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Abstract
The rapid uptake of transient multiphase flow simulation of wells demonstrates the recognised value to the Industry of this relatively new technique. In offshore, subsea and deepwater well locations, and in long horizontal, multi-layer, multi-lateral, big-bore and complex well completions, Industry can benefit from dynamic simulation for sound engineering design, and optimisation of costs and production.
Dynamic simulation provides the possibility of building a virtual well that can be used to analyse "what if" case scenarios and predict specific results. It is an excellent tool to understand transient well behaviour and determine the optimum process to eliminate or minimise potential transient problems. It does not replace NODAL® analysis but fills a gap where NODAL® analysis techniques cannot provide solutions. Once the dynamic well model is validated it can also be used as an implicit gauge and/or a virtual DTS during production/injection operations.

This paper details some applications, and provides guidelines for the proper use of dynamic simulation in key areas including: well clean-up, well kick-off, watercut limit, flow stability, flow assurance (hydrates), gas lift requirements, large tubing ID flow, production optimisation, and well test equipment sizing.

Well Dynamic Simulation is a useful tool that can be used during FEED and at any stage of the well life cycle to "virtually" run through a complete case scenario and predict the well multi-phase flow behaviour (including trends and profiles of liquid hold-up, pressure and temperature), providing valuable information to optimise technical, operational and HSE integrity during design and operation of production systems.

Introduction
Dynamic simulation is a proven tool applied for years by facilities engineers for pipeline and slugcatcher designs. The application of multiphase flow transient simulation in wells is a new practice which requires different understanding and expertise. Multi-discipline teams or cross-discipline experience is required to properly build and integrate the well model into the total production system model.
The development of offshore, subsea, and deepwater fields and the use of more sophisticated drilling techniques and well completions require greater understanding of the transient pressures, temperatures and liquid hold-up. The high capital and operating costs, clearly merit detailed dynamic analysis of wells and associated production systems.

Currently, there are no best practice standards for the application of dynamic simulation to wells. The main objective of this paper is, therefore, to create awareness and present some guidelines to facilitate the application of this technique in order to optimise well integrity, well operations, well life cycle design and production.

Firstly, the dynamic simulation techniques are compared with traditional steady state NODAL® analysis techniques to define the areas of application.

Secondly, the main well dynamic applications (using “predictive” and “matching” approaches) are discussed and examples of relevant cases are provided. The results of which provide the confidence to use dynamic simulation in design and operations to minimise risk, uncertainty, safety hazards and environmental impact and optimise CAPEX-OPEX and production.

The dynamic simulation work covered in this paper was performed using the multiphase flow transient numerical simulator OLGA.