Understanding Reservoir Mechanisms Using Phase and Component Streamline Tracing and Visualization

Abstract

Abstract Streamline simulation has received considerable attention because of its computational efficiency and also for being visually appealing and physically intuitive. Conventionally streamlines are traced using total fluid fluxes across the grid cell faces. The visualization of total flux streamlines shows the movement of tracer and water flood front, injector-producer relationship, swept volumes for injectors and drainage volumes for producers. However, total fluxes mask many important features of reservoir flow embedded in the individual phase fluxes. These include reservoir dynamics, such as phase distribution, appearance and disappearance of phases, local drive mechanisms and reservoir miscibility conditions for CO2 or solvent flooding. In this paper we demonstrate the benefits of visualizing phase and component streamlines, which are traced using phase and component fluxes respectively. Both three-phase black oil and compositional simulation are used to visualize reservoir flow and to understand the drive mechanisms active in the reservoir. Although the phase and component streamlines are not suited for flow simulation because of their local discontinuities, these streamlines provide unique insight into the reservoir processes and recovery mechanisms. In this study, the phase and component streamline tracing is done using phase/component fluxes from commercial finite-difference black oil and compositional simulators. We demonstrate the power and utility of the phase and component streamlines using synthetic and field examples. The phase streamlines are shown to capture the dominant flowing phases in different parts of the reservoir and to help us optimize locations of infill injectors and producers. Based on the appearance and disappearance of phase streamlines, we can identify the regions of the field where different drive mechanisms such as waterflood and solution gas drives are active. The field applications involve waterflooding in a structurally complex reservoir in South America and also, a CO2 injection project in a large carbonate reservoir in Canada. We use component streamlines to track the movement of injected CO2 in the reservoir. By tracking the phase and component streamlines, we can clearly distinguish the CO2 in the gas phase and the dissolved CO2. This not only helps optimize CO2 injection but also has important implications in the effectiveness of the CO2 sequestration. Introduction Streamline Simulation is now an established reservoir engineering tool that is well-suited for geologically complex and heterogeneous reservoir systems and for convection dominated flows (Datta-Gupta and King, 2007). In many applications, streamline simulation offers particular advantages over conventional finite-difference simulation, for example for fast simulation of waterflood (Grinestaff 1999; Lolomari et al., 2000; Thiele 2001) and assisted history matching of mature fields (Emmanuel and Milliken 1998; Cheng et al. 2005). Streamline models have the added feature of flow visualization which makes it physically intuitive. Streamline models have been used for identifying swept and un-swept regions in waterflood (Alhuthali et al. 2007), establishing injector-producer relationship (Datta-Gupta and King 2007; Grinestaff et al. 1999), tracer transport (Park et al. 2006; Turan et al. 2002), water-flood allocation (Thiele 2001), predicting water breakthrough and for optimizing water injection and management of waterflood (Thiele and Batycky 2006; Alhuthali 2007), identifying reservoir compartmentalization (He et al., 2004) and statistical ranking of stochastic geo-models (Gilman et al., 2002). Using the concept of effective density, streamline simulation has also been rigorously extended for compressible flow and for compositional simulations (Cheng et al. 2007; Osako et al. 2007).