Relationship Between Thick-Walled Cylinder and Unconfined Compressive Strength for Application in Sanding Prediction

ABSTRACT: A series of thick-walled cylinder (TWC) and unconfined compressive strength (UCS) tests were conducted on downhole and surface sandstones. They ranged from poorly/weakly cemented to competent high strength materials. A correlation appears to exist which relates the normalised TWC strength to UCS, thus permitting a foot-by-foot analysis of sand production potential using the model based on TWC strength. To understand the mechanisms of the correlation, studies were conducted to analyse TWC tests based on a non-linear elasto-plastic model and to examine microstructures of the tested samples. Theoretical analysis showed that the ratio of residual to peak strength is the key parameter governing the normalised TWC strength. Microscopic inspection on the polished sections revealed different failure mechanisms in the tested TWC and UCS samples.