3D Thermobaric Modelling of Central Spitsbergen - Implications for Gas Hydrate Occurrence

Author: Peter Betlem
Year: 2018
Supervisors: Kim Senger, Einar Jón Ásbjörnsson and Juliet Ann Newson

Abstract

Gas hydrates have traditionally been viewed as hazardous to petroleum operations, particularly with respect to flow assurance in pipelines and slope stability. They occur where gas migrates through environments characterised by moderate pressures and low temperatures. Gas hydrates thus naturally occur in two main settings, i.e., a deepmarine, offshore setting and a polar, onshore setting associated with permafrost. While nowadays considered a vast potential source of hydrocarbons, stability of gas hydrates in the permafrost setting is being compromised by climate change, with release of even a small fraction of the permafrost-associated hydrates being potentially hazardous. Exploration and quantification of Svalbard's gas hydrate potential is limited compared to other polar regions (e.g., Russia, Alaska, Arctic Canada), even though the archipelago's unique setting makes it even more prone to change. By designing a semi-automated workflow, and incorporating all available data, this work has resulted in the first assessment of the gas hydrate stability zone (GHSZ) for central Spitsbergen. The framework's Python back-end allows for both laterally and vertically changing input parameters, is easily upgradable with both new functions and novel datasets, and provides a link to third-party tools while guaranteeing industry-standard support through Schlumberger's Petrel front-end. Although uncertainties in local temperature and pressure regimes prevent higher-order assessments, a strong correlation is observed between GHSZ and base permafrost. On a regional scale, the vertical extent of the GHSZ is most pronounced in areas with thick layers of permafrost, i.e., highlands and mountains, with the lateral extent governed by trends governing surface and subsurface thermobaric conditions. In Adventdalen, intrapermafrost heterogeneities, wet gas and pressure built-up near the base permafrost, and borderline favourable thermal regimes, make for a likely gas hydrate formation setting. Changes in surface temperature are likely to destabilise a substantial part of the regional GHSZ. The versatility of the workflow has furthermore been shown via an offshore GHSZ modelling effort targeting the Fingerdjupet Subbasin, SW Barents Sea, through a collaboration with the operating company Spirit Energy.