Increasingly, inclusion of oil leak detection and mitigation strategies by operators is an essential requirement for achieving government approval for projects. But can such systems deliver real commercial benefits too? And how can these be realized when the currently available technologies fall short of the requirements? These questions lead us to look at similar systems for other applications, how they can be brought to bear, and, in particular, how improvements could be made in fluorescence technology for oil leak detection.

Potential commercial benefits

Effective oil leak detection systems have the potential to reduce operational risk, thereby helping to satisfy the needs of the regulators and so enabling operators to drill and produce in environmentally sensitive areas. Beyond this, though, a reliable in-place distributed oil leak detection system has the potential to help pinpoint leaks, minimizing the costs needed to address them and preventing small problems from becoming major issues.

Furthermore, it can contribute to asset integrity monitoring and, particularly in aging fields, help with optimization of maintenance and as a result minimize costs.

By borrowing technologies successfully deployed in other applications, development costs and timescales can become acceptable and system reliability can be assured.

What an oil spill detection system needs to do

First and foremost it needs to be accurate and robust. Accurate information on the location and size of leaks can help the correct resources to be sent to the right place at the right time, reducing the costs of deploying vessels and ROVs.

The maintenance burden of the system itself has to be acceptable, its lifetime commensurate with long-term offshore operation and qualified to the applicable standards.

Last, it must be cost-efficient to integrate, deploy, and operate. This means having industry standard mechanical, power, and communications interfaces; having acceptable power consumption and communications overheads; and, above all, being easy to use.

Fluorescence technology from the Cambridge Consultants’ device can detect oil drops in a water column. (Images courtesy of Cambridge Consultants)

Limitations of current technologies

A common limitation of many potential technologies, as identified in the report by Det Norske Veritas (DNV) in 2010, is false alarms. After too many false alarms, the operator loses confidence, and the system is rendered useless. This seems to be a particular problem for capacitance detectors. Hydrocarbon sniffers are triggered by natural releases of methane from the seabed, meaning it is hard to differentiate a natural leak from a pipeline leak.

Currently, there is no single sensor technology that on its own can differentiate between true leaks and false alarms 100% of the time.

Based on the DNV report, Cambridge Consultants concluded that fluorescence detection may meet these exacting requirements, given successes in other applications. Even so, fluorescence techniques are expected to be more powerful when combined with other sensing techniques.

How to address the issues

Almost 30 years ago, a novel radar system was developed to survey through Arctic ice. Since then, Cambridge Consultants has not only developed its radar capability to a world-class level but has developed sensors based on ultrasonics, fluorescence, and novel optical techniques by employing a variety of sensor technologies to solve similar problems across multiple industries.

Here are some of the key questions that Cambridge Consultants asked its researchers from the outset that are important for achieving the needs of such a system.

What needs to be measured and where? The purpose of the system has to be translated into performance requirements and identification of the confounding factors that can limit this or trigger false alarms. For example, in considering fluorescence detection as a technique, it is necessary to understand what else in the environment naturally fluoresces (e.g. plankton), what differentiates this from an oil leak (detailed characteristics of the fluorescence signals), and what the fundamental limits are to range and sensitivity that can be achieved for the fluids of interest. Also, the target environment will define the constraints on power consumption and communications bandwidth as well as the required lifetime and level of robustness.

Which sensor technology should be used? Evaluating a technology in the context of what is to be measured and where is a means for selecting promising technologies.

How the technology is implemented is also key, drawing often on our successes in other applications and different markets. For example, fluorescence detection has been implemented for a variety of medical-diagnostic applications from high-volume, low-cost, over-the-counter testers to sophisticated top-end performance diagnostic instrumentation for laboratory use. In doing so, breakthroughs in performance, cost, and reliability and the means to understand the various design tradeoffs that impact performance criteria have been achieved.

The technology achieves detection of the natural fluorescence of small amounts of crude oil using components that are inherently robust.

Is the information there, and where is it? A sensor is usually a combination of a hardware transducer, signal conditioning electronics, and data processing algorithms implemented in software. Optimal design depends on understanding whether the sensor is fundamentally capable of “seeing” what needs to be detected, whether improvements are possible, if these are to be achieved via design of the hardware or software, and how the wanted signal can be separated from unwanted noise or interference.

In the past, probabilistic techniques to answer such questions were successfully deployed. Such techniques also can be used to identify the best combination of sensors to use, how best to implement them, and how to turn uncertain data into useful information.

What does the overall system need to look like? The overall system design will depend on the area it is intended to monitor. For instance, a known trouble spot within subsea equipment that is inaccessible will require detection at a long range. Likewise, sensing leakage from a seabed fissure may require an array of sensors that communicate acoustically.

The design can be optimized to minimize duty cycle, power consumption, and communications bandwidth while considering components that meet lifetime requirements.

Next steps

DNV has recently announced a proposal for a joint industry project to develop guidelines for the application of leak detection in offshore fields.

Any effective in-place oil leak detection system almost certainly requires more than one sensing technique. Gathering real data from the field where it will be deployed is key to selecting the right sensor combination and transforming the data provided into reliable information. This can be delivered only by adopting a systems engineering approach from the outset.

Cambridge Consultants’ fluorescence detection technology offers real potential for oil leak detection. To realize it, researchers now need to work with those who stand to benefit to identify where it can usefully be deployed within a leak detection system.

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