Mako gas field lies in the Duyung PSC in the West Natuna Basin offshore Indonesia. Credit: Conrad Petroleum.
The Mako Gas Field was approved by the Indonesian government in March 2019. Credit: Conrad Petroleum.
Mako South-1 well is the fourth well to be drilled in the gas field. Credit: Conrad Petroleum.
West Natuna Exploration has submitted a plan of development (POD) for the Mako gas field project. Credit: Conrad Petroleum.

The Mako gas field is located in the Duyung production sharing contract (PSC) in the West Natuna Basin off the shore of Indonesia, in water depths ranging from 60m to 100m.

The Duyung PSC is 100% owned by West Natuna Exploration (WNEL), which itself is jointly owned by Conrad Petroleum (90%) and Empyrean Energy (10%).

Coro Energy signed an agreement to acquire 15% interest from WNEL in the Duyung PSC contract for $4.8m in February 2019. Coro Energy will also invest $10.5m in the 2019 drilling campaign in order to secure its 15% stake in the project.

WNEL submitted a plan of development (POD) for the field in August 2018 to Indonesia’s oil and gas regulator SKKMigas.

The plan of development (POD) was approved by the Indonesian Ministry of Energy and Mineral Resources in March 2019.

Mako gas field location

The Mako gas field lies in the Duyung PSC of the West Natuna Basin, which is considered one of the largest and most prolific proven hydrocarbon basins in Asia.

The Duyung PSC covers an area of 1,145km² and is strategically located approximately 20km from gas export and oil production facilities.

Mako gas field geology and reserves

The Mako gas field is a large gas accumulation covering 340km² of the Duyung PSC, located at a depth of 1,700ft.

The field reservoir lies in a large north-east to south-west elongated anticline, which is 47km long and 16km wide.

It contains sandstones within the Intra Muda formation of the Plio-Pleistocene age.

The field is estimated to contain 705 billion cubic feet (bcf) of gas initially in place (GIIP), with an upside potential of 1,317bcf.

The proven and probable recoverable gross 2C and 3C resources are estimated to be 276bcf and 392bcf respectively, as per the independent report carried out by Gaffney Cline & Associates in early 2019.

Appraisal of Mako gas field

The Mako gas field has been appraised by three wells, namely Cakalang-1, Tenggiri-1 and Mako-1, which established the presence of gas and examined the field’s petrophysical characteristics.

However, the three wells themselves were not flow tested.

A fourth well, Mako South-1, was drilled in June 2017 to a total depth of 1,707ft by the COSL Seeker jack-up rig.

The well encountered 23ft of net pay in the Intra Muda formation.

It was tested and flowed at the rate of 10.9 million cubic feet per day with high-quality gas containing 100% methane.

The gas showed no presence of contaminants such as CO2 and H2S.

Mako gas field development details

The Mako gas field is planned to be developed using vertical wells.

Developers have signed a heads of agreement with a regional utility for the sale of the entirety of the gas produced at the field.

A gas sales agreement (GSA) is planned to be negotiated between WNEL and the regional utility, which will finalise the terms of the arrangement.

The final investment decision and GSA are expected to be completed by the second half of 2019.

WNEL is also expected to sign agreements for access to the West Natuna Transport System, which will enable the transportation of gas recovered from the field to Singapore.

Future development plans for Duyung PSC

WNEL completed the re-processing of 2009 2D seismic data to identify the various geological features under the Mako gas field.

An evaluation of the data identified the Mako Deep exploration prospect at depths between 2,000ft and 6,000ft.

Mako Deep is expected to contain large quantities of recoverable oil and gas reserves, along with sand packages similar to those encountered by the Tenggiri-1 well.

Further seismic analyses and examinations of the drill cutting recovered from the Tenggiri-1 well are currently underway in order to delineate and de-risk the prospect.

The prospect is planned to be drilled in September 2019 to examine its potential.

Contractors involved

Indonesia’s state-owned research and technology institution Lemigas was awarded a contract to certify the field’s reserve estimates, as well as provide assistance for the preparation of the POD.

COSL Drilling provided its COSL Seeker drilling rig for the drilling of the Mako South-1 appraisal well.