Gas to Wire Or Gas to Shore: Evaluation of Transitional Clean Energy in Offshore UKCS
Authors: Mistry Lisa , Wahid Fazrie , Fitch Peter 
Published: October 2020

Gas to Wire (GTW) is a concept which will aid the UK to meet their growing energy demand as, GTW will allow marginal and somewhat depleted gas fields to convert natural gas to electricity onsite, with the electricity exported via subsea power cables - the concept is not yet fully commercialised offshore. This paper initially discusses what is GTW and then investigates two separate cases: the first focuses on evaluating the viability of GTW for the Kumatage gas field which is 78 km close to shore (located in the Southern North Sea) (Figure A1), by assessing the fields production potential and profitability. The second case will evaluate a standard practice of gas sales. Reservoir data was provided by the company who own the field. The first case was split into three stages. The first stage reviews the sensitivity analyses completed to generate the base sand box model representative of the Kumatage field using a pre and post processing package. Multiple sensitivities such as: well depth, vertical versus horizontal wells and production rates were then conducted on this sand box model in order to develop a base case development strategy. Secondly, from the base model, the subsequent production data for GTW and gas sales was then fed into an economic evaluation of the two cases using commercial project modelling software. Upon determining the optimum case, necessary well completions required to maintain a steady production rate over the life of the field, currently defined as 20 years by the current operator, were explored. Finally, further analysis of the field was conducted to assess whether heterogeneities impact the overall recovery of the field at different gas production rates. Six further geological realisations were constructed to assess this. By examining the results from these three stages, it was found that although gas sales is more profitable in Kumatage, GTW is viable. A combined-cycle gas turbine efficiency of 50% in conjunction with an electricity price of approximately $26/MWh (NPV10 for 100% base load) is required -particularly for a gas production rate of 40 MMScf/day. The results and analysis in this paper also show that heterogeneity had a minimal impact on ultimate recovery. Heterogeneity was modelled by the inclusion of a shale barrier, whose thickness is uncertain, and by varying the porosity and permeability of the Unit A and B sands.

A discussion is also included in GTW's potential to work in conjunction with renewable technologies, such as tying back to Hornsea Project Four which is an offshore windfarm currently under the preapplication stage by Ørsted (hornseaprojects, 2019). It will be approximately 65 km from the Yorkshire coast and will be close to the Theddlethorpe and Bacton gas terminals (National Grid, 2019). By doing so, the electricity produced from Kumatage would need to be exported via a power cable to the windfarm. This study also discusses GTWs compatibility with existing renewable technologies to reduce carbon dioxide (CO2) emissions. By combining the findings of this paper, a further review of the potential of GTWs ability to unlock more marginal and stranded assets and contributing to the security of future UK energy supply. What can also be explored further from this paper is multiphase flow in the reservoir to then be able to model GTW to other offshore gas fields in the SNS.