This paper reviews various applications of partitioning tracers in the petroleum industry. While non-partitioning tracers are routinely used for flow characterization and source identification, partitioning tracers have been under-utilized largely because of a lack of publicity and credibility. In theory, partitioning tracing is potentially applicable whenever a phase boundary, for instance, gas-oil, oil-water, and water-rock, exists. Partitioning between phases will slow down the partitioning tracers in a phenomenon known as chromatographic retardation, from which fluid saturations and surface properties can be deduced. properties can be deduced. Single-well tracer testing to determine residual oil saturation to waterflood S orw constitutes the most common application of partitioning tracers. More than 200 tests have been run since its first invention In 1971. In the meantime, to overcome model inadequacies, new features are continually incorporated into the simulators, making the simulators extremely difficult to run. To get around the simulation problems, a mass balance method was proposed for direct calculation of S orw from the hydrolysis rate. Based on the same principle, an internally calibrated method involving a new class of compounds which can undergo hydrogen exchange with water is being investigated. With recent advances in instrumentation and the introduction of the chromatographic transformation technique. several successful interwell tests, mostly by Esso Resources Canada Limited (ERCL), to determine residual oil saturations in watered-out and gas-saturated reservoirs have been reported. The technique involves direct comparison of the partitioning and non-partitioning tracer profiles with no need for simulation. Under ideal conditions, S or can be determined by layers. In a different approach, full-field simulation of a multi-well test has also been employed to estimate oil saturation distribution. These tests clearly demonstrate that the valuable information on S or justifies the incremental cost of including a partitioning tracer with the non-partitioning tracer in any routine tracing projects. projects. In-situ miscibility measurement by ERCL is another interesting application. Separation of partitioning tracers injected with solvent is a measure of deviation from the first contact miscibility condition FCM. Other unproven techniques including determining trapped gas saturation during a foam flood, relative permeability ratio measurement and direct logging of gamma emitting partitioning tracers through casing to determine S or partitioning tracers through casing to determine S or vertical distribution are also reviewed in the paper.
Inert non-partitioning tracers have been widely used in the petroleum industry to tag the injected fluid as well as to characterize the flow path. The tracer results provide a guideline to pattern balancing and reconfiguring provide a guideline to pattern balancing and reconfiguring for better sweep and more effective utilization of the injected fluid. Tracer response can also be indicative of in-fill drilling potential. In addition to their use in reservoir management, non-partitioning (in particular, radioactive) tracers are also employed routinely in drilling/completion and injection profile logging.