Successful Field Development Strategies to Sustain Long Term Oil Productivity in Giant Sabriyah Carbonate Mauddud Reservoir: Case Study
Authors: Nelson David Jesudian , El-Din Hossam , Nair Sajan , Mohammad Hasan Ahmad , Juyal Mukul , Wenang Martine , Keot Chandan Jyoti , Osman Salih Noreldin , Mohammed Abeer Ahmed , El-Derini Khaled Mohamed 
Published: November 2017

Mauddud reservoir in Sabriyah field is a giant heterogeneous carbonate reservoir discovered in 1950s. The field is on production since 1957 with natural depletion since it has no aquifer support. Overtime, with continuous production there has been a decline in reservoir pressure which affected the field productivity. This paper presents successful field development strategies on multi-discipline approach, integrating sub-surface domains through comprehensive planning studies and high end geo-steering technologies with objective to arrest the pressure decline and sustain oil productivity from the Sabriyah Mauddud giant carbonate reservoir.

For optimum exploitation of giant Sabriyah Mauddud reservoir, KOC is currently performing high volume producer and injector horizontal wells drilling campaign. Meticulous predrill planning integrated with advance geo-steering technologies such as Multiple Bed Mapping Distance to Boundary (DTB), Azimuthal Density and Ultra High Resolution Resistivity Image helped KOC to get best results from horizontal wells, not only in short term, but more importantly long term. An effective horizontal well would minimize amount of attic oil, delay water production and hence increase ultimate reservoir recovery. To reduce overall well cost, minimize well bore instability and maximize well production, a very innovative strategy was adopted to drill medium radius 8.5" curve sections with high dog leg severity using special drilling technologies. The Mauddud reservoir varies in property and thickness in different segments of the field, therefore tailored-to-fit drainholes strategies were adopted to exploit the massive Sabriyah carbonate reservoir efficiently.

The new strategy of high dog leg medium radius ensured footage reduction by almost 50% in build section. Lower inclination through top shale sections ensured better wellbore stability and smoother drainhole. Reduction in footage meant the curve sections were drilled in less than 48 hours in a single run and resulted in huge cost savings. Another major achievement of this strategy was that landing point was positioned closer to mother bore (for sidetrack) because of reduced horizontal displacement by approx. 60%. After implementing drainhole strategies tailored to address unique challenges of particular segment of the field, horizontal producer and injector wells were successfully placed on top and bottom part respectively of Mauddud reservoir with desired exposure length, resulting in maximum reservoir contact and minimize water coning. An overall improvement of 30% in production rate and maintained water cut rate recorded on applied horizontal well case studies compared to non-horizontal wells. Consistent application on these field development strategies would be beneficial in long term by achieving increase of ultimate field recovery.

This paper provides insight on successful application of innovative field development strategies to optimize production from Sabriyah Mauddud reservoir. Field specific development plans along with innovative landing strategy and proactive geo-steering with multi boundary mapping along with high resolution resistivity imaging tools minimize geological risk and helped to achieve horizontal well and field development plan objectives. Similar approach can be adopted to sustain long term oil productivity from this type of complex carbonate reservoir.