ABSTRACT:

Predicting sand production accurately is a difficult task; many techniques have been investigated such as production history, mechanical property analysis using electrical log data, laboratory testing and computer modeling. In this study, the mechanisms of sand production problem in a Saudi oil reservoir producing medium oil (30 oAPI) from weak sandstone formations were investigated. Required data of this field were obtained from Saudi Aramco and by testing sandstone cylindrical core samples in the laboratories of the Department of Petroleum Engineering at King Saud University. An analytical model is elaborated based on linear-poroelastic solution of stress state around circular boreholes as well as Mohr-Coulomb failure criterion and Darcy's equations for fluid flow through porous media in vertical and horizontal wellbores. In this investigation, laboratory and field data were used to simulate sand production process (at 5000 bbl/day) in open-hole and perforated casing completions in the studied oil reservoir using the elaborated analytical model. The magnitude of loose sand grains (debris) ready to move into the wellbore from the yielded formation around the borehole (or around a perforation tunnel) was evaluated experimentally. The study was generalized to predict the on-set of yielding and the amount of generated sand debris for both vertical and horizontal wells for open-hole and perforated casing completions. It has been predicted that, at 5000 bbl/day, the formations in the reservoir are yielded around the wellbores. The amount of free sand in the yield-zone ready to move into the wellbore is within that experienced by field engineers. Thus, the studied reservoir can be produced at the desired production rate of 5000 bbl/day without harmful sand production problems if fluctuations in the production rate are avoided

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