Predicting gravel pack performance is a complex and difficult task. Current practices account for expectation of performance by assigning a range of skin values that consider all the mechanisms that generate formation damage in the gravel pack. Other methods of identifying damage in the gravel pack include pressure build up analysis and the use of logging tools to investigate gravel placement. Using techniques such as NODAL® analysis, overall well performance can be validated and the level of damage within the gravel pack estimated. This practice assumes that other damaging mechanisms present at the sand face are part of the overall gravel pack damage.

This paper presents a methodology that integrates near wellbore damage, such as solid's invasion and mechanical damage during drilling, with damage caused to the gravel pack by solid particles as the well is started up for the first time. The model developed is supported by a laboratory test program of granular filter media to determine the various pore blocking mechanisms present during well start up. The results of this work indicate that impairment of the granular filter media is a function of flow rate, particle concentration and particle sizes. The final inflow model developed takes into account the volume of solids (mud cake and sand particles) that will be dragged into the gravel pack causing impairment. The result is an inflow profile from the gravel pack to the wellbore on a foot-by-foot basis that will dictate the final reservoir contribution and flow rates at the internal side of the screen.

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