-Managing risks in real-world software projects is of paramount importance. A significant class of such risks is related to the engineering of requirements, commonly involving the presentation and analysis of risk management arguments from both software engineers and clients involved in collaborative debates. In this work, drawing inspiration from argumentation theory in Artificial Intelligence, we introduce a number of "argumentation schemes" and associated "critical questions" to support such discussions. In doing so, we propose schemes related to risks due to excessive numbers of requirements; inadequate client representatives and poor understanding of client needs; incorrect, incomplete and conflicting requirements, and complex and non-traceable requirements. We also present a case study where the developed schemes were used to support the discussion of requirement risks in the context of a research and prototyping software project for the Brazilian Army.