P523 SEDIMENTARY CYCLES ARE KEY TO IMPROVE RESERVOIR PERFORMANCE IN CARBONATES TRIASSIC LOWER MUSCHELKALK – DE WIJK GAS FIELD THE NETHERLANDS J.C.P. PIPPING 1 T CARLSON 2 H.W. FRIKKEN 1 and P.M. VALLINGA 1 Summary 1 1 Nederlandse Aardolie Maatschappij Asset Land East PO Box 28000 9400 HH Assen The Netherlands 2 Shell International Exploration and Production The De Wijk gas field was discovered in 1949 and commercial gas production started in 1955. The field is unique in the Netherlands as it contains gas in a series of reservoirs ranging from Tertiary to Carboniferous. The GIIP (Gas Initially In Place)