Electrification Transformation from Offshore Power Grid to Power from Shore, a Case Study to Minimize Carbon Emissions for Two Extensive Offshore Oil Fields
Authors: Hu Yiru , Zhang Hao , Qiu Yinfeng 
Published: March 2022

With China committing to achieve carbon neutrality before 2060, the operator has set ambitious targets for minimizing carbon emissions from its oil and gas operations. Two extensive offshore oil fields – QHD32-6 and CDF 11-1 oil fields have been modified to transform its power solution from offshore generation to power from shore (PFS) to reduce carbon emission, improve offshore energy efficiency etc. The two fields comprise 25 production platforms, 2 FPSO with 21 crude oil generators and 9 gas turbine generators. The total peak power demand is about 200MW. Both QHD32-6 and CDF 11-1 oil fields have established their own offshore micro power grid by interlinking centralized offshore generation platforms via 35kV and 10kV submarine cables.

This paper first reviews the company strategic factors as well as the national regulatory drivers behind the decision to pursue whole-scale electrification of two super complex offshore oil fields. It then explores technology challenges and solutions by means of a high voltage AC PFS such as tie-in point selection, reactive compensation considerations, key economic criteria such as operation and energy costs, and asset depreciation etc. Considering the consequences of production loss due to power outage, stringent reliability requirements were adopted. A high-speed transfer combine with a 62.3km 110kV interconnecting submarine cable between QHD32-6 and CFD11-1 offshore substations is first introduced in offshore PFS installations. Detailed configuration and its power supply continuity benefit will be discussed. Finally, major cost reduction measures such as unman and digitalization design of 220kV PFS substation are summarized, with lessons learned in a successful development of extensive on-stream oil fields electrification transformation.

This electrification transformation is expected to reduce about a total 2.52 million tons of CO2 and 0.067 million tons of NOx emissions, save 2.17 billion cubic meters of fuel gas and 1.13 million tons of standard coals. In September 2021, QHD32-6 and CFD11-1 offshore oil fields have been completed the transformation and back into production. Although on account of a total 132km submarine cables and 200MW power demand, high voltage D.C. is traditionally the first choice, this paper demonstrates high voltage A.C. can be flexibly utilized for long distance large power demand by careful design.

While for many upcoming offshore projects, PFS solutions have become attractive in an effort to reduce environmental footprint, this paper presents an on-stream offshore oil fields PFS transformation, extra considerations need to be addressed. The high-speed transfer solution is first used in PFS engineering that can limit a power switching time to milliseconds, exploring a new way to significantly improve power supply continuity with limited investment. Another new information is the unmanned and intelligent design of substations to increase asset adaptability, maintain system reliability and minimize labor costs.