Sand Production Prediction in Oil Wellbores: A Set of Criteria for Design of Reticulated Expandable Completion Techniques Based on Large-Scale Transient Experiments

Abstract This paper provides criteria for assessing whether sanding has the possibility to occur in the wellbores that are completed by reticulated expandable completion techniques. It also presents an in-depth understanding of the mechanism under which such completion techniques control mobilization of sand grains and evaluates their long-term performance and effectiveness. A series of experiments were conducted using unconsolidated as well as weakly consolidated hollow cylinder samples to investigate the issues involved. A stiffener supported the central hole which is representative of a reticulated expandable completion technique. This was to verify whether sanding can take place when the wellbore is supported by the stiffener and if so, what influence the opening size relative to the grain size has in dictating the operational limits. Experiments were conducted on both single- and two-phase flow media. This was to explore the possible effect of a second phase in sand production in the presence of the stiffener. The experiments on weakly-consolidated sandstones showed that expandable completions were successful in preventing any shear failure around the wellbore. Under excessive drawdown/depletion, pore collapse proved to be a possible failure mechanism in the material. Nevertheless, much less sanding occurred and this improvement was attributed to grain to grain friction, enhancements of effective stresses at the wellface, and some degree of conservation of the original structure of the material. The amount of sanding at an aperture size as much as 10 times the maximum and 20 times the mean grain sizes was still very small. Experiments on unconsolidated sandstones showed that the friction between the grains mobilized by high normal stresses at grain to grain contacts played a major role in preventing sand production. The aperture size of the liner is another important factor in providing the possibility of grain mobilization. The experiments confirmed that even with a large aperture size of an order of magnitude greater than the maximum grain size, sanding did not take place under routine operational conditions in a two-phase flow medium. On the other hand, instant sanding from the sand-pack in single-phase flow experiments took place which emphasized the important role of capillarity. It was only when the maximum grain size stood at the level of aperture size of the stiffener that sanding was eliminated even under single-phase flow condition. Introduction Several expandable techniques have been implemented by the oil industry (Van Buren et al. 1999; Metcalfe and Whitelaw 1999; Hackworth et al. 2003; Echols et al. 2002; Cuthbertson et al. 2003), and their application is experiencing a rapid growth. These completion techniques are supposed to leave no gaps between the liner and the formation and, as such, avoid shear failure and disaggregation of the material around the wellbore. Although expandable completion techniques have been used in over 1000 wellbores (Gilmer and Emerson 2004), few experimental research studies have been reported on their interaction with the surrounding medium, in terms of their impact on productivity, and possible failure of the medium and its mechanism.

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