May 1 (Reuters) - Shale producer Diamondback Energy Inc reported first-quarter profit below Wall Street estimates on Monday, hurt by lower prices of crude, sending its shares down 2%.

Global crude prices averaged $82 a barrel in the January-March quarter, down nearly 16% from a year earlier as concerns about global economic outlook weighed on prices.

The Midland, Texas-based firm said total average unhedged realized prices were $49.72 per barrel of oil equivalent in the reported quarter, 29% lower from a year earlier.

Its average production was 425,022 barrels of oil equivalent per day (boepd), higher than 381,378 boepd last year.

Diamondback also said there were signs that inflation, which plagued the industry in recent quarters, is showing signs of abating.

"We believe well costs peaked over the last two quarters and have line of sight to meaningful decreases in the upcoming quarters," Chief Executive Travis Stice said in a letter to investors.

Stice added that raw materials and service costs are declining and he expects his company's completion costs to be lower.

The company sees second-quarter production at between 430,000 and 436,000 boepd and capital expenditure increasing to a range of $675 to $725 million.

"The Q2 guidance was a little bit better on production than expected. Capital expenditure is a little bit higher in Q2, but that was a timing issue," said Gabriele Sorbara, an analyst at Siebert Williams Shank & Co.

Diamondback also reaffirmed its full-year forecast for net production and capital expenditure.

The company said in February it was increasing its non-core asset sale target to at least $1 billion by the end of this year from $500 million.

On an adjusted basis, the company earned $4.10 per share in the quarter, compared with estimates of $4.33, according to Refinitiv data. (Reporting by Arshreet Singh and Liz Hampton; Editing by Maju Samuel)