Еstimating injectivity in wells with dual injection systems to optimize reservoir pressure maintenance

Downhole systems of dual completion / injection have recently proven to be a useful tool for solving various types of tasks to increase oil recovery, monitor field development, reduce capital costs, including within the conditions of limited drilling opportunities (offshore platforms, remote fields), etc. The assemblies of dual completion / injection systems are designed for simultaneous operation separate development targets through a single borehole, which allows engineers to regulate production and injection. The up-to-date solutions for such systems ensure a more detailed monitoring of the development by equipping various types of sensors and autonomous inflow control devices. However, in case of the dual injection assembly, in particular in injection wells, the system is often equipped with one common flowmeter at a wellhead, and therefore there is no understanding of injection within a separate interval. These features impose restrictions on the processes of injection monitoring and maintaining the level of required compensation for certain targets. This paper presents an approach to assessing the injectivity of wells equipped with the dual completions technology. The algorithm is based on the analysis of actual readings from pressure sensors, calculations are performed using the equation for determining the fluid rate based on the pressure drop in the choke. The main uncertainty in the estimates lies in the correctness of the input parameter of the flow coefficient, the assessment of which is the subject of a significant part of the study. Based on the analysis, correlations were found between the rate factor and the injectivity indicators, the choke cross-sectional area, and pressure friction losses. Based on the resulting correlations, the total injectivity in the well was estimated, as well as the injectivity in the injection intervals.