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. Injected fluid composition of 90% CO 2 and 10% CH4 demonstrates the most encouraging EOR mechanism which results in the highest cumulative production. Therefore, the most optimum injected fluid composition which is potential to enhance oil recovery is 90% CO 2 combined with 10% CH4 with the following EOR mechanisms: reservoir pressure incremental, oil swelling, and viscosity reduction. Keywords: immiscible huff and puff, CO 2-CH4 injection, optimum composition Sari Injeksi CO 2 merupakan salah satu metode yang menjanjikan sebagai teknologi peningkatan perolehan minyak (EOR). Teknologi ini sudah sukses diaplikasikan di banyak negara dengan menginjeksikan CO 2 secara tercampur atau tak tercampur dan menunjukkan hasil yang signifikan. CO 2 menjadi lebih menarik karena selain meningkatkan perolehan minyak, juga dapat mengurangi akumulasi CO 2 yang juga dapat mengatasi pemanasan global. Selain CO 2, CH4 juga menjadi penyumbang utama untuk efek gas rumah kaca. Studi ini bertujuan untuk mengetahui potensi menggunakan CO 2 dan CH4 sebagai fluida yang diinjeksikan untuk meningkatkan perolehan minyak dan mempelajari mekansimenya karena banyak studi yang menyebutkan bahwa CO 2-CH4 mudah untuk diinjeksikan ke reservoir dan dapat mengurangi viskositas minyak ketika CO 2-CH4 larut dalam minyak. Komposisi optimum dari CO 2-CH4 juga akan didesain untuk mendapatkan produksi kumulatif minyak tertinggi. 2 Injeksi CO2-CH4 akan disimulasikan pada lapangan L yang memiliki karakteristik reservoir tekanan rendah, temperatur tinggi, dan kandungan minyak ringan. Injeksi ini akan dilakukan dengan metode Huff and Puff dalam kondisi tidak tercampur karena tekanan tercampur minimum memiliki nilai lebih tinggi dari tekanan rekah reservoir. Model reservoir dibuat berdasarkan segmen reservoir dari lapangan L yang nantinya akan digunakan untuk memprediksi performa produksi setelah dilakukan injeksi CO 2-CH4 menggunakan simulator CMG GEM. Sebanyak 900 Ton campuran CO 2-CH4 akan diinjeksikan selama 30 hari dengan waktu perendaman selama 14 hari dan prediksi performa produksi selama 180 hari. Hasil simulasi menunjukkan bahwa injeksi CO 2-CH4 terbukti potensial sebagai metode peningkatan perolehan minyak pada lapangan L dengan peningkatan produksi minyak kumulatif sebesar 7.30 MSTB dari kasus tanpa injeksi yang hanya menghasilkan kumulatif produksi sebesar 425.82 MSTB. Bahkan, menggunakan CO 2-CH4 sebagai fluida yang diinjeksikan menghasilkan hasil yang lebih signifikan jika dibandingkan hanya dengan menggunakan CO 2 yang hanya menghasilkan peningkatan produksi kumulatif sebesar 4.42 MSTB. Selain meningkatkan tekanan reservoir sebesar 173 psi, mengembangnya minyak dan berkurangnya viskositas minyak merupakan mekanisme terpenting untuk meningkatkan permeabilitas relative minyak dan mobilitas minyak yang menyebabkan peningkatan perolehan minyak. Injeksi fluida dengan 90% CO 2 dan 10% CH4 menunjukkan mekanisme peningkatan perolehan minyak terbaik dan menghasilkan produksi kumulatif minyak tertinggi. Maka komposisi optimum fluida yang diinjeksikan adalah 90% CO 2 dengan 10%CH4 yang dapat meningkatkan perolehan minyak dengan mekanisme peningkatan tekanan reservoir, mengembangnya minyak, dan pengurangan viskositas minyak. Kata kunci: injeksi tak tercampur Huff and Puff, injeksi CO 2-CH4, komposisi optimum *) Student of Petroleum Engineering Study Program, Institut Teknologi Bandung, 2015 batch **) Thesis Adviser in Petroleum Engineering Study Program, Institut Teknologi Bandung 1. Introduction 1.1. Background Enhanced Oil Recovery (EOR) is one of the most advanced technology in the petroleum industry to increase the total amount of oil recovered by following techniques including gas injection, chemical injection, microbial injection, or thermal recovery (Lake, 2015). CO 2 flooding has been the most widely used as EOR technology for medium and light oil production in sandstone and carbonate reservoirs during the past few years (Godec et al., 2011). CO 2 EOR also has been known as the second largest EOR technology in the world, after the thermal recovery (Kulkarni,2003). The study of CO 2 EOR originally emerged in the 1930s and showed a significant improvement in the 1970s. The first large-scale and commercial CO 2 EOR project started to operate in 1972 at the SACROC field in West Texas and many other projects are continuing nowadays. Based on 2010 EOR survey by the Oil and Gas Journal, there are a total of 129 CO 2 EOR projects globally, which 120 of them are located in the U.S. and Canada. According to the U.S Department of Energy, in the U.S. only, CO 2 injection has accounted for the recovery of about 1.5 billion barrels of oil. During CO 2 EOR process, the oil will be dissolved with CO 2 and lead to the increase of oil mobility, and therefore, the injection of CO 2 into oil reservoirs will give significant ability to enhance oil production. CO 2 can be injected into a depleted oil reservoir through two mechanisms, miscible and immiscible injection. Miscible CO 2 injection is done under the condition in which the gas and oil phases mix and creates a homogeneous phase without the existence of an interface. Miscible CO 2 injection only possible above minimum miscibility pressure (MMP), which depends on temperature and properties of reservoir fluid (Perera et al., 2016). The reservoir that insufficient to reach minimum miscibility pressure will preferably be carried under CO 2 immiscible injection. Despite its lower displacement efficiency, however, immiscible CO 2 flooding is increasingly being considered for enhanced oil recovery, especially from medium and heavy oil reservoirs. (Saner and Paton, 1986) It was found that huff and puff CO 2 injection have wider application in the light oil reservoir (Thomas and Monger, 1990).