This thesis study the possibility of riser slugging control in oshore oil productionusing a subsea choke valve. A 5-state simplied model of a well-pipelinerisersystem is introduced and tted to a reference model in the ow simulatorOLGA. The models have two inputs, a subsea valve at the wellhead and a topsidevalve at the top of the riser. The eect the valves have on the behavior ofthe simplied model are tted to simulation data from the OLGA-model usingbifurcation diagrams.An input-output controllability analysis of the simplied model show thatanti-slug control using a subsea valve at the wellhead is more dicult than theconventional solution, which is to use the topside choke valve. This is conrmedby simulations on the simplied model using Hinfinity-controllers.Stabilizing control of the OLGA-model using the subsea valve was unsuccessful,despite testing dierent measurement combinations and control structures.A more promising solution for controlling riser slugging using a subsea valve istested in OLGA, where a subsea valve located near the base of the riser can keepthe system stable at riser slugging conditions. This is also seen in an experimenton a small scale ow lab.

Subsea petroleum extraction systems may be large and complex, and many decisions affect the production. Maintaining high production levels is not a trivial task. As decisions are made based on available information and experience, better decisions come with better information. Decision support tools may provide essential information to achieve better production levels.In this master thesis, different methods are proposed as decision support tools. The aim is to increase the production from a part of a subsea production system, consisting of a manifold with seven producing wells and two flowlines, given certain system constraints. The methods are based on well models and numerical optimization, and both static and dynamic optimization is considered. The well models are non-linear, and binary decisions are also present. The problems that arise are complex MINLP problems, and are solved by combining ’brute force’, ’Branch & Bound’, and a nonlinear solver. The solution of the problems is implemented in MATLAB, and tested on predefined test scenarios, with no, little or extensive dynamics present. The performance is assessed by simulations, and by calculating the resulting average production.It was found that static optimization to decide the well settings, such as valve openings and flowline routing, has a great potential to increase the oil production from the system. The results when applying a dynamic approach to the system were not conclusive, but the methods proposed showed no indications of any major performance increase, relative to applying only static optimization.

Det övergripande syftet med forskningsstudien är att få en ökad förståelse för hur rekreation kan komma till uttryck i fritidshemmet. Intentionen är att ta reda på hur både elever och lärare uppfattar rekreation i fritidshem. Studien bygger på semistrukturerade intervjuer där syftet är att få en ökad förståelse för hur lärare i fritidshem upplever sitt arbete med rekreation.  Då vårt syfte även är att ta reda på elevers upplevelse av rekreation i fritidshemmet har vi använt ett designat barnsamtal. Studien genomförs med sex lärare samt sexton elever på två olika fritidshem. Resultatet av studien visar att lärare i fritidshem upplever en viss osäkerhet kring rekreationsbegreppets innebörd samtidigt som de främst kopplar rekreation till lugna och stillsamma aktiviteter.  Studien visar även att lärarna anser att elever har större möjlighet att uppleva rekreation under sin fria tid i fritidshemmet vilket är samstämmigt med vad analysen av studiens genomförda barnsamtal visar. En central del i elevers upplevelse av rekreation i fritidshem grundar sig i deras känsla av att ha roligt vilket leder till en samlad bedömning av att elevers upplevelse av rekreation till stor del kan likställas med att ägna sig åt lustfyllda aktiviteter.