Engineering Integration for Frontier Subsea Development
Authors: Cheldi T. , Chimisso C. , Marangoni M. 
Published: December 2007

Production of sour oil or gas from deep reservoirs extended offshore in recent years and has challenged operators to assure equipment integrity and reliability. For the development of the Aquila offshore project (850 meters as water depth) heavy importance has been placed on maintenance-free operation, safety and environmental protection. Reservoir evaluation and the engineering feasibility studies came to the conclusion that the Aquila field can be economically developed with the use of a number of advanced, integrated technologies. Due to the aggressivity of the produced oil - presence of H2S and CO2 - and the decision to exclude the use of corrosion inhibitor via capillary line, Corrosion Resistant Alloys (CRA) have been selected for tubing string. Also materials for wellhead and flowlines have been selected in order to prevent corrosion. This paper describes the technology integration in the overall Aquila project design.

Overview

With some 850m water depth, Aquila field, in front of Brindisi midway between Italy and Albania, is one of the most challenging operating scenarios in the Mediterranean Sea. The recoverable reserves have been estimated at approximately 20 million barrels of oil with an expected peak production of 17,000bpd. The development scheme is reported in Fig.1. The field is drained by horizontal wells, provided with horizontal X-mas trees. Workovers are prevented throughout the producing life of the field. Multiplex electro-hydraulic control systems will control the subsea production system. Production optimization requires gas lift reinjecting produced gas. To meet these requirements a special has been designed. Each well will be connected to the surface by individual risers systems for production, gas injection and umbilical. A floating production storage and offloading (FPSO) vessel, able to operate at 850 meter depth, will be moored baricentric to the field. Process facilities are located on the FPSO and include oil treatment, gas separation, compression and injection. The oil coming from the wells will at first be separated from the associated gas and from the reservoir water, then it will be stabilized and finally stored. From time to time the stored oil will be transferred to the refinery by shuttle tankers.

Development Philosophy

Project Management. Objective of the project is to develop the Aquila Field, that has to be considered as "marginal field", through a system able of suitable performances at costs compatible with the overall economics. To get this goal, and to give solution to the extreme technological problems. Services Companies world leader in their own domain were approached and selected. The scopes assigned are:The supply, installation and operation of a deepwater FPSO, and associated riser system; to produce oil according to the requirements at minimum cost. Convergent objectives were found and therefore technical specification and contractual agreements were jointly developed.The engineering and supply of a complete subsea system.The design, supply, installation and commissioning of an intelligent completion.

Safety Approach.

According to internal guidelines, a HSE (Health, Safety and Environment conservation) system, regarded as integral part of the whole project life cycle, has been implemented. Since the early engineering phase, safety studies, as HAZID and HAZOP, were carried out and the results were implemented into the detailed engineering. A risk assessment of the overall development system, from downhole completion up to the offloading operation, will also be performed considering equipment, operations, procedures and human factor.

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