* Listed companies slashed production by 2.4 pct in Q3
* Declines follow sharp spending cuts in face of downturn
* OPEC struggles to hammer out deal on output cut
* GRAPHIC: http://tmsnrt.rs/2g3yCP5
By Ron Bousso
LONDON, Nov 24 (Reuters) - The world's listed oil companieshave slashed oil output by 2.4 percent so far this year duringone of the industry's worst downturns as OPEC battles to agreeon its first production cut since 2008.
The aggregated production of 109 listed companies thatproduce more than a third of the world's oil fell in the thirdquarter of 2016 by 838,000 barrels per day from a year earlierto 33.88 million bpd, data provided by Morgan Stanley showed.
By comparison, the Organization of the Petroleum ExportingCountries produced 33.64 million bpd in October. OPEC hasstruggled to agree on a joint production freeze or cut tosupport oil prices before its Nov. 30 meeting inVienna.
In the second quarter of 2016, the companies reducedproduction by nearly 930,000 bpd, according to Morgan Stanley.
The firms include national oil champions of China, Russiaand Brazil, international producers such as Exxon Mobil and Royal Dutch Shell, as well as U.S. shale oilproducers like EOG Resources and Occidental Petroleum.
The drop in oil companies' output is particularly compellinggiven the increase in 2015, when third-quarter production roseby some 1.9 million bpd.
"Clearly, we have seen a large swing in the year-on-yeartrend in production, from strong growth as recent as a year ago,now to steep decline. This is the outcome of the strong cutbacksin investment," Morgan Stanley equity analyst Martijn Rats said.
Capital expenditure for the companies combined more thanhalved from $136 billion in the third quarter of 2014 to $58billion in the same period this year, according to Rats.
Oil executives and the International Energy Agency have warned that a sharp drop in global investment in oil and gaswould result in a supply shortage by the end of thedecade.
Large oilfields, such as deepwater developments off thecoasts of the United States, Brazil, Africa and Southeast Asia,typically take three to five years and billions in investment todevelop.
Cost reductions and increased efficiencies have only partlyoffset the drop in production as a result of the lowerinvestment. Technological advancements have also helped boostonshore U.S shale production.
"These declines should temporarily soften in 2017 as newfields are coming on-stream in Canada, Brazil, the former SovietUnion and U.S. tight oil probably stabilises," Rats said.
"Still, unless investment rebounds relatively soon, thissteep downward trend is likely to resume in 2018 and beyond."
(Reporting by Ron Bousso; Editing by Dale Hudson)
