Studies on New Chemical Tracers for Determination of Residual Oil Saturation in the Inter-Well Region

摘要

This paper presents the results from the stability experiments carried out on a selected set of chemical compounds. These experiments represent one of the steps for their qualification as oil/water partitioning tracers for measurement of residual oil saturation in the inter-well region. Single-well chemical tracer tests (SWCTT) are a proven tool, frequent in the industry, to measure residual oil saturation (SO) in the near well region. SWCTT are "push-and-pull" tests where an oil/water partitioning ester will partially hydrolyze, generating a passive water tracer, often an alcohol. Oil saturation is then determined from the lag in back production experienced by the ester in relation to the passive water tracer produced during the test. Partitioning inter-well tracer tests (PITT) explore the same delay experienced by the partitioning tracer to determine SO in the swept volume between an injector and one or more producers in an oilfield. Unlike SWCTT, PITT are not frequently used in the industry, and a small number of compounds is qualified as tracer in this application. The development of new PITT tracers will help to widen the use of this technology, which has the potential to significantly contribute to enhance efficiency in oil production. To be used as oil reservoir PITT tracers, the candidate compounds must perform as required by the application under static stability and dynamic experiments. In this work, fifteen PITT tracer candidates from four families of chemicals were tested for thermal, chemical and biological stability in reservoir temperature conditions, ranging from 25 °C to 150 °C. Their interaction with three types of rock materials (sandstone, limestone and kaolinite) was also investigated in the same range of temperatures. Results suggest that six of the investigated compounds possess suitable characteristics for use as PITT tracers, while another five compounds may be used to retrieve other information from the reservoir, such as temperature or geochemical data.