Heavy Oil Waterflood Application of Capacitance Resistance Models

The capacitance-resistance model (CRM) is an analytical tool that uses only injection and production rate to quantify interwell connectivity and response time during a waterflood. It has been widely used in conventional waterfloods for reservoir characterization, performance evaluation and optimization. Heavy oil waterfloods introduce challenges to the application of CRM due to the high mobility ratio and its rapid variation as a function of waterflood maturity. Using conceptual reservoir models and sensitivity studies, we provide guidelines for application of CRM in heavy oil waterfloods. We illustrate our approach in two heavy oil fields under waterflood. In heavy oil waterfloods, it is observed that interwell connectivity and response time varied over time, especially right before and after water breakthrough. The magnitude of CRM parameter variation is a function of viscosity ratio between water and oil, flood maturity, and contrast of flow and storage capacity of the flow units. Case studies of heavy oil watetrflood (one mature, one immature) showed that CRM can be used for waterflood analysis, and forecasting. In the immature flood with one injector and two producers and high permeability contrast, the most extreme variation of CRM parameters was observed. In the pattern flood where injected fluid was distributed relatively evenly among producers and breakthrough had already occurred, the CRM parameters tended to be constant over time. We showed that with frequent analysis (window approach) CRM can be efficiently used in heavy oil waterfloods,