| dc.description.abstract | Understanding the connectivity of fluids within a hydrocarbon reservoir is critical to the
viability and effective exploitation of the hydrocarbons present. Establishing reservoir
connectivity using the limited datasets available during the exploration stage of a
discovery is challenging. Whilst numerous tools currently exist to determine static
connectivity and fluid organisation post-hydrocarbon emplacement, it is extremely
difficult to determine the connectivity between fluids in different phases.
Conventional connectivity studies undertaken on the Tormore field, West of Shetland
Basin, UK have resolved the vertical connectivity of one oil well but have been unable to
resolve any further vertical connectivity of the gas wells or the lateral connectivity of
the field. The inert nature of noble gases makes them ideal tracers as they do not react
with or degrade within hydrocarbon reservoirs in the same manner as organic tracers
can. In addition, whilst noble gases are primarily present in the gas phase, they exhibit
predictable partitioning behaviour making them ideal for assessing reservoir
connectivity in both the gas and liquid phase. This research investigatesthe role of noble
gases in resolving vertical and lateral reservoir connectivity and post-emplacement fluid
organisation.
The connectivity of hydrocarbon fluids of the Tormore field is assessed using two
approaches; static and dynamic. The static approach for assessing connectivity follows
the same logic as many conventional industry tools. Given time, a well-connected
reservoir will reach a steady-state equilibrium with a predictable distribution of noble
gases in segregated fluid column across a reservoir. Hence, a disconnected reservoir unit
will have a distinctive set of isotopic abundances and ratios due to their isolation. This
novel noble gas approach independently verifiesthe results of established conventional
connectivity methods and further identifies a previously unknown connection between
two different fluid phases separated by a poorly constrained fault. This approach also provides strong evidence for disconnection between two different reservoir
compartments.
The main limitation for assessing connectivity using a static approach is the lack of ability
to confirm that a connection exists. To address this knowledge gap, a more dynamic
approach using a numerical simulation is investigated. The aim of this numerical
approach is to recreate the major controls of the distribution of noble gases across the
field, from which the lateral connectivity can be resolved. The results of this modelling
demonstrate that the distribution of noble gases in the Tormore field is controlled by
diffusion, proving a lateral connection between the oil and gas phase.
Hence, the novel noble gas connectivity models developed in this work provides a new
method that compliments existing hydrocarbon exploration workflows. This new noble
gas tool provides a robust means to assess reservoir connectivity to constrain the
connectivity between oil and gas phases, where these methods can be applied in the
appraisal phase of a hydrocarbon field. | en |
