Lengo gas field is a planned offshore development in the East Java Sea, Indonesia.

The Government of Indonesia approved the Plan of Development for the field in 2014. The Final Investment Decision (FID) is expected to be taken in the second quarter of 2024, with first gas anticipated in 2026-2027.

In December 2022, Criterium Energy signed a binding agreement with a subsidiary of Mitsui E&P Australia Holdings (MEPAU) to acquire a 42.5% non-operated working interest in the Bulu Production Sharing Contract (PSC), which contains the Lengo gas field.

As a result of the deal, Criterium became a 42.5% holder of the Bulu PSC through a wholly owned subsidiary and AWE(Asia). Other stakeholders are Kris Energy (Satria) (42.5%), Satria Energindo (10%) and Satria Wijaya Kusuma (5%).

Lengo Gas Field location details

Lengo gas field is located within Bulu PSC in shallow waters around 65km offshore of East Java. Water depth at the site is around 50m.

The Bulu PSC, located adjacent to East Muriah PSC, encompasses an area of around 697km2. It includes three separate areas Bulu A, Bulu B and Bulu C in the East Java Basin.

The Lengo gas discovery is situated in the Bulu A area.

Appraisal and Geology

The Lengo gas field was discovered in 2008 by the Lengo-1 well.

The well was drilled on the flank of the structural closure to a total measured depth of 959m.

Lengo-1 penetrated a 142ft gas column on the flank of the structure in the Miocene Kujung 1 formation and flow tested 12.9 million standard cubic feet per day (scf/d) (methane 65% with 12% CO2 and 20% N2).

In 2013, the Lengo-2 appraisal well was drilled using Shelf Drilling’s Randolph Yost jack-up rig to confirm the commercial volume of the gas in the discovery as well as to assess a secondary target in an overlying reservoir within the greater Lengo closure.

Located 3.3km south-west of the Lengo 1 well in 57m water depth, Lengo-2 was a vertical well that had a planned total measured depth of 830m. The Lengo-2 well flow tested 20.6 MMscf/d.

Two separate drill stem tests (DST) were also carried out to assess the reservoir productivity for the upper section of the Kujung 1 formation and the overall Kujung 1 carbonate sequence.

The first DST tested the upper part of the Kujung I formation and flowed gas at a rate of 4.5 million scf/d, while the second DST achieved a gas flow rate of 21.2 million scf/d.

The top Kujung carbonate reservoir was confirmed to be at approximately 700m true vertical depth sub sea (TVDSS) and a gross gas volume of 70m. It was identified as a high-quality carbonate reservoir with an average porosity of 26%.

The Kujung reservoir is a mid to lower Miocene carbonate build-up at a depth of approximately 700m. It features an upper red algal zone and lower reefal zone in pressure communication.

Lengo field gas reserves and field development

Lengo field hosts an estimated gross un-risked 2C recoverable gas resource of 359 billion cubic feet (bcf), of which 134bcf is net to Criterium.

The development plan approved by Indonesian authorities in 2014 comprises four development wells and an unmanned wellhead platform.

The recovered gas will be exported through a 20-inch, 65km long pipeline directly to an Onshore Receiving and Processing Facility (ORF).

Carbon dioxide present in the gas will be removed to meet pipeline specifications. Carbon sequestration options are also being explored to reduce environmental impacts.

The field is estimated to produce 60 – 80 MMscf/d gross at plateau.

Gas sales agreement

In August 2022, the Bulu PSC partners signed a Heads of Agreement (HOA) with an industrial end-user in East Java. The gas is expected to be supplied to current infrastructure and/or upgrades to existing facilities.

The binding gas sales agreement (GSA) is expected to be signed in the fourth quarter of 2023.

Contractors involved

PT Synergy Engineering conducted the FEED study for the Lengo field. The company conducted the Reliability, Availability and Maintenance (RAM) Study for the field development. This included the production and utility systems essential for production availability.

The independent assessment of Criterium’s Contingent Resources in the Lengo gas field Bulu was completed by Netherland, Sewell & Associates (NSAI).