Reliability Study On Subsea Production System Considering Flow Assurance Based On Petri Net

As the key role of subsea production system to the offshore oil and gas development,many domestic companies in China are increasing the R&D of subsea production system.Both performance and reliability of subsea equipment are critical to the offshore petroleum industry characterized by high investement and high risk.No matter the reliability or performance,the target is to maximize the subsea production that is related to the concept of production assurance.It consists of installations and production flow.To the former,it is dealt with RAM analysis,while to the latter,it is handled by flow assurance.Traditionally,these two problems are tackled individually by two different professional teams,resulting in the ignorance of the dependency between them.However,it is very important for the production assurance and that's why this dissertation is here.Before starting the research,two type of reliability index are introcued.One is availability which is trantional based on the time.The other is production availability that is a little new based on performance.Then the application of them is suggested.Through discussing the roles of each participant developing the subsea engineering in terms of reliability engineering and production assurance,some advices are provided to the domestic companies.For the flow assurance issues,a rational metamodel is considered to the parameter study.And then an illustration of hydrate plug is shown.A high accuracy tool,OLGA is used to model the hydrate check and kinetics,to compute the critical time of hydrate formation and the time at which no hydrate is formed.Then the classical computer experiment design method,Latin Hypercubic Design is applied to make the samples.Using these samples,the Kriging model can be addressed,whose accuracy then is validated.It is found that the second order Gauss correlation function can deliver the better accuracy,and is appropriate to make the prediction of parameters in the flow assurance.In an effort to integrating the flow assurance and the equipment failure,the interpreted hybrid stochastic Petri net is recommended to simulate the complex dynamics of subsea production system.With respect to the difficulty of modeling the complex system with Petri net,an idea of simplifying is stated by employing a case of simple system comprising two redundant periodically tested components.Then the modular idea appears by virtue of variables supplied in the intrepred Petri nets,which procures the system modeling approach based on RBD-driven.A pile of Petri nets modules modeling subsea components and support parts are produced.In line with the RBD-driven modeling,a case made up four subsea wells is given to show the validation.The built nets are highly legible.In the basis of interpreted hybrid stochastic nets,the case integrates the hydrate plug and subsea equipment failures.Two basic indices,availability and production availability are calculated.Then some significant results are obtained.This approach will lay a solid foundation to future study of more flow assurance integrated.The subsea maintenance is of importance to ensure the production assurance.So as supplementary to the above case,the subsea maintenance activities are investigated comprehensively.Taking the subsea tree as an example,all the restrictive factors are analyzed.A simple binary model is applied to integrate all these factors to obtain the feasibility of subsea maintanence.Then the proposal of an analytic cost computation is present to quantify the affection of weather accessibility,equipment failure rate,spare parts and two contracts of intervention ship on the subsea tree's maintenance.Obviously,the presented method is quite useful to the technical support for the spare parts procurement,and tactics of intervention ship etc.