We describe results fiom the multi-partner, EU-supported SAIGUP project, the principal purpose of which is to quantify objectively the influence of geological complexity on production forecasts in progradational shallow marine reservoirs. The approch used has been to build realistic synthetic reservoirs with combinations of geological factors and to flow-simulate a 30-year production history using four different production plans on each. Formal statistical as well as more physically or geologically based, often curiosity-driven, analyses of the 20,000 sets of simulation results are used to determine the influence of geological characteristics on total oil production, recovery factor, and discounted reservoir value.