Abstract

The use of tracer technology is becoming increasingly important to the petroleum industry. In addition, tracer technology has proven to be an efficient tool to investigate reservoir flow performance and reservoir properties that control gas and water displacement processes. Tracer data has been used to reduce uncertainty attributed to well-to-well communications, vertical and horizontal flow, and residual oil saturation.

Unfortunately, at present, analysis of the tracer response is still largely qualitative in nature, and most information given by the monitoring of the tracers is not quantitative. Among the numerous papers found on tracer technology, several include history matching of water-tracer test results. Only one paper includes history matching of gas tracer test results.

This paper also describes the development of tracer modeling technology in the petroleum industry, from the first quantitative tracer study in the 1980s to the latest quantitative tracer study in the 2000s. The results of our study indicate that only a small number of interwell tracer studies employed numerical modeling methods. In addition, tracer analysis methods in the petroleum industry are not well studied. However, they are better studied in the hydrology industry. Tracer modeling methods deserve to be paid more attention, so that petroleum engineers can take better advantage of results from costly tracer tests.

Introduction

Although tracer tests1 were developed for tracking the movement of groundwater in the early 1900s, they were neglected by the petroleum industry until mid 1950s. At this time, petroleum engineers2,3 started to conduct tracer tests for determination of flow of fluids in waterflooded reservoirs.

In the petroleum industry, solvent is sometimes injected into oil or gas bearing formations for the purpose of producing more hydrocarbons. Tracers can be added to the injected solvent to determine where the injected solvents go. The subsurface flow in the reservoir is anisotropic, and the reservoirs are usually layered with significant heterogeneity. As a result, solvent movement in the reservoir is difficult to predict, especially in reservoirs containing multiple injector sand producers. However, the flow paths can be identified by tagging solvent at each injection well with a different tracer and monitoring the tracers appearing at each producing well. Therefore, multiple tracers are often used for interwell tracer tests in the petroleum industry.

Interwell tracers can provide information on flood patterns within the reservoir. This information is reliable, definitive and unambiguous, thus it helps reduce uncertainties about flow paths, reservoir continuity and directional features in the reservoir. Therefore, petroleum engineers can obtain information on reservoir continuity from the amount of each tracer produced from each well. Reservoir barriers can be identified by non-recovery or delayed recovery of specific tracers. At the same time, tracer test data can help determine residual oil saturation. Tracer test results also provide information on fracture characteristics in a naturally fractured reservoir.

The scope of this review is interwell tracer tests and studies in the petroleum industry. Consequently, all experimental works and theoretical studies on tracer flow are not included in this study

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