Upstream oil and gas firm Coro Energy has upgraded resource estimates for the Mako gas field, offshore Indonesia.

Operator Conrad Petroleum prepared the report, assessing the 1C (contingent) resource at 323 billion cubic feet (bcf) of recoverable raw gas. This represents an increase of 76% on the pre-appraisal estimate of 184 bcf in the previous Gaffney Cline and Associates (GCA) review.

The assessment has ascribed gross 2C resources of 493 bcf, and gross 3C resources of 666 bcf.

The original assessors are currently conducting a new independent reserves audit for the field.

Revised development scenarios are under review, and these could lead to plateau production of 150MMcf/d, much higher than the previously modelled 44MMcf/d.

The Mako gas field lies in water depths ranging from 60m to 100m. The field is part of the Duyung production sharing contract (PSC), located in the West Natuna basin. It is an extremely large, shallow structural closure of more than 350km², and has excellent seismic definition with direct hydrocarbon indicators.

It is also located close to the West Natuna pipeline system.

Coro holds a 15% non-operating interest in the Duyung PSC. Remaining partners are Conrad (76.5%) and Empyrean (8.5%).

According to the company, previous success at Mako saw the Tambak-1 and Tambak-2 wells in the final quarter of last year demonstrate the presence of well-developed, high quality reservoir sandstones across the structure.

In March last year, Indonesia’s Ministry of Energy and Mineral Resources (MEMR) approved the plan of development (POD) for the Mako gas field.

In February the same year, Coro Energy signed an agreement to acquire a 15% direct interest in the Duyung PSC.