The Story Behind The Software: PipePredictor

Looking back in history, shortly after the Big Bang and while the dinosaurs still roamed the earth ... well maybe not quite that long ago ... but it was back when ETPM was a major offshore construction company, our founder Marc Moszkowski was working for them as a project manager. Marc is something of a perfectionist and places very high demands upon himself, and even upon those around him. He likes things to be exactingly accurate (i.e. he wants me to change the first sentence of this paragraph because in the scope of time dinosaurs arrived on the earth a long time after the Big Bang and shortly before ETPM). When his mind grabs onto an idea Marc relentlessly searches for answers to questions that keep him up at night.

The question that was bothering him at that time concerned the accuracy of the pipelay software being used for the ultradeep pipeline engineering project he was managing at the time. Specifically he could not let go of the discrepancies the team had observed while laying 12 inch pipe in 5,000 feet of water. In particular he could not let go of the observation that the point of separation of the pipe from the stinger was not where it was predicted to be. In fact it was quite a ways away from where it was supposed to be. He also reasoned that the predicted angle of pipe was also incorrect. He questioned whether the tension being applied by the ship was correct. He talked to the technicians who indicated that the tension was as prescribed. He demanded they calibrate and recheck, and was surprised to learn that the correct tension was being applied. During discussion with other members of the lay team, he was shocked to learn that no one much cared or paid attention to this and to other discrepancies between the predicted parameters and the actual observations. For Marc, the quality of the software is its predictive power. In fact, the software is validated in the field every time it is used. Marc studied these issues and concluded that if the software can not accurately predict the point of separation and the angle of the pipe for a given tension, then it is likely failing to accurately predict the Touch Down Point (TDP). Further, if the software does not accurately predict the touchdown point then it is unlikely able to correctly predict the correct stress parameters imposed on the pipe by the laying process. Turns out the TDP was, in fact, not even close to the predicted location. Further if these parameters are not accurately predicted and if the stress is incorrectly calculated then one of two results are very probable. First the stress is underestimated and the project is at risk due to overstress or failure of material. Or, if the stress is overestimated then the company is wasting significant resources over-engineering and over-building the system.

If it cannot accurately describe/calculate the above named parameters, the software is useless, and even dangerous. It must be able to accurately calculate the required safety factors, the required pipe size and thickness, the stress in conditions of compression and extension and predict accurately the location of greatest stress. Turns out the maximum stress is not where most engineers in the industry think is the location of greatest stress. If its predictions are wrong, then its predictions are WRONG!

Marc continued his search for software capable of accurate predictions. He found none. He was very shocked to learn that people in the industry, were like the pipelay team, existing software was good enough. They paid little attention to the actual observed discrepancies and further did not see any reason to delve into them.

Marc developed some complex theoretical calculations to help define the problem and also enable him to better scrutinize potential software solutions. He looked at the research to find someone who had elucidated an equation that accurately described the mechanical dynamics of a large pipe thousands of pounds of tension being applied to it by a floating vessel thousands of feet above the ocean floor. He didn't find what he looked for. He made some early attempts with software that employed finite element analysis and it soon became evident that such analysis is limited in several distinct ways, the most important of which is that the finite element analysis software on the market cannot accurately define the characteristics of such a large structure extending thousands of feet down to the bottom of the sea. With time his calculation became increasingly complicated.

Marc was now dedicated to finding a solution. He soon realized that Microsoft's Excel was incapable of handling the calculations necessary to analyze the parameters and solve the problem. Excel claim to be capable of 30 digit calculations. Yet when closely observed he found that you can modify the input parameter to accept 30 digit inputs but it is of little avail since the software truncates or rounds after 15 digits when doing calculations.

He had to get creative. While this is not a venue to reveal trade secrets, suffice it to say he was able to develop an elegant solution capable of handling 664 bit binary numbers. Incredibly, such a degree of accuracy is necessary to accurately solve the problem.

Marc discussed the validation of the software and defined the following simple general concepts for the validation of his or any other pipelay software:

  • the input parameters must be correctly entered into the software
  • the software in-turn predicts outcomes or measurable operating parameters/specifications
  • the team must correctly operate the equipment according to the specifications
  • operating parameters must be observed, measured and recorded
  • if predictions and measurable outputs are the same then the software produces valid output and the team, the company, and the client can expect a top quality job that meets specifications

Specifically the software must accurately predict:

  • required tension
  • angle of lay
  • point of separation
  • location of pipe in the tower (J-lay) or in the stinger (S-lay)
  • distance to TDP
  • stress at any point along the pipeline
  • identify point and type of maximum stress
  • max weight flooded or not
  • it must predict all of the above so the enginering team can accurately predict and complete laying the pipe over pipeline crossings, valleys, crossovers, ridges, and slopes

PipePredictor accurately predicts the position, dynamics, touch down point and behavior on the barge/vessel S-lay or J-lay systems.

CASE IN POINT - Spring of 2016

Jacques Krusstall (not his real name (we have to protect the confidential information of our client) was having a problem. It seemed like a simple problem. He was tasked with attaching to and lifting a flexible pipeline and moving it a specific distance and laying it down again, in very strong currents. Seemed like a simple problem. It is not. In fact, it is anything but simple. It was thought that it would be a good idea to place a dead weight on the lower end of the pipeline and that would make it easier to accurately complete the operation. In order to place it back on the ocean floor in the correct location all the critical factors must be accurately predicted.

The other pipelay software could not accurately predict the required parameters, nor could they determine the optimal weight/size of the dead weight. What will be the shape of the pipe under the operation parameters? How much tension must the vessel exert on the pipe? What is the separation point and what is the angle of the pipe in the water? How much deadweight should be used? Jacques must know the exact location of the deadweight at all time, and especially as they are getting ready to lay it back down. He had to be sure not to exceed stress limits.

If you do not know where it is then you cannot even begin to conduct the operation. And of course how do they deal with the umbilicals and the electric cables that were used to monitor the process.

Jacques has worked in offshore construction for 40+ years, he knows most of the players, yet no one could tell him the answers to this supposedly simple problem. Yet he needed to know.

He contacted DeepGulf to see if we could help. We used PipePredictor to answer his questions. We gave him an accurate description of the operating parameters. For which he remains very grateful.