introduction
In io consulting’s (io) Powerful Thinking article “associated gas – now it’s your turn to stand up and be counted!” [1], we considered the challenges of meeting the environmental targets for associated gas in the context of oil and gas developments.
Building on this work, in this article we focus on some of the current technologies for achieving Zero Emissions Platforms and their application to a real io case study in response to such challenges.
the new aspiration: zero emissions platforms
There are very few examples of platforms which use alternative energy such as solar and wind. The renewable technology used on these platforms is typically hybrid; a combination of wind, solar panels and batteries. Shell Cutter and K17 platforms are known to be powered exclusively by renewable energy sources installed on the platform itself, which typically bring cheaper life cycle costs compared to a long power cable from a host facility. It is reported that the fabrication cost alone was around 40% of that of traditional platforms [2].
Renewable powered platforms are more suited to developments requiring low/minimal intervention on topsides facilities, e.g. low viscosity well fluids, no sand, no compression, and drill centres with a low number of wells (e.g. less than six wells). This is reflected in their minimal functionality demonstrated by the Shell Cutter and K17 platforms. Cutter is designed for a water depth of 32m and its key features include a 150te topsides occupying an area of 10.5m² including wellheads, HPUs, metering, fluids export riser, chemicals via an incoming umbilical, control system and navaids. There is no requirement for a helideck, living quarters, water treatment, fire water pump or any onboard power generation using fuel gas and/or diesel. No diesel power generation is included, hence no requirement for diesel storage or diesel supply.
Cutter’s power requirements [3] are supplied by a pair of wind turbines and a pair of solar panels. The power system comprises: two 6kW wind turbines (7m tall, 3.5m diameter blades); 68 solar photovoltaic panels with peak output of 51kW; two 6800Ah battery packs. The Cutter facility ruled out importing power from another facility and pared electrical use to the absolute minimum to enable power to be supplied from solar and wind.
This significantly reduces OPEX brought about by low maintenance, low frequency of visits and no requirements for diesel or chemical refills. Similar to Cutter and K17, further renewables powered facilities exist in the North Sea, including platforms for Nederlandse Aardolie Maatschappij’s (NAM) L13-FI-1 and Oranje-Nassau Energie’s (ONE) M07-A (shown in Figure 1).
Fig 1: From left to right, Shell Cutter, NAM L13-F-1, ONE M07-A.
io project case study
Over the last two years, io has seen an increase in interest from clients around zero emissions platforms and more broadly, the move towards energy transition. This article focusses on one of these case studies. It has demonstrated a true integration between io and its parent companies, Baker Hughes and McDermott to refine and improve certainty in its “not business as usual” NUI solution.
io’s zero emissions Normally Unmanned Installation (NUI)
This case study is a real project example. Both the project and the client cannot be named for confidentiality reasons; however, the client is a supermajor.
In the client’s asset portfolio, the installed NUIs in the area of interest were bulky and required a high degree of visitation due to the large amount of equipment and facilities on deck for maintenance and operation. Due to a heavy reliance on helicopter visits to their existing offshore platforms, the client aimed to significantly reduce visitation requirements to new NUIs. This meant a low frequency of visitation for maintenance and operations (once a year) and eliminating visits by helicopter.
At the start of the project, the client’s objectives to io was to propose a design for a NUI whilst achieving the following:
Safe & reliable facility
Low CAPEX, low OPEX and maximising value
Repeatable for future NUIs
Remotely operated
Digital platform
io’s first evaluation was to understand what the development could afford in terms of CAPEX by performing reverse economics. This determined the maximum CAPEX the development could afford in order to be economically viable. This made it clear that the wellhead platform design would need to be as minimal as possible in terms of equipment, weight and power.
In order to achieve these step changes, key elements to the design philosophy were proposed:
W2W (walk to work) vessels are used for all visits and substitute helicopters. This effectively eliminated the accommodation module; welfare facilities; helipad and supporting systems; HVAC; sewage treatment; freshwater system. The W2W vessel acts as a temporary extension to the NUI when crew visit the NUI. All supporting systems would be available on the walk to work vessel and taken away when the shift ends.
For the NUI’s material handling requirements, the W2W vessel’s crane is used or a temporary crane to substitute a permanent crane on the NUI. This reduces the power demand on the NUI, reduces maintenance requirements and diesel storage requirements. The W2W vessel crane is powered by the vessel itself and could be shared amongst multiple assets and maintained back onshore at a reduced cost.
An all-electric solution for valve actuation eliminates the requirements for a hydraulic power package or hydraulic fluid supplied by umbilical.
The design philosophy set a bottom up approach for a “no-frills” design and only equipment that was necessary to meet the functional requirements would be allowed for. From the other direction, io analysed an existing NUI asset and proceeded to strip the NUI of any equipment or systems which did not meet the functional specification of a wellhead platform. The result of taking many systems off the NUI and bringing them with the crew when required via a W2W vessel, resulted in a step change in weight and power (Figures 2 & 3) which cascaded through to CAPEX, OPEX and ultimately emissions.
Fig 2: Sankey to show the reduction in equipment weight
Fig 3: Sankey to show the reduction in electrical power demand
The dramatic change in design philosophy ultimately led to a NUI of zero emissions design. The electrical power demand was reduced to a minimum which in turn enabled a renewables solution on the NUI. This comprised a hybrid package of solar panels, wind turbine and a battery pack to smooth out fluctuations in demand and supply and to disconnect the immediate requirement for power from the ability to generate it i.e. the instantaneous power requirement may exceed what is currently being generated in which case power is drawn from the batteries. In other periods where the generated power exceeds the facility demand, the battery bank is recharged with excess electricity. While wind and solar PV individually suffer from a degree of variability, both paired together deliver a much more reliable energy stream than each would on its own.
As demonstrated in this article, renewables have been applied to offshore oil and gas platforms in the past, with many facilities already operating in the North Sea and elsewhere for over a decade. To ensure a minimum number of personnel visits, it was prudent to specify a larger renewables package for the NUI to ensure that power is always supplied. A renewables package is low cost compared to having a traditional umbilical solution providing power from a host platform with, for example, gas turbine power generation. Adding a second wind turbine and second battery cabinet was considered a low-cost mitigation measure.
Significantly reducing the number of visits to the asset and by sharing the W2W vessel amongst other assets also had a beneficial effect in terms of reducing emissions as well as operational efficiency and OPEX.
From an environmental impact perspective, there were additional advantages to this concept: a reduction in noise; low utilisation of materials of construction; smaller footprint of the platform; no footprint from laying a power cable/umbilical nor emissions from the cable installation activities.
conclusion: thinking with the “end in mind”
With initiatives such as the Zero Routine Flaring by 2030 and the movement in Energy Transition as a whole, it is expected that there will be an upward trend of near zero or zero emissions platforms. It is io’s belief that these issues must be evaluated in the early FEL stages to unlock true project value. io has project experience in this domain bringing innovative solutions and capitalising upon its technical, commercial and strategic expertise.
references
[1]insights article: associated gas – now it’s your turn to stand up and be counted!
[3] https://www.offshore-mag.com/home/article/16762969/shell-duplicates-minimal-platforms-to-cut-cost-of-ukdutch-projects