Development and Field Testing of a New Diverter Sub Model for Gravel Pack Operations

Abstract

A significant recent advancement in sand control technology is the use of diverter subs in conjunction with shunt tube gravel packing, further increasing the application window of this popular technique. This follows several reported cases where excessive amounts of slurry were lost to the formation after exceeding the fracture pressure and, despite the use of shunts, the screen annulus was not completely packed. Diverter subs minimize this risk by allowing fluid to bypass portions of the wash-pipe, which helps to reduce bottom hole pressure and maintain it below the fracture pressure. However, this effect is heavily dependent on the number and placement of diverter subs, so effective modelling becomes critical as improper design may still fracture the formation and result in an incomplete pack. The introduction of diverter subs results in fluid being distributed in multiple directions at various points along the wellbore, making the flow path progressively harder to model as the number of subs increases. Consequently, no models existed that could accurately design or evaluate shunted gravel pack treatments with diverter subs. This paper discusses the development and validation of the industry’s first simulator which incorporates diverter subs with a commercially available gravel pack model to accurately design their optimal number and placement. This was validated with a case history using both shunts and diverter subs, confirming the model can accurately design and evaluate these complex treatments. The paper further extends this work to demonstrate how the model can be used to optimize future designs, expanding the application window of these treatments into tight pore-frac margin wells by reducing the risk of incomplete packing.