PESA NSW October 2026 Technical Lunch: Horizon Oil

Sinphuhorm & Nam Phong Gas Fields, Northeast Thailand

In August 2025, Horizon Oil and Matahio Energy acquired ExxonMobil’s interests in the Sinphuhorm and Nam Phong gas fields, located on the Korat Plateau in northeastern Thailand. Nam Phong, now operated by MH Energy Thailand, the local Thai entity established by Horizon Oil and Matahio Energy, is the older of the two fields and has been producing gas since the 1980s. Sinphuhorm, discovered later, commenced production in 2006 and is operated by Thailand’s national oil company, PTTEP. Together, the fields supply gas to the Nam Phong Power Plant, which provides a significant portion of the electricity demand across northeastern Thailand.

The regional geology comprises a thick succession of Triassic to Cretaceous continental clastic sediments overlying Permian carbonate platforms, which form the primary reservoirs in both fields. Deposited in a warm, shallow marine environment, these carbonates have undergone multiple phases of diagenesis, tectonic fracturing, and dissolution. Subsequent episodes of extension and structural inversion exposed carbonate highs to prolonged meteoric and burial dissolution, creating an extensive network of caves, vugs, and collapse breccias. Later tectonic deformation further enhanced reservoir complexity through the development of fracture systems, resulting in highly heterogeneous reservoirs characterized by a combination of structural and diagenetic porosity.

As relatively new entrants to these assets, Horizon and Matahio are leveraging PTTEP’s extensive operational experience and subsurface knowledge to accelerate understanding of the fields. A key challenge is integrating seismic attributes, well data, and production performance to better characterize reservoir architecture and predict reservoir behaviour. This integrated approach is particularly important for identifying and optimising future infill drilling opportunities within these fractured and karstified carbonate systems.

Ongoing work is focused on translating the geological complexity of the reservoirs into a robust subsurface framework that improves reservoir prediction and reduces development uncertainty. By combining geological, geophysical, and production data, the current work aims to support more confident field development decisions and enhance the long-term gas deliverability of both Sinphuhorm and Nam Phong.