Subsurface Injection Monitoring in Complex Geologic Media Using Pathline, Source Cloud and Time Cloud

Abstract

Abstract Monitoring of subsurface fluid motion is critical for optimizing hydrocarbon production and CO2 sequestration. Streamlines are frequently employed to visualize fluid flow; however, they provide only an instantaneous snapshot of the velocity field and do not offer an exact representation of fluid movement under varying field conditions. In contrast, pathlines are constructed by tracking individual particles within the fluid, enabling us to trace the movement of these particles as they traverse through changing velocity fields. This paper presents the development and application of pathlines for flow visualization in complex geologic media. The flow visualization is further aided by source cloud (streak lines) and time cloud (isochrones representing moving fluid fronts). We demonstrate the power and utility of the developed tool in fractured media using Embedded Discrete Fracture Model (EDFM). Pathlines track the history of flowing particles in the reservoir. Pathlines can be spliced from streamline segments over time, tracing the trajectory of a particle under changing velocity fields. For each interval, a pathline’s end is extended with a streamline segement whose elapsed time of flight (TOF) equals the time interval. Based on the pathlines, streaklines and timelines can also be visualized. Streakline is formed by all fluid particles emitted at the same location. Timeline is the contour formed by all fluid particles emitted at the same instant and represents the fluid front movement. In 3D, these two concepts are more generally visualized in groups of points rather than lines, so we refer to them as source cloud and time cloud. The proposed injection monitoring methods - Pathline, Source Cloud and Time Cloud - are tested using a 3D field-scale model with complex geologic features to demonstrate its power and utility. The pathlines were compared with streamlines, time of flight and the water saturation distribution. Three scenarios are tested: a constant well schedule, a changing well schedule with shut-ins, and a changing well schedule with fully injection cease. Results indicate that the pathline provides more accurate swept volume, consistent with saturation distribution. The robustness of our algorithm and implementation is demonstrated with a complex Embedded Discrete Fracature Model (EDFM) with non-neighbor connections to visualize flow patterns in discrete facture network. Pathlines display the fluid flow across fractures and are subsequently used to examine the sweep efficiency and the well connectivity.