The Casablanca Subsea Completion System Design, Installation, and Operation
Authors: Strader John B. 
Published: October 2008

A comprehensive description and evaluation is made of the 440 ft water depth Casablanca driverless subsea completion system offshore Spain with respect to design, installation and operation.

The development of the system from initial design to field operating experience is described in detail. Installation vessel requirements and modifications are described as well as the actual installation sequence.

The selection of the completion system is discussed with respect to well requirements, environmental conditions and operational flexibility. This system is unique in that it was designed for both early production to a floating production facility and for future long term production to a fixed platform.

Results show how a successful subsea completion project is conceived and implemented. It is shown how various production considerations (i.e .high temperature oil and high flow rates) are accommodated by design. Operational flexibility is addressed as a major factor in maintaining on-line availability.

Introduction

The Casablanca subsea completion system was designed to control the flow of crude oil from a deepwater subsea well to a remote surface production facility. Major system components include Christmas tree and flow line equipment, installation and work over tools, installation and work over controls, and production controls. The overall system was designed to provide a safe, reliable and economic method for producing oil in deep water from subsea wells as are found in the Casablanca Field, offshore Northeast Spain.

This paper focuses on the various aspects of designing, testing, installing and operating this subsea production system, with particular emphasis on the Casablanca 6 well installed during the winter of 1979-1980. The key sections of this paper discuss the following areas:–Field Criteria–Design Philosophy–Completion System Configuration–Installation Work over Controls–Production Controls–Onshore Testing–Vessel Preparation–Transfer Offshore–Completion System Installation–Production Startup–Production Operation–Conclusion and Comments

Field Criteria

The Casablanca Field is located approximately 60 km. offshore Tarragona, Spain in water depths over 440 feet. Environmental conditions range from mild in the summer months to moderately severe in the winter.

The field was discovered in 1975 with the drilling of the Casablanca 1 well. The well was put on an extended production test using a drilling BOP and riser. Test results indicated that the Casablanca structure was capable of high production rates.

This production test also showed that flowing wellhead temperatures of up to 300' F would be encountered at flow rates over 10,000 BBL/Day. No significant solids would be produced. The oil was of a light gravity, with small amounts of H2S and C02 Water cut was expected to be negligible for most of the life of the field.

Additional delineation wells were drilled to confirm reserves. A detailed development study was performed, confirming the viability of a number of development schemes. At that time subsea completions were cons indeed as a means of either developing the entire field or as satellite installations for early production and to augment production to a fixed platform at a later date.