This thesis work provides a mixed integer programming model to help integrating the drilling operation and supplier selection in well drilling process of oil/gas production. The appropriate decisions on the services orders are taken based on three criteria including service duration, cost and timely deliverance. The schedule of drilling operation is based on regular working time and overtime. The research outcomes provide the optimal or rational solutions for the decisions on: supplier selection, regular working time vs. overtime planning for each activity, and the total project duration with the minimum total project cost. The two typical drilling operation project cases from a local oil/gas company are collected and conducted to validate the feasibility and effectiveness of the model. In the thesis, the conflicts and trade-offs on the business profits and project time control between the operator company and its suppliers are also discussed. To solve the problem resulted from divergent positions between the operator company and its suppliers, the sharing risk and incentive contract are suggested to be adopted by the operator companies in oil/gas production from other manufacturing research and applications. In short, this study is novel and beneficial for drilling project management as it could improve the performance of drilling operations and to integrate the activities of the suppliers.