Formal methods, like Petri nets, provide a means to analyse BPEL processes, detecting weaknesses and errors in the process model already at design-time. However, in most approaches proposed so far, the analysis is restricted to the control flow only. Analysing quality properties of BPEL processes might therefore yield false-negative results. In this paper, we are presenting an enhanced BPEL to Petri net mapping, that incorporates relevant data aspects by doing a CSSA-based analysis and applying novel Petri net patterns. The resulting formal model allows for a more precise analysis of critical properties, such as controllability and behavioural compatibility.