(Adds detail, context)
DUBAI, April 22 (Reuters) - A consortium of Gulf-based investors including Fajr Capital and Arab Petroleum Investment Corp (APICORP) have agreed on a deal to acquire Dubai-based oilfield services firm National Petroleum Services, Fajr said on Tuesday.
The transaction, which is expected to close in the second quarter of 2014, is valued "in excess of $500 million", it said in a statement.
Reuters had reported last November that a Gulf consortium led by Fajr and also containing APICORP and Saudi-Arabia based investment holding company Zamil Group were in advanced talks over a deal worth between $500 million and $700 million.
This followed an unsuccessful attempt to sell NPS to Norway's Aker Solutions in 2012.
While Fajr didn't specify how much of NPS the group was buying nor who the selling shareholders were, the statement said some of the current shareholders would retain a minority stake, including Abdul Aziz Al Dolaimi, who would continue as chairman.
In a separate statement to the Saudi stock market late on Monday, Saudi Advanced Industries Co said it was selling its 20 percent stake in NPS for $110 million. It would book a 7.3 million riyal ($1.95 million) loss on the investment due to unrealised profits and investment costs incurred since its initial $100 million investment, the statement added.
NPS chief executive Adnan Ghabris will remain in his role, with the management team unchanged.
The acquisition takes Fajr's assets under management to over $1.2 billion, chief executive Iqbal Khan said in the statement.
Fajr is an investment firm backed by a number of sovereign funds including Malaysian state fund Khazanah Nasional and Abu Dhabi Investment Council. APICORP is a development bank established by the Organization of Arab Petroleum Exporting Countries to invest in the Arab energy sector.
NPS operates in the Middle East, Malaysia, North Africa and Brunei, offering services including oil well servicing and testing.
HSBC and Freshfields Bruckhaus Deringer acted as the sell-side advisers, while the consortium was advised by Simmons & Company and Gibson Dunn, the statement said. ($1 = 3.7503 Saudi Riyals) (Reporting by Bernardo Vizcaino; Writing by David French; Editing by Andrew Torchia)