What Are The Efficiency Gains In Decommissioning Turbines?

Louise Davis

As with any rapidly developing market sector, oil & gas decommissioning inevitably comes with major potential and major risk. Here, Russell Brown discusses the current pressure on operators to adopt the most efficient end-of-asset life solutions to minimise expenditure, and how inefficient turbines should be replaced with more efficient rental solutions.

What Is The Average Lifetime Of An Offshore Oil & Gas Field?

With the average lifetime of an offshore oil and gas field in the region of 25 to 40 years, many global ageing structures are in need of decommissioning. The majority of costs are associated with the jacket, topside and subsea structure removal phases and well plug and abandon (P&A) – all of which vary depending on project and cost.

The Current State Of Decommissioning Projects

Decommissioning projects are highly complex, lengthy and expensive; the process involves many different stages and can take more than a decade to complete. With such environmental, economic and social pressures, the offshore decommissioning market is only set to drastically increase.

Decommissioning will occur on 214 fields off the UK, 106 off the Netherlands, 23 off Norway, and six off Denmark. For all four regions, there will be complete or partial removal of more than 200 platforms, plugging and abandonment of nearly 2,500 wells, and decommissioning of nearly 7,800km of pipeline. During the next five years decommissioning expenditures are set to average £1.7-2 billion/year off the UK and £400-800 million/year off Norway and to total £650-800 million off the Netherlands. Despite the industry progress and active decommissioning record, can offshore oil & gas operators guarantee that their decommissioning strategy is absolutely bulletproof?

During this period there is an emphasis for operators to adopt the most efficient end of asset life solutions in order to minimise the decommissioning expenditure, while maximising performance. As such, operators are faced with the challenge of running aged equipment, which many not be running at optimum efficiency, as well as needing to replace equipment that they know will ultimately outlive the life expectancy of the rig.


What Are The Existing Solutions For Decommissioning?

Decommissioning has been talked about for more than 10 years but have been slow to adopt due to the myriad of processes and authorities restricting operators to get approved. It can be likened to the analogy of building a house – no-one thinks about how they will knock a house down in the design stages. And, while the government is committed to help fund these projects, it understandably wants costs to reduce, so it’s no surprise that it has taken a long time to take off.

Unfortunately the downturn of 2012 has meant the adoption and knowledge share of alternative processes and equipment between peers has faltered. We are now seeing a major window of opportunity to help inform operators of how certain power solutions will help deliver innovation to minimise the larger decommissioning costs. At Aggreko, the mission is to help operators become more efficient.

What Are the Challenges Of Decommissioning Offshore?

One of the biggest challenges offshore production has faced over the years is finding a suitable, sustainable and cost-effective power source. Offshore oil & gas wells have shown to have a large amount of supply, but providing enough energy to power the rig to ensure maximum economic recovery has presented a unique challenge due to the offshore location. For rigs that have relied on gas turbines for their lifetime the decommissioning phase brings new challenges as the gas will not be available. The turbines, if they can run on diesel as well, will be inefficient and the opex associated with their maintenance will in many cases be prohibitive and crucially can balloon over time.

Turbines are a case in point in relation to aged equipment and this is where rental can be the ideal solution. Operators can hire high-performance equipment, without the need to invest capital expenditure that won’t be able to deliver a viable pay-back. With Aggreko the cost of decommissioning power can be fixed at the planning stage. This provides certainty to the operator and may even release cash to other areas of the operation.

During peak extraction periods, turbines will have played a key role in operating a lot of specialised, heavy equipment used to drill the oil. Power would have been demanded by the crane and hoisting system, large engines, pumps, electric motors, energy needs for employees on the rig to refine water, provide heating for cooking and processing waste – the list goes on. Over the years, these rigs have become their own mini cities but once this all stops the once efficient high capacity turbine solution becomes a drain on resources.

To put it into perspective, let’s take a hypothetical example of load requirements offshore. If a rig has previously been powered by two gas turbines, for example, each capable of 10MW of electrical load, those turbines were designed when the intention of the platform was to be running at its optimum. While extracting oil & gas from the ground the turbines would need to cater for lots of people and equipment, at which point they would have been very efficient. However, when you stop taking oil & gas out of the ground, the actual electrical load on the platform drops, so it might be down to say 2 or 3MW. Therefore, a 10MW gas turbine working at that level is highly inefficient because it’s using just as much fuel as in the first instance. So at what point do Aggreko generators become more efficient? If an operator required 3MW, the company would recommend three 1MW generators (running on either gas or diesel), which would burn significantly less fuel than running a 10MW turbine to provide the same amount of power.

If a turbine breaks at the end of its life, the cost of replacing and installing a new turbine in the middle of the North Sea say, would be phenomenal – estimated in the millions. This is the last thing an operator should want to do if they’re going to decommission the platform in one or two years. This is where Aggreko would advise not to repair or replace as there are alternative solutions available that offer much more flexibility. It has recently helped some of the biggest operators in their decommissioning process by supplying temporary solutions when turbines have become tired and almost redundant.

Rental equipment has a valuable part to play in the decommissioning process. It spans everything from temporary power generation to heating and dehumidification that can help preserve valuable assets and keep equipment in optimum condition to enhance their re-use or re-sale potential. Whatever the requirement, it will always be up to the supplier to maintain the equipment so the operator can focus on its core business. Not only does this mean the equipment becomes more efficient, but it also creates efficiencies in manpower.

What Is The Solution?

Temporary solutions can also provide a wealth of benefits with regards to maintenance in the decommissioning stages. Contingency plans for power are set out by strict rules and guidelines so when carrying out maintenance, temporary power solutions can provide power to conduct these works – even if turbines do still need to be running. The cost of downtime can run into the millions per week on many of these structures so that simply cannot be an option. A blackout on a platform, for example, can incur huge costs from de-manning the structures to call in helicopters and the like. This was never really a major issue until the major downturn in the oil & gas price.

The pressure is clearly on if the global decommissioning market is going to deliver the volume of projects set out at the start of this article. There needs to be more awareness of the power solutions available, which is why Aggreko values its membership of Decom North Sea in a bid to ‘enhance knowledge transfer and facilitate collaborative activities’. Whether an operator is considering piece small, piece large or one-lift topside removal, reliable rental power and temperature control is key.

Russell Brown is with Aggreko


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