Innovative Remote Controlled Completion for Aquila Deepwater Challenge
Authors: Botto G. , Giuliani C. , Maggioni B. , Rubbo R. 
Published: December 2007

This paper describes the completion design applied for the exploitation of a deepwater marginal field in the Mediterranean Sea. In particular, it is shown how the features of a novel technology, based on remote control of downhole equipment, suit the severe project requirements and state a new paradigm in latest completion engineering.

Aquila project overview

Aquila is a marginal oil field in the southern Adriatic Sea between Italy and Albania, some 50 km North-East of the Italian city of Brindisi, in a water depth of 850m.

As of this writing, the field will be drained by two satellite subsea gas lift wells: Aquila 2, a short radius drain hole with 200m horizontal displacement drilled in 1993, tested with a 90 days Long Production Test (LPT), and Aquila 3, a medium radius drain hole with 650m horizontal displacement drilled in 1994. Each well will be tied back to a permanently moored Floating Production Storage and Offloading Vessel (FPSO) via a production riser, a gas lift riser and a multiplexed electrohydraulic control umbilical. FPSO process facilities will include oil and gas treatment, gas compression, and gas injection. A shuttle tanker will provide for oil export. Subsea operations will be performed by using the SAF (Sistema Alti Fondali), a diverless and guidelineless Agip proprietary subsea integrated system designed for 1000m water depth operations. Production of the 21 MMSTB recoverable reserves is expected to start in late 1997 and will be completed within 6 years.

Figs. 1 and 2 show the Aquila field location and development concept. For more detailed information see Ref. 1.

Completion requirements

The combination of deepwater, remote field location, and limited recoverable reserves have excluded using conventional technologies to exploit the Aquila field. Moreover, the project management required the engineers to address highly reliable solutions that could eliminate the occurrence of workovers. Following the indications of reservoir engineers, production optimization and artificial lift were the key points of the completion strategy.

Production optimization. The current status of the wells is as follows.

The 200m fairly homogeneous drain hole of Aquila 2 (Refs. 2–3) was acidized before suspension and therefore does not require any further stimulation work before starting production. On the other hand, the 650m horizontal drain hole of Aquila 3 was not acidized before suspension. Aquila 3 consists of 3 zones with different permeabilities. From heel to toe:

It was determined that the B zone should be hydraulically isolated because of the presence of a fault, which could be expected to conduct water in the long term.

Effective stimulation requires that each zone must be treated separately, due to the great difference in permeability between the remaining zones A and C.

Finally, continuous chemical treatment will be provided on Aquila 2 and Aquila 3 for asphaltene dispersion during production.

Artificial lift. A prescreening among artificial lift techniques indicated gas lift as the only viable solution.

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