Glider Development
Authors: Sinclair R.V. , Pettibon J. 
Published: October 2008

Shell Exploration & Production (Shell) discovered the Glider field in 1996 in Green Canyon 248, Gulf of Mexico. Initially the field was thought to contain sufficient volume to warrant development via a Tension Leg Platform, however, a later appraisal well drilled in 1997 was disappointing. Since that time the venture team has worked two fronts; increasing confidence in proven and potential volumes and reducing system costs to make the field economically attractive as a subsea tieback. This paper will discuss the work done to reduce system costs.

Introduction

Like many small fields Glider was challenged to remove cost from the development plan to meet investment criteria and attract funding in a global business environment.

The conventional Shell approach for a deepwater subsea oil tieback, the preferred option for Glider, has been to provide a robust system built from standard components with minimal flow assurance risk. For example the system would include features like dual flowlines with the ability to hot oil and remediate hydrates by dual-sided depressurisation from the host platform.

The selection process for the Glider subsea system aimed to capture the benefits demonstrated by standardization of system components in previous projects whilst challenging other functional requirements to remove cost from the development. The system has been selected using a risk based approach, balancing the benefits of a system with lower initial capex against the potentially higher through life operating costs eg. cost associated with remediating / recovering from a flow assurance event such as a hydrate plug in the flowline.

The key flow assurance issues for Glider are hydrate, asphaltene, and wax. For each of these, the impact to longterm operation was assessed for a number of different system configurations including dual flowline, single flowline and single flowline combined with a service line.

The Glider project execution phase was also challenged to reduce cycle time, the time from project sanction to first production. A target cycle time of 4 months is considered achievable by leveraging standard systems and components and selective pre-sanction commitment to long lead items.

The successful implementation of the Glider systems will extend the range of standard solutions available for Shell's portfolio of future subsea field developments and reduce the time required for system design.

In September 2003 Shell (75%) and Newfield Exploration (25%) sanctioned the Glider development as a subsea tieback to the Shell operated Brutus TLP in Green Canyon 158. The development is currently in the execution phase with first production scheduled for mid 2004.

System Selection

Key data for system selection was:Water depth 3500ftHost approximately 6 miles to NWInitial production rate 30mbd, GOR +/- 900 scf/bblTwo wells in phase one - one new well and completion of an existing appraisal well.Well offset spacing at mudline 3900ft.Provision for re-completion and/or connection of an additional well in phase two.Natural aquifer drive in deeper zones; possible depletion drive in shallower zones