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Home  >  Transactions OF NAMP VOL1

10. External Fluid Breakthrough Time Characterization of Horizontal Wells in a Layered Reservoir with Letter ‘F’ Architecture and Edge External Fluid Drive by E.S. Adewole Transactions of NAMP Vol. 1, (Nov., 2015), pp 77 – 82
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When external fluid (water, gas or even oil) breaks through a well, its source is seldom known with certainty. Information about the source of an external fluid, no matter the kind, is required by reservoir and completion engineers for correct advising on well geometry and completion strategy to either curb its influx or prevent it. External fluid breakthrough is preceded by fluid influx and may manifest steady state flow in the well if its compressibility is slow. Sustaining production at the prevailing rate will therefore lead to increasing volume of the "unwanted" fluid. Only production at an optimum rate would guarantee clean oil production. In terms of the required drawdown, the optimum rate and critical pressure drawdown are strongly dependent upon the breakthrough time; the largest time fluid production is possible under a constant rate without external fluid breakthrough. For largely permeable interface and layers fluids of close or different properties, simultaneous individual layer production and characterization can be achieved if regional fluid breakthrough times are known.

In this paper, external fluid breakthrough times for horizontal wells completed in each layer of a vertically-stacked layered reservoir with an architecture similar to letter ‘F’ will be derived based on reservoir pressure distribution. The derivation will consider all the possible edge external fluid influences in the architecture. The interface will be considered separately as crossflow and no-crossflow. Results show that breakthrough times are governed by reservoir layer, wellbore and reservoir or reservoir layers' and fluid properties given a constant production rate history. 

Breakthrough time expressions contain only the functions xii(x), xiii(x), vi(z) and ix(z) in the equations to be solved. They are longer for longer wells and are affected by interface permeability. For no-crossflow cases, breakthrough time is not affected directly by layers’ thickness, but is delayed where lateral lengths are greater than their thickness.