HOUSTON — When it comes to extending the life of mature fields, the Norwegian North Sea is perhaps one of the best places to look if in search of revitalization tricks.

“The North Sea has many older fields. I believe we have some new and maybe more old tricks that can keep these producing fields producing properly for many more years,” Tim Dodson, executive vice president for Statoil, said April 21 during the IHS Energy CERAWeek conference.

Older fields can become technically challenging, potentially becoming costly burdens. Today’s low oil-price environment puts such fields at risk, considering they are also competing against greenfields for dollars. However, most operators are not giving up on older fields as different techniques and technology add volume.

Statoil aims to use all acquired data, including well and seismic data, to devise new concepts.

“One example is broadband seismic, which has the potential to provide increased resolution or clearer images of the subsurface in shallow areas and enhance our geological understanding,” Dodson said. “We are not only looking deeper. We are looking shallower.”

The company, which has already increased its average recovery factor from 30% to 50% in Norway but is targeting 60%, also calls itself the pioneer of 4-D seismic monitoring technology. Dodson used Statoil’s Gullfaks Field as an example. Gullfaks, located in the northern part of the Norwegian North Sea, was discovered in 1978. But in the last 10 years, he said Statoil has drilled 19 wells there based on 4-D seismic data and has added more than an estimated $1 billion in value.

Gullfaks has a recovery factor of 59%, but Statoil is pushing for 62%, according to Statoil’s website. A subsea multiphase compressor, delivered in March by OneSubsea, for the Gullfaks South Field could increase the recovery rate for the Gullfaks South Brent reservoir by 22 MMboe.

Other tricks to ramp up recovery include horizontal and extended-reach wells, water alternating gas injection and new completion and sand-control technology.

“The best place to find more oil is where oil has been found. This is why we continue to have such a strong presence in the North Sea,” Dodson said. “The Norwegian Shelf has been revived over the last few years. We believe there is a potential to do the same in the U.K. as geology has no border.”

In addition to increasing recovery, other ways to survive the pain of lower oil prices is to adopt a proactive maintenance approach, improve equipment reliability and lower well costs. Leaner designs, standardization and meticulous planning are among Statoil’s methods.

“Work on mature fields is absolutely essential for us if we want to meet our objectives,” added Michel Hourcard, senior vice president, Americas, for Total.

Mature fields need technology whether the goal is to:

  • Bring new production from nearby prospects or undeveloped reservoirs to existing facilities.
  • Optimize and accelerate production of declining fields with techniques such as new subsea compression or fracking conventional reservoirs.
  • Improve recovery through reservoir management and other EOR or IOR methods, according to Hourcard.

To extend the Aguada Pichana Field in Argentina, Total used a combination of techniques that included increasing compressor capacity and fracking of tight gas. Initial 2P reserves in 1994 of about 1.2 Tcf grew to about 2.5 Tcf by year-end 2014, Hourcard said.

But the problem with mature fields is sometimes high costs, making field efficiency important. Current market conditions also call for being selective to control cash spending, and larger scale redevelopments might be decided based on a longer-term view of oil and gas prices, he said.

“We have to maintain or increase 2P reserves as much as we concentrate on new projects,” Hourcard said.

Field abandonment is uncommon in the industry, added Leta Smith, a director for IHS. Of all of the fields that have produced outside onshore and shallow-water North America, only about 24% have been abandoned or temporarily shut-in, she said, adding, “If you take a stricter view, it goes down to 13%.”

For larger fields, abandonment is even less common. She presented statistics that revealed between 3% and 8% of the larger fields, those with more than 20MMbbl, have been abandoned.

“This is really a testament to the value of new tricks or old tricks” for mature fields, she said.

Other old, low-quality conventional reservoirs, such as fields in the Granite Wash, Delaware Sands and Sprayberry in the U.S., are being revitalized with unconventional techniques.

“The conventionals typically have shorter lateral length and fewer frack stages. That right off the top makes them, generally speaking, less expensive,” compared to shale wells that utilize the same techniques, Smith said.

In addition, not using fracture stimulation for horizontal wells in conventional plays cuts cost. That was the case in frack-free France’s St. Martin de Bossenay Field, which was abandoned by an operator in the 1990s but resurrected by another operator in 2005 with non-fractured horizontal wells. Instead, “They went back into the vertical wells and did horizontal sidetracks,” Smith said, noting that at 9 MMbbl the field was small but its reserves increased to 10 MMbbl. “This isn’t going to be material enough for many operators, but a 10% improvement in recovery factor is substantial.”

Contact the author, Velda Addison, at vaddison@hartenergy.com.