Neptune will acquire survey and geotechnical data to help PTTEP decide on export pipeline routing options from the Cash Maple Field, located some 680km west of Darwin, 700km northeast of Broome and 200km south of the Indonesian coastline.
PTTEP has previously been considering both conventional LNG and floating LNG options for the fields.
Neptune's work will be executed from the MV Offshore Guardian which Neptune currently has on long term charter.
The work scope also requires pipeline engineering services which includes pipeline concept design and geohazard reporting, all to be supplied under Neptune's head contract.
Neptune CEO Robin King said the opportunity represented further work for a "valued client" under a relationship which goes back many years, and "demonstrates PTTEPs trust and value in the wide suite of Neptune services which they currently utilise".
The cash Maple facility will produce gas from three groups of fields: the Cash Maple field itself, a southern group of fields comprising Padthaway, Bilyara, Tahbik and Montara fields, and the Oliver field, all of which PTTEP says will require a multi-billion dollar investment.
Drilling from the Cash-2 and Maple-2 appraisal wells in September 2011 and July 2012 provided encouraging results indicating a larger gas resource than previously projected.