Abstract This study is focusing on sand production processes in weak sandstone formations with a uniaxial compressive strength in the range of 0 – 10 MPa, with special emphasis on the ultra-weak facies where uniaxial compression tests hardly can be conducted. The relative influence of rock mechanical properties on rock failure and sand production modes is addressed to understand sand production data from wells in a weakly consolidated basin. Results of physical model experiments of sand production from boreholes and perforation cavities as well as numerical simulations have been used along with the field data to evaluate different criteria for the onset of sand production in ultra-weak formations. It is shown how in particular the shallow and weakest strata deviates from the classical behavior of more competent formations, and a simple empirical criterion for estimation of the conditions for onset of sand production is proposed. Finally, alternatives to classical sand control strategies are discussed, which directly take into account the nature of weak sandstone.