Enhancing Karstified Carbonate Characterization Through Focused Seismic Reprocessing and Machine Learning Utilization in Ubadari Field

Abstract

Ubadari is an undeveloped gas field in Bintuni Bay (West Papua, Indonesia) about 70km west of the Tangguh LNG plant. Seismic reprocessing (2015 and 2018) and appraisal well results (2019) elevated the field from option to the main project of Tangguh Expansion phase 2. The development plan will require several development wells from one or two platforms and a dedicated pipeline to supply gas to the 3rd Tangguh LNG train. The previous seismic reprocessing projects in Ubadari were focused on improving the reservoir image and the imaging in the overlying karstified carbonate remained suboptimal. Given the magnitude of drilling problems associated with this karstified Faumai formation and the role of seismic data in identifying the karst features (Birt, 2015; Riangguna, 2016; Birt, 2019), a seismic reprocessing with the focus on the overburden was required. bp completed the latest Ubadari seismic reprocessing in 2021 to identify the overburden drilling hazards that may impact the platform numbers and location. The seismic reprocessing resulted in step improvements of the overburden imaging although it was still highly masked by the karsts. Therefore, seismic attributes using the rapid interpretation Machine Learning-based tools were utilized to remove interpretation biases and improve the confidence level. The major faults in the carbonate can now be extracted and identified as having interaction with the older fault system on the reservoir level. The faults also formed a long span of collapse system on the very shallow carbonate section. The typical karst system in Tangguh (known as discrete circular bright troughs amplitude features) was also identified along or near the faults. This robust overburden characterization and drilling hazards assessment were delivered on time to be part of key consideration in the screening and optimization of the Ubadari future platform location for the TEP phase 2 project.