Abstract

The Ubit Field is the largest producing asset in the Nigerian National Petroleum Company (NNPC) – Mobil Producing Nigeria Unlimited (MPN) Joint Venture. The field has been on production for over three decades, with a YE 2007 cumulative production of 615 MBO. The predominant depletion mechanism has been gas-cap expansion, resulting in 25% decline in the original reservoir pressure of 2464 psi.

Since discovery and first development, prudent Reservoir Management practices have been used to maximize resources while managing the challenges of this field. The challenges include complex geology; drainage of a thin oil column; well performance issues related to declining reservoir pressure and the absence of pressure maintenance and artificial lift.

This paper reviews initiatives that have been adopted to optimize short to medium term production, and modeling efforts needed to underpin the longer term redevelopment programs aimed at boosting production and achieving world class recovery factor.

Optimization efforts include: GOR/voidage management, workovers, slot additions for near-term drilling, wellbore cleanouts/stimulation, contact monitoring, swabbing, well/choke optimization, gas lift, improved completion practices / optimized horizontal well placement.

These initiatives have mitigated base oil rate decline and resulted in reduced reservoir pressure decline. Other benefits include improved initial well rates at lower drawdown and higher expected per-well recoveries.

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