An experimental investigation on the effect of rock strength and perforation size on sand production

Sand production is one of the major research subjects in petroleum industry. This is usually studied either by experimental or numerical methods. Experimental tests are usually focused on thick-walled hollow cylinder samples. In the current study, an experimental setup is introduced which is capable of performing test on large scale cylindrical samples with 15 cm in diameter and 30 cm in height. Fluid flow and confining stress can be applied to the samples. During test all the data including produced sand is recorded continuously. An innovative method is used to continuously measure the produced sand. Eight tests with similar grain size distribution are performed and the results are discussed. In order to investigate the effect of rock strength and perforation size, samples are made with 2 different hole diameters (10 and 20 mm) and 4 different rock strengths. Diagrams obtained from tests are analyzed and changes in sanding regime for different confining stress levels are discussed. The results show a direct relation between sand production and hole size while it is reversely correlated with sample strength. Produced sand at different stress levels show direct power law and exponential relation.A scenario is proposed for sanding process based on test observations. In order to combine results for different hole size and rock strengths, produced sand and stress levels are scaled according to the proposed method. This combination shows a meaningful trend for the present group of tests with similar grain size distribution.

► Different stress levels for sanding stages increase according to rock strength.
► Except sand initiation, stress levels are higher for other stages in smaller holes.
► Low strength formations are less sensitive to the hole size for sand production.
► For stronger rocks, the role of perforation size would be more important.
► Lower strength and larger hole size result in more sensitivity to change in stress.