Rejuvenating Field Production through Horizontal Wells in Unfavourable Mobility and Strong Aquifer Environment - A Case History

Abstract

This reference is for an abstract only. A full paper was not submitted for this conference. Abstract Maximization of recovery from multilayered, viscous and highly heterogeneous oil fields is a challenging task for operators. Heglig oil field is located in Muglad basin of Sudan wherein oil accumulation is found in multiple layers of late cretaceous deposits. The formations are heterogeneous, unconsolidated with higher viscosity and strong aquifer support. Some formations are tighter too. Field was initially developed with commingly completed vertical wells with a wider well spacing. ESP and PCP are in application for lifting the oil. Current development & production strategies and concepts implemented in the field resulted into exponential rise of water cut which reached to 90% within 10 years of production. This behavior is resulting into sharp decline of oil production and causing significant bypassed oil. This paper discusses about the midcourse correction and modification of the exploitation strategy of the field by changing the completion strategy and targeting the bypassed oil by placing the horizontal wells of optimal drainhole lengths. Accordingly, reservoir re-development plan adopted drilling of horizontal wells with suitable artificial lift techniques as one of the IOR option for maximizing well productivity in this viscous oil field. Updated static and dynamic models generated for diagnosing the bypassing of oil and saturation distribution for identifying the suitability of the locations. More than a dozen horizontal wells were drilled during rejuvenation phase which contributed remarkably in oil production, generally 2–3 folds compared to current vertical wells production. Controlled well production limiting to 1000 bopd/well by optimizing the drawdown and pump off take resulted into sustained production from the wells and controlling water cut below 40% after a year of production. The paper also illustrates how integration of different disciplines with focused efforts led to successful rejuvenation of the viscous oil field with proper well placement and sand & water control.