Traditional methods of sealing leaks, such as clamps and wraps, require direct access to the leak site so that divers or remotely operated vehicles (ROVs) can be used. Buried or

Figure 1. Platelet technology leak-repair process is shown. (All figures courtesy of Brinker Technology)
rock- dumped pipelines add to this problem in that not only is fluid egress from the leak more difficult to spot, but also the pipeline must be uncovered to apply the repair. The cost can be high due to the amount of vessel time required and loss of revenue from deferred production until a vessel is available.

Brinker Technology has developed Platelet Technology, a novel alternative to more traditional leak location and sealing methods. Adapted from the human body’s own leak sealing mechanism, it uses the fluid flow inside a pipeline to deliver discrete particles (“Platelets”) to the leak site. On reaching the site, fluid forces entrain the particles into the leak where they are held against the pipe wall, thus stemming the flow. This sealing technology also locates leaks by incorporating a traceable tracking device into each particle, generally a radioactive source. These are deployed as normal but would be detectable from injection through to entrainment. A radiation detector can be mounted on a ROV or carried in a pig to accurately locate the particle that is providing the seal. It is important to note that the seal is formed inside the pipeline at the exact location of the leak, removing any doubt as to the location of the leak.

Applications
The technique can be used in any application where there is flow in the line and a positive pressure differential acting across the pipe wall, from small bore subsea umbilicals operating at 500 bar to large overland pipelines operating at just above atmospheric pressure. Intended applications include hydrocarbon lines, gas lines, flexible flow lines and downhole repairs.

The new technology uses an advanced engineering process that includes analytical and
Figure 2. CFD analysis of platelet conveyance in a pipeline.
numerical modeling, physical testing, and material compatibility analysis to optimize the solution for each application. This allows a solution to be designed in such a way as to gain assurance that the particles will travel to and become entrained into the leak site while minimizing the number injected, making use of the turbulent flow within the pipeline to ensure that the particles are evenly distributed across the cross-section of the pipe.

Particle conveyance and distribution in the pipeline is analyzed using Computational Fluid Dynamics (CFD) as part of the design process. Depending upon the complexity of the pipeline in question, a number of numerical models will be built in a CFD software package; these will typically include a model simulating fluid flow to the leak site and another simulating the leak itself.

Simulations can be run using a number of different particle sizes and densities to ensure adequate particle entrainment at the leak site. Tuning particle density can allow for entrainment rates to be increased. Generally, particles are neutrally buoyant in the carrier fluid, and turbulence is used to ensure an even distribution. If the particles are too heavy, they will sink to the bottom of the pipeline; if they are too light, they will float to the top, resulting in an uneven distribution. Figures 3 illustrates the significant effect that a slight change in particle density can have on the cross-sectional distribution in the pipe. Crucially, this information allows the number and volume of particles injected to be reduced and still yield a successful outcome.

In some instances physical testing can be used to validate the analytical results. There are certain cases where high-pressure flow-loop testing is used to recreate the pipeline infrastructure and defect. Tests can then be run to confirm the injection process, ensure passage through any complicated sections and, most importantly, ensure that particle entrainment is achieved.

Seal integrity
In addition to ensuring that particles are conveyed to and entrained into the leak, it is also
Figure 3. Simulated distribution of neutrally buoyant platelets across a pipeline (left). While on the right, simulated distribution of positively buoyant (light) platelets across a pipeline is shown.
important to study the integrity of the Platelet seal. During the development of a solution, Finite Element Analysis (FEA) is used to simulate the behavior of a particle in various defect geometries. A fluid pressure is simulated acting over the particle, and the deformation of the particle is recorded for various pressure and defect sizes. This model allows the particle characteristics to be tuned to ensure that the required seal integrity can be achieved. Third-party materials analysis is used to determine the change in the material properties over time due to fluid exposure using an accelerated aging testing process. The tests conducted investigate the material stress-strain behavior and take account of creep effects and an assessment of chemical compatibility. This stress-strain data is then used in the FEA models.

While it may not always be possible to gain knowledge of the exact defect geometry, in many cases there is enough information to estimate the defect size and geometry using pressure and flow data to determine defect size. Likely defect types can be estimated from intelligent pigging data, and knowledge of likely leakage scenarios can be applied.

Physical testing
As an additional measure, physical testing of the seal integrity can also done using
a pressure vessel with a representative defect, as pressure vessels can typically be operated higher pressures than a flow loop. A series of pressure vessel tests to examine the integrity and longevity of the seal under real-life conditions is invaluable in providing assurance of the performance of a solution under different pressures, temperatures and fluid types.

Hazard analysis and operational planning of the offshore operation are an essential part of
Figure 4. Finite element analysis of a platelet in a defect.
the onshore preparatory work. These issues are considered at all stages of the development of a solution. Particle batch sizes are reduced by using CFD to determine the statistical probability of each particle affecting a seal. An operation on BP’s Foinaven field used around a half-liter of particles to seal a leak in a 10-in. pipeline 1,640.5 ft (500 m) subsea. As with the hazard analysis of the pipeline infrastructure, the particle injection and retrieval points must be considered on a case-by-case basis as every pipeline has different considerations and the operational requirements differ in every case.

Platelet Technology is a departure from traditional ways of sealing leaks. While it has been used very successfully as a reactive technology, the technology is equally applicable for a proactive approach where an operator has data to indicate that a leak may be imminent. As an engineered solution adapted for each leak situation, it is a rapid alternative to more traditional methods and represents a step-change in cost versus traditional methods with the potential for reduced downtime and minimized environmental impact. Easily transportable, the technology can be implemented anywhere in the world at short notice.

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