(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. Reuters had reported last **vember 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 0 million and $700 million. This followed an unsuccessful attempt to sell NPS to **rway's Aker Solutions in 2012.