DESIGN OF CO2-CH4 OPTIMUM COMPOSITION INJECTION AND MECHANISM USING HUFF AND PUFF METHOD AT L FIELD BACHELOR THESIS I Putu Gede Putra Arcana NIM 12215083 Submitted as partial fulfillment of the requirements for the degree of BACHELOR OF ENGINEERING in Petroleum Engineering Study Program PETROLEUM ENGINEERING STUDY PROGRAM FACULTY OF MINING AND PETROLEUM ENGINEERING INSTITUT TEKNOLOGI BANDUNG 2019 1 DESIGN OF CO2-CH4 OPTIMUM COMPOSITION INJECTION AND MECHANISM USING HUFF AND PUFF METHOD AT L FIELD I Putu Gede Putra Arcana* and Prof. Ir. Asep Kurnia Permadi, M.Sc., Ph.D.** Copyright 2019, Institut Teknologi Bandung Abstract CO 2 injection is one of the promising enhanced oil recovery (EOR) technology in the petroleum industry. This technology has been successfully applied in numerous countries by injecting CO 2 either in miscible or immiscible condition and showing significant results. CO 2 injection becomes more attractive since it does not only enhance oil recovery but also reduce the greenhouse gases which is favorable to overcome global warming. Other than CO 2, CH4 also has been the main contributor to greenhouse gases. This study aims to determine the potential of using CO 2 and CH4 as the injected fluid for enhancing oil recovery and study its oil recovery mechanisms since many studies show that CO 2-CH4 is easily injected to the reservoir and can reduce the viscosity of the oil when they dissolve into the oil. Also, the optimum mixture composition is designed in this study to achieve the highest cumulative oil production. CO 2-CH4 injection will be simulated at “L” field which has reservoir characteristic with low pressure, high temperature and light oil. Injection will be conducted using Huff and Puff method in immiscible condition because the minimum miscibility pressure is higher than fracture pressure of reservoir. Reservoir model that is generated based on “L” reservoir segment is used to forecast the production performance after CO 2-CH4 injection using CMG GEM simulator. 900 Tons of CO 2-CH4 mixture is injected for 30 days, with soaking time 14 days and production forecast is done for 180 days. The result of simulation shows that CO 2-CH4 is proven to be the potential EOR at “L” field with additional 7.30 MSTB cumulative oil production from the base case without injection which only 425.82 MSTB. Moreover, using CO 2-CH4 shows more significant result than only using CO2 with 4.42 MSTB additional cumulative oil. Other than increasing of reservoir pressure, oil swelling and oil viscosity reduction have been the most important mechanisms that improve the oil relative permeability and oil mobility which lead to higher oil recovery.