SPG India 2023

3-5 November 2023 |  LBICC Kerala, India

November 4: Unveiling potential: Opportunities and challenges in E&P sector amidst changing energy landscape | Panel session

November 5: Keynote presentation: Exploring Frontiers | Session: TS 18

Keynote presentation: Exploring Frontiers

Optimising use of a multi-client dataset through post-migration prestack gather conditioning and interpretation – an Indonesian case study

Abstract

David Jessup, Premier Oil Andaman Ltd – A Harbour Energy Company, Dave Goulding, Andy Kalil and Adrian Smith, Sharp Reflections

Multi-client seismic datasets typically provide a lower cost opportunity to gain insight into the subsurface, compared to proprietary seismic surveying. The business model is for one or more oil companies to commit to licensing the data, with ownership remaining with the acquirer. This mitigates some of the risk on investment in a region, especially high in frontier areas. The value to the oil companies includes the acquirer having an understanding of the petroleum system in place, as well as the obvious cost saving through partnership. The compromise here is the relinquishment of full control over the survey parameters, processing and its targets. Key to the investing oil companies is the appropriateness and quality of the data for their exploration program. Reservoir focused acquisition and processing is challenged when these surveys cover many thousands of square kilometers and depths of thousands of meters. One such survey was licensed from PGS by Harbour Energy and covers an area of the Andaman Sea in Indonesia.

Harbour Energy had identified several amplitude-supported exploration prospects using the multi-client 3D seismic dataset. Following the application of full volume pre-stack seismic health checks, observations of sub-optimal event alignment, noise level and bandwidth, at the target level, gave rise to concerns about pre-stack amplitude fidelity and the data’s suitability for quantitatively evaluating the prospects. The aim of this study was to provide reservoir-focused, quality assured pre-stack gathers and derivative attributes to aid exploration drilling planning. The team used iterative full-volume QC attributes at each step of the conditioning process to assist with algorithm parameterization and to address spatial and temporal variations in data quality. Interpretation of the results was assisted through extensive 3D synthetic modelling of possible reservoir, seal and fluid scenarios, utilizing data from offset wells to identify key Extended Elastic Impedance (EEI) angles for reservoir and fluid prediction.

The workflow resulted in improved amplitude fidelity across the volume, specifically in terms of event alignment, noise and bandwidth consistency; with Class IIp events clearly preserved and even enhanced. The resulting AVA attributes and EEI volumes demonstrated enhanced resolution of the pre-stack signal and allowed Harbour Energy to confidently calibrate the observed responses against pre-drill scenarios. The successful, play-opening discovery well was drilled by Harbour Energy in Q2 2022, providing valuable calibration for pre-stack inversion work to follow.