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) |
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. |
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. |
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. |
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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