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The limitations of in-house specialists: a case of sticky oil

Sticky oil, waxy oil

At Rockflow, our team members have backgrounds as explorers, developers and operators and we’re great respecters of discipline expertise.

Out of necessity most people working in the oil industry are specialists of one kind or another (or at least, this is how they begin their career). Given the breadth of subject matter this is a prerequisite; a subsea engineer cannot be expected to undertake a reservoir sedimentological study, that’s for the geologist, but we can expect them to define a development’s subsea architecture.

So discipline expertise is vital. However, when disciplines work in silos without sufficient integration oversight, problems can arise and at times this can lead to sticky situations.

One company we know approved an offshore field development, drilled wells and put the field into production – and only a month later their export pipeline was completely plugged with wax.

 

A little context: Why is wax a problem

Many crudes have some wax tendency, but a few contain a significant, and potentially problematic, amount of wax. Once produced, crudes can deposit wax in the completion, topsides and pipelines.

The location of the deposits will depend upon many factors such as wax appearance temperature, temperature of surroundings, liquid flow rates and velocities et al. Likewise the severity of deposits will be dictated by other factors, not least of which is wax deposition volume, wax characteristics and pour point et al.

If the predicted behaviour of the wax is properly understood, then at the design stage accommodation can be made to mitigate the potential issues throughout the flow path (wells, topsides, pipelines). Such mitigations may include use of wax inhibitors and pour point depressants (injected downhole or at surface), pig design (with appropriate launch and reception facilities), process heating and appropriate field operation guidelines for wax control (pigging frequencies and chemical dosing requirements etc). If wax problems are not identified and such control measures not adequately addressed, big (and expensive) issues can result in the field operational phase.

Understanding the impact on design requirement upfront provides an informed view of the CAPEX, OPEX and safety implications of the development.

Certainly, it will take additional time in the Concept Assess and Select phase to fully evaluate and mitigate potential flow assurance issues. However, failure to do this can lead to major problems during production.

 

Millions of pounds stuck in the pipe

Now the company in question had identified the very high wax content of their crude, and conducted multiple laboratory tests to evaluate waxing behaviour in the lab, and such tests forecasted severe wax deposition.

Steps were taken, but not the right ones. The company selected a development concept that featured a Normally Unattended Installation (NUI) that exported multiphase fluids to a host processing platform. They implemented Wax suppression via inhibitor, anticipating they would need operational pigging once or twice per month. As a result, the platform safety case reflected minimal offshore attendance.

When disaster struck Rockflow were involved in key aspects of both the failure analysis and operations management to remediate the pipeline.

Many months and multiple millions of dollars later the pipeline was eventually remediated and production resumed; albeit with a radically different operations philosophy.

 

What went wrong?

The issue traced back to the concept design stage. The severity of the wax disposition, especially during colder winter months, was far greater than could be managed by inhibition and occasional routine pigging. Regular operational pigging was a design prerequisite, with a maximum pigging frequency requirement of up to three times a week.

This required a completely different design approach, as such frequent offshore attendance was not sustainable. So of course the solution blew the company’s safety case, since they had pitched it to the authorities as an unmanned operation.

Had the severity of the wax issue been understood during the design phase, the right pigging facilities could have been incorporated into the platform design. However somewhere along the line, a miscalculation had occurred during the flow assurance evaluation.

The wax deposition rate of the crude within the pipeline had been miscalculated by a few orders of magnitude – a simple spreadsheet error. As a result, they didn’t carry forward the potential wax issue into the facility design and it wasn’t flagged to the rest of the organisation.

The development was also fast tracked, since the company understandably wanted to bring on production as soon as possible. However, the company had no track record of offshore development – and they internally applied inadequate checks, balances and challenges in the design approval process.

 

A specialist problem

One part of a technical silo identified the issue and thought they dealt with it, but the rest of the company remained in the dark.

To be fair, severe wax issues aren’t a problem many people in this industry are ever faced with. So it’s difficult for them to judge the potential severity and ramifications of the subject. This is especially true when people work as specialists and often rely on others to spot and deal with issues outside their field of expertise.

In this case, the company didn’t have someone who understood the full process from reservoir to crude transfer point. Someone who could bring the requisite steer, challenge and oversight to the Concept Select activity.

 

How could it have been different:

 

1. In upstream, diagnosis needs to come before cure

In this case the oil company ideally needed to account for the severity of predicted wax deposition in the Concept Select stage, and certainly before exiting the FEED and detailed design; noting design changes later in the process incur cost and schedule delay. Once a facility is installed and commissioned, latter retrofits are typically grossly expensive.

A robust Concept Selection is the key to mitigating risk and optimising project value.

What if you’re in a hurry? Well, if you’re fast tracking it’s even more important to make sure all the right decisions are being made before you move on to the next step. You’ll know whether to install a platform, use an FPSO, go subsea, to frack or not to frack, and so on. If there’s a high chance of a downside outcome, you might tackle it in stages, or you might validly choose not to go ahead with the project.

Make those decisions early, at a point when you can impact the outcome, and they’ll mature into the front end engineering design, making a materially significant difference to the value of the project. If you wait until you’re firefighting later, you may be scrambling to preserve project value, or at best, marginally improving it.

Industry experience has repeatedly taught us that- informed early decision-making during development concept definition can positively impact the value of a project, and adequately inform the downside evaluation, whereas.
late reactive decision making during the execution or operations phase can negatively affect the value of a project. Value outcomes can differ from those promised at project sanction.

Implementing an external verification process at key points of the Concept Assess and Select process can add significant project safeguards and provide value assurance. Likewise, seeking external advice and steer in formulating the project study plan for surface and subsurface disciplines; with special focus on integration elements, can bring significant project benefit (particularly where project teams have not been extensively involved in prior Concept Assess/Select activities).

2. Concept design can’t take place in silos

In the example of flow assurance work, throughout the concept Assess and Select, if there’s any potential for hydrates, asphaltene, wax, scale or naphthenates, you need to be doubly sure you’ve accounted for it at all levels, putting flow assurance front and centre, since this will form an important part of your development feasibility. If you get any of these steps wrong, it can cause a major issue.

More broadly, this philosophy of integrated decision making needs to be front and centre of development planning processes. This is true across the entire subsurface and surface aspects of a development.

3. You need a multi-disciplinary perspective

Right now, we’re leading the Concept Assess and Select phases for another field in the Southern North Sea that has a potential wax issue.

Because we’ve seen this situation before, and because we understand its impact across the entire production lifecycle, we’re able to consider how flow assurance should guide a robust Concept Select decision. We are able to guide the subsurface and surface groups to ensure the issues are clearly understood and mitigated.

To guide projects through the design phases, you need to understand the project in its entirety. Crucially, you need to be informed by the input of specialists, but not dictated by them, asking the right questions so you can uncover the real uncertainties involved – and then select the most robust development concept.

If you don’t have individuals in your organisation who can provide this sense check, you’ll want to bring in experts who have authority in this area. If this describes you, Rockflow can provide services in field development planning from appraisal planning to Concept Select preparation for FEED and final investment decision (FID).

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