Refracking brings ‘vintage’ oil and gas wells to life

Horizontal Drilling Rig in Weld County Colorado - Credit Niobrara News

Horizontal Drilling Rig in Weld County Colorado – Credit Niobrara News

By Anna Driver and Ernest Scheyder – Reuters – Wed Aug 20, 2014

NORTH DAKOTA Aug 20 (Reuters) – A fracking boom isn’t enough for U.S. oil and gas producers – they’re now starting the re-fracking boom.

Wells sunk as little as three years ago are being fracked again, the latest innovation in the technology-driven shale oil revolution. Hydraulic fracturing, which has upended global energy markets by lifting U.S. crude oil output to a 25-year high, has been troubled by quick declines in oil and gas output.

The development highlights how producers must constantly invest and tinker, both to raise overall oil recovery rates that can be as low as 5 percent and to limit steep drops in production suffered by wells drilled into tight oil deposits. (Related: See Decline Curves of the Niobrara)

Canada’s Encana Corp invested $2 million to refrack two wells in Louisiana’s Haynesville shale formation earlier this year, after seeing its production in the area dip 27 percent from 2012 levels.

“There were a significant number of wells that we considered understimulated,” said David Martinez, Encana’s senior manager for Haynesville development.

Using minuscule plastic balls, known as diverting agents, pumped at high speeds with water into the old wells, most of which are three to five years old, Encana blocked some the older fractures, or cracks.

“The thought is that the diverting agent will go to the cracks with the least amount of pressure,” bypassing cracks with higher pressure and boosting the pressure of the entire well so output climbs, Martinez said.

He said the process can’t be as precisely controlled as an initial round of hydraulic fracturing, in which water, chemicals and sand into are blasted into rock to unlock oil and gas.

Fracking has been used on about 1 million wells bored since 2007, and oil and gas companies now fracture as many as 35,000 wells each year, according to FracFocus, the national fracking chemical registry.

Continue reading story at Rueters

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