In practice, reservoir water flooding is widely used to increase oil recovery.
Establishing reliable control over flood water relocation and oil displacement makes it possible to decrease the volume of the supplied water and to provide efficient work of the oilfields. At the present time, such a control is exercised on the basis of indicator (tracer) researches which allow:
- to determine the direction, speed of motion, and the spread of injected water in the productive volume of the well;
- to determine pumping wells, i.e. the sources of water encroachment of production wells;
- to control the efficiency of the applied methods increasing reservoir recovery.
Organic fluorescent dyes (fluorescein, eosin, etc.) as well as radioactive isotopes (tritium, etc.) added to the injected water are used as tracers, with the further analysis of the content of tracers in the testing samples taken from the producing wells.
Tracing substance in specific conditions of a reservoir should not:
- be sorbed by geological material
- contain the analogues in stratal liquids
At the same time, tracing substances should
- be well dissolved in the observed liquids
- preserve its physical-chemical characteristics during the exercised control
- be rather accurately fixed in a wide range of concentrations
- follow its hydrodynamic carrier not disturbing the natural flood
- be cheap, easy-to-operate, and available for wide application
- be environmentally friendly
- be safe for the maintenance staff
Organic dyes and radioactive isotopes do not meet all of the requirements mentioned above.
Stable nitroxyl radicals proposed as tracers are chemical substances with extremely low threshold in the determination of concentration (up to 10-12 mole). Stable nitroxyl radicals and their precursors are used in biological, medical and other researches to control the migration of labeled compounds and the course of intracellular processes.
The given technology is based on the placement of the precursors of stable nitroxyl radicals into the injected liquid with their further transformation to radicals when preparing the selected sample for the analysis by the method of electron paramagnetic resonance (EPR). EPR method can be used to determine not only the concentration, but also the structure of the radical, which make possible simultaneous identification of different tracers placed into many pumping wells of the deposit under investigation.
There exist no natural analogs of the nitroxyl radicals obtained by the synthesis. The research has shown low adsorbability of its precursors in strata with preservation of their physical-chemical properties. Stable nitroxyl radicals and their precursors are environmentally friendly substances safe for the maintenance staff.
Patents
The developed methods of synthesis of the chemical substances obtained from the available cheap raw materials were protected by the patents of the Russian Federation and can be applied in the production of a wide range of tracers stable in various media.
Practical realization
Production lots of stable nitroxyl radicals are produced on the Pilot Plant of the Novosibirsk Institute of Organic Chemistry of SB RAS.
A series of industrial tests of the tracers proposed has been conducted in the oil fields of Bashkortostan.
Commercial offers
Delivery of pilot lots. Participation in the development of tracer injection methods, their organization and control. Partnership in production.
N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry,
Siberian Branch of the Russian Academy of Sciences
Acad. Lavrentiev Ave. 9, Novosibirsk 90, 630090
Prof. I.A. Grigor’ev, Head of Lab
Tel.: (383) 330-88-50; Fax: 330-97-52
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