Infill Drilling Role in Enhancing Steamflood Efficiency in Matured Steamflood Project

Abstract The operated field is a heavy oil field located in the south-central of Sultanate of Oman. The field primarily produces from Permian-age fluvial sandstones of the Gharif Formation and is developed in patterns of horizontal producers and vertical steam injectors. Steamflood has demonstrated a remarkable recovery in heavy oil reservoirs, yet numerous challenges were faced. One of which is accelerating reduction of reservoir pressure. A successful thermal recovery process requires low reservoir pressure to ensure the presence of the steam phase in the reservoir at operationally manageable temperature, facilitating enhanced heat transfer to the reservoir and reducing oil viscosity. The area under consideration is close to the flank of the structure where a number of faults cut through the reservoir that could contribute to having higher reservoir pressure. Although rock properties in the area are good, it experienced low oil recovery primarily due to the low injectivity of surrounding injectors. Hence, a horizontal infill producer (HIP) was drilled targeting unswept sand bodies. Upon commencement of HIP production, reservoir pressure in the area decreased, leading to improved injectivity in the surrounding injectors. This, in turn, increased injection rates and enhanced heat delivery to the reservoir. Drilling HIP in the area has resulted in an 8% increase in the overall area recovery factor with contributions from all producers. On the injectors level, injectivity has shown improvement ranging from three to six folds, leading to an increase in the number of active injectors supporting the area. This increase is particularly significant as some injectors were often inactive due to low injectivity historically, thereby enhancing pore volume injected (PVI) further. Consequently, underperforming producers have been successfully connected to the injectors, resulting in better sweep efficiency across area producers. As a result, oil production rate of underperforming producers doubled. Furthermore, artificial lifts are operating at better stable conditions due to improved inflow. This paper explores the implications of operating a steamflood project in a heavy oil field at high reservoir pressure. It shows the value of infill drilling in mitigating the high reservoir pressure issue and enhancing recovery in the steamflood. This approach may unlock more opportunities in areas with underperforming patterns to maximize oil recovery and flood efficiency.