Since the advanced technology used in oilwell drilling is difficult and costly, the drilling must be completed in the most appropriate conditions, in the shortest time, with cost-effective and the targeted depths and purposes. This requirement has further increased the importance of drilling optimization. There are many literature studies on this subject. In this study, the data of oil and gas wells drilled in onshore Turkey were evaluated by investigating the studies on drilling optimization. It is aimed to create a new source for the literature by statistical analysis. For this purpose, the reports of 470 oil and gas wells drilled in 1963 - 2021 in onshore Turkey have been analyzed. The well locations, their average well depths, drilling operation results, drilling times and costs, log and perforation operation costs, Drill Stem Test (DST) operation costs, acidizing operation costs, workover operation costs, cement costs, drill-bit types according to commonly used International Association of Drilling Contractors (IADC) codes for drilled formations, total costs and costs per meter for the oilwells have been evaluated.