Alkylpyrazines - from the “Dinner Table” to the Oilfield: A New Class of Partitioning Tracers

A partitioning inter-well tracer test (PITT) is a dynamic tool to measure the residual oil saturation (SOR) in the swept volumes of oilfields. Knowledge about SOR is an important parameter in the design of many IOR projects. Such projects are increasingly important to satisfy the global demand for hydrocarbons, as the worldwide number of mature oilfields steadily grows and very few large hydrocarbon rich basins are left unexplored. By performing a PITT before and after an IOR project is implemented, the performance of such project can also be evaluated. PITTs were first used in hydrogeology and introduced in the oil industry in the early 1970s. PITTs never became a routine tool for the characterization of oil reservoirs, however have been receiving increasing attention in recent years. The first PITTs were performed with tracer compounds successfully used in hydrogeology or selected based on the easiness of their analysis. This led often to unsuccessful tests, as the behaviour of the tracers was not well understood in the conditions encountered on the oilfield. Furthermore, environmental regulations on oil&gas production were introduced in recent years (as for example, on the Norwegian continental shelf) which restrict the chemicals possible to use as tracers. The small number of compounds thoroughly investigated and qualified for use as PITT tracer is one of the major obstacles for the dissemination of this technology. It is therefore important to develop new, functional, and environmentally acceptable partitioning tracers. Alkylpyrazines are heterocyclic aromatic compounds which are major natural constituents of flavour and aroma of many roasted and fermented foods and beverages. Their worldwide annual production is limited to a few tons primarily used by the food industry. Both scientific studies and legal guidelines consider the use of alkylpyrazines as flavour or odor agents in food products to be safe. Many alkylpyrazines exhibit physico-chemical properties which make them interesting oil/water partitioning tracer candidates. In the present work, we present the studies and laboratory testing performed on selected alkylpyrazines. Experimental and physical-chemical data was analysed to assess the possibility of using compounds from this class of chemicals as inter-well oil/water partitioning tracers. Results suggest that these alkylpyrazines, used primarily as food additives, can be transferred from “the dinner table to the oilfield” as a new class of partitioning tracers to measure SOR in the inter-well region.