Abstract
Sand prevention implies an acceptable risk of sand production over the producing life of the well with no sand control mechanisms implemented. This paper reviews available methods to optimize the choice of perforation parameters (phasing, shot density and charge type) for sand prevention. Prior work has shown that sand production is preceded by failure of the perforation tunnels. In order to have successful sand prevention it is necessary to have stable perforation tunnels through rate (drawdown) changes, depletion, and water-cut. Available methods to determine the ability of perforation tunnels to produce sand free can be classified into theoretical models, experimental methods and historical techniques.
Deep penetrating charges are recommended as they produce smaller diameter perforation tunnels that are more stable than larger diameter tunnels produced by big hole charges. Optimum phasing technique relies on the maximization of distance between adjacent perforations in 3-dimensional space for a given wellbore radius and shot density. This is advantageous in avoiding inter-linking of failed zones around adjacent perforations. Data from the Magnus field in the North Sea supports the use of these two techniques in minimizing sand production. Where there are significant stress contrasts in the formation and the directions are known, oriented perforating can be used to increase the stability of perforation tunnels (especially when increasing drawdown and when depleting the reservoir).
It is shown how these three main techniques can be used to perforate for sand prevention. In addition, the paper also provides guidelines on how to avoid sand production at the time of perforation, selective perforating where there is a contrast in formation strength with depth and the use of experimental techniques to determine perforation stability due to rate (drawdown) changes, depletion and water-cut.
