Abstract

Destabilization of completed sandstone reservoirs reduces production rates and degrades production equipment.  A major cause of such destabilization is perforation tunnel failure, which causes sand production.

Classic mechanically-based sand control techniques are effective, but potentially unnecessary for some reservoirs.  Modeling the occurrence and severity of sand production should help identify the most economical pairing of sand control remediation methods with the desired production rate.

This paper examines an advanced technique for modeling such failures, leading to improved drilling and completion practices. In this study, 3D poro-elastoplastic finite element methods are employed to model perforation tunnel stability. Wellbore geometry, reservoir properties, draw-down rate and perforation properties such as tunnel size, spacing and orientation are addressed, with particular attention focused on the transient phenomena near perforations, including stress re-distribution and failure development for different perforations.

The results show that stability of the wellbore and perforation tunnel strongly depends upon drilling and perforation directions and perforation shot density. The relationships of the bottomhole flowing pressure, drawdown, perforation orientation, rock strength and in-situ stresses are given to provide optimal perforation for mitigating sand production.