The use of tracer technology is becoming increasingly important to the petroleum industry and it has proven to be an efficient tool to investigate reservoir flow performance and reservoir properties that are controlling gas and water displacement processes. The tracer data have been used to reduce the uncertainty attributed to well-to-well communications, vertical and horizontal flow barriers, and residual oil saturation.
Because of lack of simple, sensitive analytical methods for gas tracers, the technical papers on gas tracers have been very limited. No cases have been found in the literature that gas tracer data have been history matched to predict the gas breakthrough time. Although there are numerous papers on water tracer, only several papers quantitatively analysis the water tracer data. So the analysis of the tracer response curve is still qualitative in nature in the petroleum industry.
This paper presents the application of gas tracer flow simulation as a means for the prediction of gas tracer breakthrough in a giant carbonate reservoir. The simulation was carried out using Eclipse. The simulation results indicate that the breakthrough times of injected solvent and gas tracers are very close. The results of our study provide valuable information for the tracer test design and field monitoring.
The interwell tracer technology applied during water/gas injection programs provide the reservoir engineer with additional information on the flood pattern in the reservoir. This information is reliable, definite and unambiguous, thus it reduces many uncertainties about the flow paths, reservoir continuity and directional features in the reservoir. Petroleum engineers can establish the reservoir continuity based on the information from different tracers produced from various wells, and reservoir barriers can be identified by non-recovery or delayed recovery of specific tracers between injectors and producers. Tracer test data also can be used to determine the residual oil saturation, and characterization of naturally fracture reservoirs.
In 1965, Brigham and Smith1 first described an semianalytic model for predicting tracer breakthrough times and peak concentration at a five-spot pattern. In this study, they assumed that the tracers moved radially from the injector to the producers through homogenous, non-communicating layers, with longitudinal dispersion in the direction of flow. The number of layers, thickness of layers, and layers' permeability were used to represent the reservoir heterogeneity.
The subsequent paper by Brigham and his co-workers2 in 1984 refined their first model and provided an analytical solution to the equations of flow in a stream tube with longitudinal dispersion. Following the publication of these two important papers, a number of tracer tests based on these models were reported.
In early 1990s Tang3–6 used another quantitative analysis method, chromatographic transform, to determine the remaining oil saturation using tracer data. Lately, Tang10 extended Brigham's model from only handling nonpartitioning tracers to handling partitioning tracers. Pope and his co-workers7–11 proposed a moment analysis in early 2000s to calculate remaining oil saturation using portioning tracer data. This moment analysis method was mainly applied to laboratory tests or Non-Aqueous Phase Liquid (NAPL) tests.