The XON field is one of the five fields in the Gbaran-Ubienode to supply gas to Nigeria Liquified Natural Gas and isa field case history to illustrate the techniques and benefitsof field development optimization right from initial fieldoptimization to well delivery.The XON AB4000X reservoir is one of the largest NonAssociated Gas reservoir in SPDC and is expected toprovide more than half the gas required for GbaranCentral Processing Facility capacity of 1Bscf.Gas reserves from the 2003 Field review went down from1.6 Tcf to 1.25 Tcf post the drilling of XON 7 and forecastbased on new volumes indicate that the planned totalreservoir offtake of 500 MMScf/d (100 MMScf/d per 5 gasproducer planned for the reservoir) will only be sustainedfor 3 years instead of 5+ years. Following this, it becamenecessary to accurately estimate the Gas Initially InPlace(GIIP) , Ultimate Recovery (UR) and also providean optimum development plan for this reservoir based onthe new available data.An optimisation optimization team was put in place tobuild new static and dynamic models based on newavailable data to be used for:1. Accurately estimate in place volumes and UR2. Optimise expected reserves the ReservoirDevelopment Plan3. Support drilling campaignThe optimization optimization results have led to increasein expectation GIIP to 2.03 Tcf, represent a 22% increaseover the 2003 Field Review and a 63% over the 2005estimate.The CIIP increased to 106.0 MMstb, representinga 23% over the 2003 FR estimate.Total gas recovery hasalso increase to 1.26 Tcf which is about 20% from 2003Field Review (FR). Production rates increased from 100 to150 MMScfand compression scope of about 500 Bscf to further addvalue to the filed development.Most of the wells were delivered as top quartile wells dueto collaboration between the asset, project and wellengineering teams.
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