Formation damage sometimes has a significant impact on well productivity or injectivity. Much of the work undertaken to mitigate against formation damage serves to qualify the impact of damage and for example, determine the least damaging introduced fluids. Whilst qualification is important, quantification of damage impact is a much greater prize.

Taking advantage of increased computational power and speed, Computational Fluid Dynamics (CFD) has been applied in the last five years to numerically model and quantify flow restriction in wells and the near wellbore (Byrne et al 2009). This process enables better prediction of the real impact of formation damage on well productivity. The process has been applied to many real fields and wells and in this paper we present some of the latest revelations on the impact of formation damage on well performance.

In order to illustrate the simplicity of the process a sensitivity analysis of typical formation damage restrictions has been applied. This demonstrates the impact of different formation damage quantities and depths on different well trajectories and lengths in the same reservoir. In some cases the impact of damage that could be classed as "severe" in a laboratory test has little impact on eventual well productivity. In others the damage has a profound impact on well performance. With the obvious caveat that every well is different, we propose some consistent guidelines on the impact of damage based on our numerical modelling work.

Modelling of this kind does not reduce the necessity to understand or simulate damage, instead it enables focus where formation damage has greatest impact and creates a greater awareness of the importance of damage to our industry. Through increasing use of appropriate modelling, uncertainty is reduced and better wells can be drilled and completed.

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