ABSTRACT The theory for stability and failure of sand arches and cylindrical holes has been applied to actual well test data. The formation tested was a poorly consolidated oil bearing sand. The well was perforated in the actual interval, but no special sand control equipment was installed. The test procedure consisted in measuring simultaneously sand and oil production as the choke size was stepwise increased. In this way the maximum sandfree production rate was established. Analysing the data, it can be concluded that the theory for arch and hole stability is capable of describing consistently the observed results.

Abstract We have studied theoretically the stresses in a poorly consolidated sand around a cylindrical well, assuming axial symmetry. Applying theories of elasticity and plasticity on this three-dimensional (3D) model, analytical solutions for all three stress components have been worked out. The existence of a plastic zone around an uncased wellbore is confirmed, and the size of the zone is determined. When allowing an incompressible fluid to flow radially into the wellbore, a stability criterion describing the failure of the sand is found to exist. This criterion relates fluid flow forces to rock strength properties. Consideration also has been given to the stress distribution around a cased hole. It is shown that a decrease in the size of the plastic zone relative to an uncased hole occurs.

Abstract When producing from an unconsolidated sand, sand arches may form behind the perforation opening. On the basis of a theoretical model, we have analyzed the stresses in the sand. The effect of flowing fluids has been studied, and criteria describing the stability and failure of the sand are given. The arching phenomenon was studied in the laboratory. The experiments qualitatively reproduced the theoretical results. To the extent that comparison was possible, the quantitative agreement between theory and experiments was fairly good.