By Shanti S Nair and Ron Bousso
Dec 11 (Reuters) - Oil and gas producers could wipe billions of dollars more off the value of U.S. natural gas assets in the months ahead, analysts said on Wednesday, after Chevron Corp became the fourth oil major to slash its estimates for sector values.
A long, steady increase in U.S. gas production – much of it a byproduct of the shale oil boom – has pushed prices for the fuel heading toward a 25-year low and a number of analysts have already forecast that the oversupply will worsen in 2020.
Prior to Chevron's impairment, BP PLC, Repsol SA and Equinor ASA had written down billions worth of North American shale assets in recent months.
Chevron on Tuesday said it expects to take writedowns to the tune of $10 billion to $11 billion in the fourth quarter, more than half of which is related to its Appalachia gas shale assets. Shares of the company were down 0.7% at $117.04 in early trading.
It also flagged a cut to its longer-term commodity price outlook without specifying numbers, and said it was planning to sell some natural gas projects.
"It ... highlights that many companies are still carrying assets on their balance sheet that were acquired or developed with cost structures that are materially higher than today's levels," Berenberg analysts Henry Tarr and Ilkin Karimli said.
BP Plc said in its 2018 annual report that it determines the size of its recoverable oil and gas reserves based on a long-term Brent oil price of $75 a barrel and a Henry Hub natural gas price of $4 per mmbtu.
European peer Shell has also long expected improvement in prices and forecast in its 2018 annual report that Henry Hub natural gas prices would rise to $3.50 in 2020 and 2021 from $3.25 per mmbtu in 2019.
Benchmark gas prices are currently around $2.28 and Morgan Stanley analysts on Wednesday lowered their forecast for next year to $2.25 from $2.50.
Spain's Repsol last week recorded a 4.8 billion euro ($5.29 billion) asset loss, primarily on its North America assets. BP took a $3.3 billion charge in the third quarter with $2.3 billion relating to heritage shale assets from the BHP portfolio it acquired last year for $10.5 billion.
Norway's Equinor wrote off $2.8 billion in the third quarter, while Exxon Mobil Corp took a $2 billion charge in 2017 against the value of natural gas reserves from its buyout of XTO Energy.
"The pricing companies have to use for reporting their proved reserves are on pace to be around 15% lower than last year, so I'd expect reserve write-downs to be prolific," Edward Jones analyst Jennifer Rowland said. ($1 = 0.9073 euros) (Reporting by Shanti S Nair in Bengaluru and Ron Bousson in London; Editing by Anil D'Silva)