Complex fault-block oil reservoirs, marked by advanced fault systems, limited sandbody areas, and diminished formation energy, frequently encounter difficulties in establishing efficient injection and production systems within the sandbodies, resulting in a precipitous decline in oil output. This study proposes a method to calculate the water flooding control degree using the probability distribution curves of sandbody parameters, based on the predicted distribution characteristics of these parameters from sedimentary rules, aiming to optimize well patterns and enhance the water flooding control degree. Firstly, the shapes of sandbodies are categorized into three types, and engineers provide the probability distribution curves for each parameter through preliminary geological research. Secondly, parameter values are extracted randomly from these distribution curves to construct sandbodies, and simulations are performed to evaluate the water flooding control volume of different well patterns under these sandbody conditions. When the number of extractions is sufficiently large, the constructed sandbody distribution aligns with sedimentary patterns. Finally, water flooding control degrees of different well patterns are calculated to select optimal deployment schemes. By investigating the variation patterns of water flooding control for three types of well patterns (inverted nine-spot, inverted seven-spot, and rectangular five-spot) under different sandbody shapes, the optimal and worst well row directions for each pattern are determined. Applied in H block of the Tanan Oilfield, this method demonstrates favorable outcomes. It avoids errors associated with geological modeling and is of great significance for the timely energy replenishment in complex fault-block reservoirs at an early stage.