With rigs in short supply offshore as well as on land, the cost of intervention to bring back a well crippled by water invasion places a heavy hand on a producer’s wallet. But swellable elastomers offer an opportunity to let equipment in the hole handle the chore without expensive intervention.

The job is expensive enough when an operator of an onshore field has to bring in a drilling

S-ZIP packers work on intelligent and multilateral wells. (Graphics courtesy of Swellfix Zonal Isolation)
rig or workover rig for intervention work. Offshore situations are hundreds of times more expensive when the operator has to pay mobilization charges on top of high day rates for a floater to work on a well in deep water. The value proposition is higher offshore because the cost of intervention is higher.

The chief advantage of swellable elastomers, according to John Dewar, chief executive officer of Shell Technology Ventures Swellfix Zonal Isolation, is that, “You don’t need a team of people to intervene. Just put it in the right place (in the well’s completion string).” The swellable packers do their jobs automatically, with one exception.

Swellable elastomers
Swellable elastomers are no longer the new technology in town. The company’s zonal isolation systems have been around for more than 6 years with more than 3,000 joints installed in working wells without a single failure. Tests on more than 2,000 elastomer-rubber compounds tailor the tools for working conditions in any well. Those tests should cover nearly every situation imaginable, but realistically, about 10 compounds will handle most applications found in the oilpatch.

Dewar was head of Shell expandables when he first started research into swellable elastomers. Metal expandables were fine in lot of situations, but wellbores aren’t always round, and a product that could expand in water or in oil could provide a new sealing tool in the production engineer’s toolbox.

Now the company has a series of products designed for most applications.
• I-ZIP (zonal inflow profiling) is a scab liner run inside manufactured liner. When water invades the liner, the I-ZIP swells to seal off perforations that allow water invasion. In the late life of a well, they also can shut off water flow at the end of a string.
• E-ZIP fits around tubing or liner in an open hole to shut off water outside the production tubing.
• X-ZIP is designed to fit outside expandable tubulars to provide a better seal against losses and help promote borehole stability.
• S-ZIP seals isolate branches of multilateral wells in smart-well applications. Packers are grooved to allow control wires and cable to pass through.
• C-ZIP fits around the outside of conventional casing joints. It often provides a pressurized seal around the casing where cement may fail, or it may replace a cement squeeze.
• G-ZIP fits around the outside of conventional gravel-pack screens in horizontal wells to block fines migration above the screen.

The S-ZIP is the only application that isn’t fully automatic. Because of the smart-well set-up, a crew has to come to the well site to set up the packer.

With those expandable products available, Dewar added, “Why cement? Why run liner? Why perforate? Just keep the hole with the pressure-set line, swellable packers and liner packers?”

For the future, Dewar envisions operations in which the producer just drills a horizontal hole, skips the cementing step and sections the hole with expandable packers. “Everyone I’ve spoken to agrees it’s a good idea,” he added.

The company plans to introduce five new products this year to deal with frac jobs, running flatpacks, high-pressure/high-temperature applications, lost circulation and through-tubing rigless completions.

Solutions follow challenges
Solutions follow challenges, and Shell had some big challenges at more than 2,000 wells it operated in cooperation with Petroleum Development Oman (PDO).

Shell conducted some of the first field trials at its operations in Oman where water breakthrough in fractured limes created a real production problem, Dewar said.

The company ran its E-ZIP swellable packers in 2003 across faults in the formation in Nimr field in southern Oman. The packers expanded to slow water and allow oil to flow more freely. “In every case, oil production was up at least three times,” he said.

Before the installation, one well in southern Oman produced 107 net b/d of oil with a 90% water cut. Following the installation and the long-term swelling of the packers, oil production climbed to a maximum of more than 1,258 b/d of oil, and water cut dropped to 22%. Eleven of 15 wells first tested averaged two to three times more oil production.

Now a standard completion for the company in Oman involves installation of seven to 10 E-ZIP joints per well.

The operating company also tested expandable tubulars with X-ZIP swellable elastomers as a backup for zonal isolation in Yibal field in northern Oman. That application was so successful that the company decided to try a 3,281-ft (1,000-m) long horizontal well fitted with X-ZIP elastomers on expandable pipe to isolate water-producing zones.
That successful trial set a record as the longest openhole clad and openhole liner installation with swellable elastomers.

The company had more than 2,000 wells in Oman. Swellfix tailored the elastomers to fit individual well fluid and downhole conditions, and every installation worked.
“The competition has one elastomer for all, but North Sea oil swells different than Middle East oil,” he said.

The testing process has produced a range of products with extreme flexibility that can swell up to 600% in volume and 100% in thickness in days or weeks, depending on the needs of the operator and downhole conditions. Once set in place, the elastomer seals will hold tight against the formation or tubing as long as the swelling agent is present.

If a packer swells in the presence of oil, that swelling may recede a little if an influx of water follows the oil, Dewar said.

If the operator needs to hold higher pressures, it can add more packer bands to the tubing, he added. For example, 13 bands could hold 13,000 psi of downhole pressure.
The only restriction on the sealing capacity of the packer is when its swelling range is exceeded by the annular space. It can conform to out-of-round holes and fill in rough spots in solid rock.

Swelling
A rough guide to swelling ranges depends on downhole conditions. In an oil-swelling situation, light oil will expand the elastomers more than heavy oil, and high temperatures offer more swelling potential than low temperatures.

In a water-swelling environment, low salinity gives an operator more swelling potential than high salinity. And, as with oil, high temperatures expand the elastomers more than low temperatures.

Elastomers in condensate can expand nearly 900% to maximum size in about 2,400 hours, while Middle East oil might allow them to swell only about 600% in 3,700 hours. West Africa oil would expand the elastomers less than 400% in the same time period.

To date, the company has delivered products with operators in Colorado in the United States, the United Kingdom, Denmark, Nigeria, Sudan, Cameroon, Russia, Malaysia, Brunei and New Zealand.

It is working with operators for future work in the Gulf of Mexico, Brazil, Egypt, Azerbaijan, Kuwait, Indonesia, the Philippine Islands and Australia.

Now the only manufacturing plant for the swellable products is the Ruma plant in Holland. For the future, Swellfix plans to open a plant in Houston to locate manufacturing close to operations, and it may open a Middle East manufacturing facility.

The company plans to move its operations base from The Hague to Aberdeen as well. “There’s one oil company in The Hague. There are 50 in Aberdeen,” Dewar said.

Also for the future, his ideal outcome for the company would be to set up global contracts with service companies. That would allow the company to offer the products to everyone at the same price.