A STUDY OF THE SIGNIFICANCE OF MISCIBLE WATER ALTERNATING GAS (MWAG) INJECTION TO IMPROVE OIL RECOVERY UNDER THE CONDITION OF RESERVOIR PRESSURE BELOW MINIMUM MISCIBILITY PRESSURE (MMP)

• Main Author: Arison Haratua, Yesaya
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/39861
• Institution: Institut Teknologi Bandung

Recovering oil from mature fields is becoming more vital, as finding new oil is not easy. With the uncertain oil price and high cost of exploration, the importance of maximizing the development of existing reserves is increasing. Oil fields are usually produced with the strategy of pressure depletion with production coming to an end when the reservoir pressure is too low to keep an economically viable flow rate. Many Indonesian oil fields are now in a mature stage of production with declining primary and secondary production due to pressure depletion in the reservoir. Several types of EOR applications such as miscible injection is proven to be significant in improving oil recovery. However, in Indonesia, its application is limited by a low reservoir pressure problem which is commonly found below the minimum miscibility pressure (MMP). The reservoir pressure that is below the minimum miscibility pressure causes the displacement mechanism to become immiscible and the mechanisms of achieving miscibility are required, as it is a complex matter so that a further study is required. The objective of this study is to investigate the effectiveness of Miscible Water Alternating Gas (MWAG) injection to improve oil recovery for a reservoir pressure below the MMP case using a reservoir simulation model which is conducted for the 20-year production forecast. A sensitivity analysis study is conducted by varying operational sensitivity parameters (i.e., water injection rates, gas injection rates, injection duration, and bottom-hole injection pressures), and different reservoir conditions (i.e., oil densities, reservoir permeabilities, and rock compressibilities). This study also analyzed the impact of MWAG in improving oil recovery and production performance in comparison to other EOR methods: waterflooding, C02 injection, and Immiscible Water Alternating Gas (IWAG) injection. The results prove that the MWAG injection method is favorable when the injection is applied to the reservoir as early as the production life begins and as the reservoir pressure doesn't drop too far from its minimum miscibility pressure. Also, it gives the highest result compared to other recovery methods, with 67.03% of the oil recovery factor, followed by waterflooding, C02 injection, and IWAG injection method with 58.69%, 47.15%, 41.12% of oil recovery factor respectively. The results also show that MWAG injection is effective when applied to the reservoir with heavy and medium oil, also it is applicable for a variety of reservoir permeability and rock compressibility.