Design and Analysis of Electric Powertrains for Offshore Drilling Applications

Nowadays, electric actuation systems become increasingly popular in offshore drilling industry. The main advantages of this type of drives and motors are high reliability, high robustness, easy maintenance, long life and low cost. These features directly correspond to strict requirements for equipment to operate in harsh maritime environment. However, the challenge is that the applied electric motors are often too large. Therefore, improved procedures for optimal design of electrical actuation systems are needed. Typically, electric drivetrains (i.e. drive, motor, and gearbox) are often designed to work continuously under high loads, whereas, in reality, maximum load conditions acting upon them constitute only a slight share of total loads experienced during a lifecycle. Therefore, there is a need to develop design procedures for variable frequency drives (VFDs) so that their selection is adjusted to load conditions and design criteria that characterize offshore equipment. Consequently, a proper tailor-made design procedure of the whole drivetrain will lead to more efficient and less costly actuation systems. One of the analyzed aspects of the project is to analyze in details how cyclic loads affect an electric actuation system for offshore machinery. A pipe handling machine equipped with a winch is chosen as an example where the use of cyclic load handling techniques is very beneficial. A simulation model of this system is firstly created in a virtual environment. The obtained results are confronted with reference data measured on a full scale machine making it possible to validate the model. Such a reliable simulator of an electric actuation system might be successfully used in simulation based control system design. This in turn allows to investigate how to minimize energy consumption of a motor while simultaneously keeping its performance at the same level with a reduced need to conduct on-site tests. On top of that, the validated simulation model enhances analysis of the electrical system together with defining rules for optimal selection of remaining drivetrain components (motor and gearbox). The research carried out in the project so far will provide for a basis to benchmark which method (enhanced selection tool, improved control systems or combination of both) results in more compact design of an actuation system in a given application. The ongoing work contributes in two areas. Primarily, it helps to improve cyclic load handling techniques for offshore applications. Secondarily, it presents a case study on how simulation based engineering is applied to solving industrial challenges. Information regarding the Industrial-PhD project are to be found on the following website: http://home.uia.no/witoldpp/PhD_project.html

Due to the increased interest in developing new oil fields in the Arctic, it is strongly recommended that the petroleum enterprises in the years to come invest in technology which makes exploratory drilling less difficult, more cost effective and environm ent friendly. Hydraulic motors which have been typically used for offshore drilling applications since 1970s are not always suitable to operate in harsh Arctic conditions. Among their main disadvantages one can mention leakage, noise or high cost. On the other hand, some types of electric motors are characterised by improved control features, reduced energy consumption, higher reliability over time as well as lower emissions and eliminated risk of oil leakages to sea water. These drives have better impac t on the environment and offer greater flexibility in the drilling applications. The main purpose of this project is to introduce and put into wider use a new type of electric actuation system for drilling equipment used in the oil and gas offshore indus try. The project will focus on improving control strategies for electric motors to operate under varying load and environmental conditions. The developed control algorithms will be tested and verified on optimised virtual and real models of a typical offs hore drilling machine. The project will help the offshore industry to satisfy strict safety and environmental requirements associated with developing new oil fields in the Arctic.