatment so it can run through multiple zones in up and down directions and features a high pressure sealing system. He says the system allows an operator to maintain zone selectivity before, during and after treatment for production. It also gives the ability to provide selective or commingled production.

For each zone, the tool contains isolated gravel pack screens with integral production sliding sleeves, a frac pack/gravel pack sleeve for placing sand or proppant, and an isolation packer. The crew assembles all the zones at the rig floor and individually pressure tests each zone to insure integrity after assembly. A single gravel pack service tool is installed below the lowermost screened interval and connected through a concentric inner workstring to the primary workstring above the top production packer.

The entire assembly is run into the wellbore in a single trip. The service tool contains shifting tools that selectively open or close the production sliding sleeves and frac pack sleeves in each zone allowing zones to be individually treated, then re-isolated. Once all zones are completed, production is run and the zones can be selectively produced by opening or closing the production sliding sleeves located in each interval.

BP tested the concept on two onshore wells in 2005 and 2006, and BJ refined the design based on details learned during the test phase,Walker says. This year, the system has been deployed offshore in four wells. So far, the system has been used in four-zone wells, but he says five- and six-zone wells are planned by the end of 2007.

In the first two wells offshore Indonesia,Walker says, the system saved the operator over four days of rig time compared to the expected duration of a normal dual completion:

• one trip for tubing-conveyed perforating, which saved 24 hours per well;
• one trip for packer plug retrieval, which saved 12 hours per well; and
• one trip running in and locating the frac pack assembly, which saved eight hours per well.

In the second well offshore Indonesia, he says, high-rate water packs were completed on four zones of interest in 35 hours of rig time.

In a Gulf of Mexico well, perforation guns were run below the MST tool to further decrease nonproductive time. Walker says the operation was successful but required two runs: after perforating, the bottomhole assembly was retrieved from the well and a deburring run was made across the perforated intervals. The MST system was redressed, and the well successfully completed with one zone frac packed with 21,000lbs and one with 25,000lbs of gravel as planned.Well production met operator expectations, Walker says.

Over the course of two years, BJ has refined the system and tool, including some dimension changes on the tool itself. The real key, he says, is in the seal and locating technology.

'Providing those seals and locations at each zone gives you the ability to do an almost unlimited number of zones in a single trip,' Walker says. 'The way this works is that you get a new set of seals and new indication point with each zone.'

The application is particularly useful, he says, if there are multiple reservoirs contacting a single wellbore, so smaller zones that would be uneconomical on their own can be completed.

Walker says on typical completions, operators will likely save 25-60%, depending on the number of zones.

The amount of sand that the tool can take before erosion wears it out limits zones. These tools,Walker says, can pump 1 million pounds of proppant with no issues. The lower tertiary in the Gulf of Mexico may require pumping 3 million pounds, which would require tripping the tool, he says. They are available for both 7 5/8in casing and 10 3/4in casing.

‘Of the candidate wells we’ve looked at, there are only one or two where we’ve said we don’t have the correct pressure balance to run the system,’Walker says.

A constraint to the system is that the zones need to be of similar bottomhole pressures because they would be perforated at the same time and left open, Walker says.

‘It’s going to be a very good thing for the industry, to be able to control three, four, five zones, open and close as needed. It should make these completions much more attractive, especially with the more difficult reservoirs that are out there,’ he says.

Walker envisions future systems as integrating smart technology in the form of remotely actuated downhole flow control devices with the system. OE

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