Utilization of Gas from East Natuna Field for Improving Oil Recovery in Heavy and Light Oil Reservoir BACHELOR THESIS Renaldy Herdin Tandry 12215088 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 Utilization of Gas from East Natuna Field for Improving Oil Recovery in Heavy and Light Oil Reservoir Renaldy Herdin Tandry*, Doddy Abdassah **, and Dedy Irawan** Copyright 2019, Institut Teknologi Bandung Abstract East Natuna Gas field is the largest undeveloped gas field in South East Asia because it has high CO 2 content (71.21%). This huge CO 2 content can be used to enhance oil recovery in the oil field by utilizing Natuna Gas as an injection fluid. This study was conducted by using commercial simulator software from CMG to simulate both heavy oil reservoir (API 20˚) and light oil reservoir (API 37.4˚) with Natuna gas injection to evaluate reservoir performance. There are four scenarios evaluated in this study: production simulation with natural flow, production simulation with Natuna gas injection, production simulation for 30 years period without water injection, followed by Natuna gas injection, production simulation with water injection in 30 years period, followed by Natuna gas injection in 20 years after . The natural flow scenario gives oil recovery around 23.6 percent in light oil reservoir while gives 25.6 percent recovery in heavy oil reservoir. For the three other scenarios, light oil reservoir gives higher additional recovery than heavy oil reservoir which gives oil recovery around 65.9 – 70.5 percent in light oil reservoir and 57.6 – 66.1 percent in heavy oil reservoir. In general, Natuna gas injection gives a good performance in oil recovery for both heavy oil and light oil reservoir. In addition, the presence of waterflood does not give any significant result in total oil recovered when the reservoir was injected with Natuna Gas. The highest oil recovery for both heavy oil (66.1%) and light oil reservoir (70.5%) can be obtained by injecting Natuna gas from the beginning of the production phase. Furthermore, Natuna gas performed better in light oil reservoir compared to heavy oil reservoir. This study gives new development scenario that can utilize gas from East Natuna field for improving oil recovery in both light and heavy oil reservoir near East Natuna Field and helps to fulfill Indonesia energy needs in the future. Keywords: East Natuna, EOR, production simulation, CO 2 injection Sari Lapangan Gas East Natuna merupakan lapangan gas terbesar di Asia tenggara yang belum dikembangkan hingga saat ini karena memiliki kandungan CO 2 dalam jumlah yang besar (71.21 %). Kandungan CO2 dalam jumlah yang besar ini dapat digunakan untuk meningkatkan perolehan minyak dengan memanfaatkan gas Natuna sebagai fluida injeksi. Pada studi ini dilakukan simulasi menggunakan perangkat lunak simulator komposisional CMG dengan menginjeksikan gas Natuna ke reservoir minyak yang memiliki API 20˚ dan API 37.4˚ untuk mengetahui performa dari reservoir minyak ketika diinjeksikan dengan gas Natuna. Terdapat empat skenario yang ditinjau dalam studi ini, yaitu: simulasi produksi dengan tenaga pendorong alami, simulasi produksi dengan adanya injeksi gas Natuna, simulasi produksi selama 30 tahun tanpa adanya injeksi air, kemudian diinjeksikan gas Natuna pada 20 tahun berikutnya, dan simulasi produksi dengan injeksi air selama 30 tahun, kemudian adanya injeksi gas Natuna pada 20 tahun berikutnya. Untuk skenario produksi secara alami, tingkat perolehan minyak pada reservoir minyak ringan yaitu 23.6 persen, sedangkan untuk reservoir minyak berat tingkat perolehan minyak yaitu 25.6 persen. Untuk tiga skenario lainnya, reservoir minyak ringan memberikan peningkatan perolehan minyak yang lebih besar dibandingkan reservoir minyak berat, yaitu sekitar 65.9 – 70.5 persen pada reservoir minyak ringan dan 57.6 – 66.1 persen pada reservoir minyak berat. Secara umum, adanya injeksi gas Natuna memberikan peningkatan perolehan minyak baik di reservoir minyak berat maupun reservoir minyak ringan. Selain itu, adanya injeksi air tidak memberikan dampak yang signifikan terhadap tingkat perolehan minyak total ketika reservoir tersebut diinjeksikan dengan gas Natuna. 2 Tingkat perolehan minyak terbaik pada reservoir minyak berat (66.1%) dan pada reservoir minyak ringan (70.5%) diperoleh ketika menginjeksikan gas Natuna sejak awal reservoir minyak diproduksikan. Selain itu, gas Natuna memiliki performa yang lebih baik ketika diinjeksikan pada reservoir minyak ringan dibanding pada reservoir minyak berat. Studi ini memberikan skenario pengembangan baru yang dapat digunakan untuk memanfaatkan gas dari lapangan East Natuna untuk meningkatkan perolehan minyak pada lapangan minyak berat dan minyak ringan yang berada di sekitar lapangan East Natuna sehingga dapat memenuhi kebutuhan energi Indonesia di masa yang akan datang. Kata kunci: East Natuna, EOR, Simulasi produksi, injeksi CO 2 *) Student of Petroleum Engineering Study Program, Institut Teknologi Bandung, 2015 batch **) Thesis Adviser in Petroleum Engineering Study Program, Institut Teknologi Bandung 3 1. Introduction East Natuna Gas Field is located approximately 225 kilometers at the north of Natuna Island. The AL-1X well was the first exploration well drilled by the Italian oil company AGIP in 1973. This Large Gas Field has a total gas volume in the reservoir around 222 TSCF (Trillion Standard Cubic Feet) and proven reserves of 46 TSCF. This reserve makes the East Natuna Gas Field, the largest undeveloped Gas Field in South East Asia (Fenter, 1996). This giant gas field has a composition dominated by CO 2 (71.21 %), CH4 (26.77 %), and 2.02 % other components (Table 1). The presence of large amounts of CO 2 is the biggest challenges in the development of East Natuna Gas Field because producing gas field with high CO 2 content can cause greenhouse gas effect and lead to expensive development cost. A few studies have been conducted to develop this field, including a study by Exxon-Mobil, based on exploration license in 1980- 2006 and the study by the consortium of PT. Pertamina (Persero), Exxon-Mobil, and Thailand’s PTT EP. Back in 2017, Exxon-Mobil and PTT EP decided to left this project makes Pertamina the only contractor in this consortium (Katadata, 2017). New development scenarios are needed to develop this large gas field so it can contribute to fulfilling Indonesia’s Energy needs. Andre (2017) has proposed new development scenarios to utilize Natuna Gas for improving recovery in oil and CBM fields in Sumatera. This method can be considered because Natuna Gas contains high CO 2 content which can be used for CO 2-EOR. CO 2-EOR method was developed since Whorton and Brownscombe obtained a patent in 1952 (Stalkup, 1978). CO 2 gas injection has become an EOR method that widely used in the United States since the mid- 1980s, in Permian Basin, West Texas and Eastern New Mexico. In 2008, there were more than 100 CO 2-EOR projects and contributed to an increase in oil production of 250,000 barrels of oil per day (Perera, 2016). CO 2 can create additional oil recovery because it dissolves in oil, causing oil swelling and reduce viscosity and that help to improve sweep efficiency (Verma, 2015). Besides CO 2, Natuna gas consists of other compositions such as CH 4, H2S, N2, and other components. From the results of studies conducted by Davarpanah and Zarei in 2017, with injection rates of 1500-2000 SCFD, Injection of N 2 gas results in oil recovery of 18.51 - 23.54 %. For the same injection rate, CO 2 injection gives an oil recovery of 49.01 - 58.67%, and CH 4 injection provides an oil recovery of 46.12 - 51.89%. This implies that the injection of Natuna Gas, which is consist of N 2, CO2, and CH4, has a potential to increase oil recovery. The oil production phase is divided into three main stages, namely Primary recovery, Secondary recovery, and Tertiary recovery. Primary recovery is the phase where oil production depends on the natural pressure difference between reservoir pressure and production well pressure, also called "natural drive." Secondary recovery is used when production using primary recovery is no longer effective. Usually, primary and secondary recovery results in an efficiency of around 33 % of Initial Oil in Place (IOIP). Tertiary recovery is usually used when the reservoir approaches its end intending to increase oil recovery. This can be achieved in many ways including gas injection, chemical injection, ultrasonic stimulation, microbial injection, or thermal recovery. (Perera, 2016). This study aims to evaluate the potential of Natuna Gas being used as an injected gas to improve oil recovery in heavy oil reservoir (API 20˚) and light oil reservoir (API 37.4˚).