Guest Editorial The industry’s continued migration into deeper, hotter, and more unconventional oil and gas reservoirs carries the potential for significant financial rewards and major economic risks. Because the development of unconventional reservoirs often requires some form of stimulation—thermal stimulation for heavy oil formations and hydraulic fracturing for shale plays—well construction costs are reaching new highs. Rather than developing these wells in a trial-and-error or even blind fashion, more operators realize that the only way to maximize the value of these assets is through real-time monitoring at the reservoir level. Permanent reservoir monitoring calls for the deployment of one or more downhole sensors to monitor and record a number of reservoir properties, such as temperature, pressure, and flow rates at various locations in and around the wellbore. By monitoring these properties in real time and over time, operators can gauge the progress of reservoir development at each stage of the well’s life cycle. Full-Asset Life Cycle Benefits During fracture stimulation of shale wells, for example, a permanent monitoring solution can reliably report information on the fracture network being created, including data on both the quantity and quality of fractures being created in different zones. In steam-assisted gravity drainage (SAGD) wells, downhole temperature sensors can track the propagation of steam moving into the formation, and then the progress of heated oil moving into the producing well. Once the well is brought onto production, these same monitoring tools can accurately measure the pressures, temperatures, and flow rates of fluids at different points in the wellbore and from different producing zones. Such insight informs when the operator may need to implement some form of remediation or artificial lift in the well to boost dwindling production rates. Once artificial lift has begun, the real-time reservoir data can help optimize the pumping rates of various lift technologies to maintain production at desired rates. The benefits of permanent reservoir monitoring extend past a single well to encompass production optimization at a field level. For example, by installing permanent sensors in producing, injection, and monitor wells as part of an enhanced oil recovery (EOR) campaign, the operator can feed these data into simulation models to track production across the reservoir. Such information can then be used to aid development decisions—an expansion of EOR or the drilling of additional wells—to boost the long-term production of an entire field. Weighing Monitoring Options The past 2 decades have brought an impressive pace of development for different permanent downhole monitoring options. For operators, the choice of a system is a function of several interrelated factors.