Gone fishing

Elaine Maslin speaks with OTC spotlight award winner Fishbones about the company’s new Dreamliner technology aimed at increasing accuracy and efficiency in reservoir stimulation.

Fishbones’ stimulation completion technology. Images from Fishbones.

The Norwegians like fish – it’s in their blood, it’s on their breakfast table and now it’s even in their oilfield tool kit.

Well, almost. Stavanger-based Fishbones this summer performed the first field trial of its new second generation Fishbones stimulation-completion technology, called Dreamliner, offshore Norway. In 2014 and 2015, the first onshore trials of first generation Fishbones technology was performed in the US.

Fishbones is a multilateral stimulation technology, which uses small diameter titanium “needles,” which are pushed out into the reservoir to increase exposure to the production zone. It is targeting conventional carbonates and tight sandstones, not shales, with two versions created to suit both of those environments. Fishbones for carbonates uses acid jetting and the Dreamliner tool for tight sandstones uses small turbines to spin drillbits on the ends of the needles to penetrate the reservoir.

Fishbones, led by former Baker Hughes’ VP Eirik Renli, won an OTC Spotlight on Technology award earlier this year. Late October, Renli presented the technology to a Society of Petroleum Engineers event in Aberdeen.

Eirik Renli

“Fishbones is integrated into the liner and creates lateral channels like small wells lateral to the main wellbore,” he explains. “Fishbones is the original jetting technology, with 12m-long needles and a nozzle at the front, which jets acid to push the needles out creating laterals. In tight sandstone, the jetting will not puncture the reservoir so we developed another product, Dreamliner, which uses drilling technology.”

With the Fishbones acid jetting, 1m-long Fishbones subs, each with four needles, each secured by a pressure shear mechanism, are pre-installed onto the 11m long regular liner joints being used in the reservoir. It is run into the open hole as part of the lower completion. Standard liner hangers are set together with Fishbones’ in house developed anchors, preventing lateral movement of the liner. A shoe closing mechanism is activated, acid is then pumped into the completion and as the flow increases the pressure across the needles shears the release mechanism, freeing the needles. The needles then press against the rock, jetting a pathway forward. Jetting continues until all needles are fully extended. The well is allowed to produce through the annulus and all the needle annuli.

With the Fishbones acid jetting, Fishbones has developed a “Fish Basket,” which can run down the hole and clear out the remaining ends of the needles so tools can still be run down hole.

For the Dreamliner, each sub contains three needles, secured by a drill through mechanism. Each drill bit is driven by a turbine powered by the main flow through the liner. Again, they’re installed onshore before being run in an open hole. It is design so anchors can be run in between the joints to avoid temperature elongation of the completion. When the string is in position, the liner hanger slips are set and the anchors are positioned then set by flowing into the well.

Fishbones’ Dreamliner.

The flow is increased, which bursts the disc in the casing shoe and, as the flow increases, the turbines and needles reach the working rpm. Rotation releases the needles from the drill through bits and they then push into the reservoir, with some 25kilo force from the flow. Pressure responses during drilling indicate full extension of the needles. Cuttings powder is circulated out of the lateral and up the mother bore to surface. Once the needles are fully out, the liner hanger element is set sealing the annulus. The liner hanger setting tool is pulled and the upper completion is run and the well is allowed to produce. Production occurs in the annulus and all the needle annuli.

Fishbones is looking at ways to remove the turbines and needle ends from open hole so intervention operations and tooling can be run.

One of the benefits of using the needles, or Fishbones technology, instead of a traditional acid stimulation job is that there is more control over how far the stimulation goes into the reservoir, enabling the operator to avoid nearby gas or water zones, Renli says.

The technology, which has been in development since 2009, was trialed for the first time offshore this summer, on Statoil’s Smørbukk South Extension field, near the Asgard field in the Norwegian Sea. It is a tight sandstone reservoir, estimated to contain 16.5 MMboe, but previously deemed non-commercial due to the tight formation, low permeability and porosity ranging from “bricks to tiles,” according to Statoil.

A dual-lateral production well with about 5200m reservoir exposure was drilled, targeting a 30m-thick oil bearing formation above a depleted gas reservoir. Horizontal barriers exist within the sand formation, limiting vertical flow. One of the laterals had the Dreamliner treatment. A 5½in Dreamliner completion with 48 fishbones subs, each with three needles, was installed in the 8½in open hole, creating 144 mini-laterals, spaced across selected zones targeted for stimulation.

In addition, Resman chemical tracers are being used – these are installed along the casing before it is run and are released according to pre-determined criteria, which means the operator can analyze the production, find the chemicals and know from which part of the well, and so reservoir, the production came from.

Renli says the operation appears to have been a success. Statoil has likewise hailed the project a success and said it would be looking where else it can use the technology. However, production data has not been revealed.

Prior to the Smørbukk South application, Fishbones had trialed the Fishbones system in an onshore coalbed methane well in Indonesia. The system installed correctly but issues with a downhole pump meant full results were not gained. Through a project supported by the Joint Chalk Research Group, consisting of Shell, BP, Total, Maersk Oil, Hess, Eni, Statoil, ConocoPhillips, Dong and the Danish North Sea Fund, the Fishbones jetting tool has also been trialed twice onshore Texas in hard Austin chalk and tight fractured limestone – both on horizontals. In the first, 60 laterals were created from a 4½in completion with 15 Fishbones subs, each with three needles, in a 6½in open hole mother well bore. While it was a low-producing well, at just a few barrels, production was increased by a factor of 4 to 5 times, over 30 days, says Fishbones. The firm is hoping to get another pilot well run through the joint research group.

Fishbones has also created a simulation tool which enables operators to input well data to see if their well would be suited to this technology.

Renli is pleased with the results so far and hopes production data from Smørbukk South will validate this new technology.