Recently, when controlling the development of oil deposits, extractive companies increasingly use the indicator (tracer) method. The tracer method is based on introducing a predetermined volume of labeled liquid into the control injection well, which is pushed to the control wells by a displacing agent, by the subsequent feeding of the water into the control injection well after the injection of the labeled substance. Simultaneously, sampling is started from the mouth of the producing wells. Selected samples are analyzed in the laboratory to determine the presence of a tracer and quantify it. Based on the results of the analysis, the curves for the dependence of the tracer concentration change in the samples are plotted against the time elapsed from the beginning of the tracer injection for each control production well.

The indicator method is intended for studying the geological structure of the deposit and the filtration flows of the liquid in the reservoir.

Tracer studies can determine:

- hydrodynamic connection between the injection and production wells;

- interplastic flows;

- rate of filtration of the labeled liquid along the bed;

- distribution of filtration flows in the reservoir;

- the permeability of the zones of the formation through which the labeled liquid is filtered;

- the volume of the formation through which the labeled liquid is filtered;

- the contribution of the injected water to the water cut in the production of a specific production well;

- unproductive injection of water pumped into the formation;

- Influence of measures for leveling the injectivity profile of injection wells on the change in filtration flows in the reservoir;

- the effectiveness of various methods of increasing oil recovery by conducting studies before and after exposure.

The technology of carrying out indicator studies takes place in the following sequence. The first stage is the selection of injection wells for pumping tracers and the initial selection of producing wells (in the zone of possible response). Next, a background sampling of the liquid is performed. In the third step, the required amount of trace substances for pumping into each specific injection well is determined, and the labeled liquid is injected into the formation. At the final stage, the production water samples are taken and analyzed for indicator content, and then the data are interpreted.

When selecting indicators for research, the specifics and working conditions are taken into account.

The fluid in the seams moves with a small speed through the smallest channels formed by pore or cracks systems, in contact with the huge surface area of the rock. The rock has a mineralogical composition and often contains elements that help delay the indicator. The pressure and temperature in the deep-lying oil horizons are high. They are saturated with a variety of fluids, and the reservoir waters are usually highly mineralized. All this makes certain specific requirements for the indicators. A substance used to study the movement of a liquid in an oil reservoir must have the following characteristics:

Chemical compounds of the substance must be readily soluble in the traceable liquid and not dissolve in other fluids that saturate the formation.

Maintain its physical and chemical properties in reservoir conditions. Radioactive indicators, in addition, should have an acceptable duration of disintegration, ensuring the performance of the entire set of works in the required facility.

Must not be contained in formation fluids.

They should not violate the natural flow by their presence. Strictly follow along with the hydrodynamic carrier.

With a high accuracy and rapidity, fix in a wide range of concentration changes, starting with a slight. Registration should be done continuously and automatically directly in the trunk or at the wellhead.

Do not pose a hazard to personnel conducting research. Also, the liquid extracted from the formation must be safe. Do not infect terrain and reservoirs into which commercial wastewater is discharged.

Have a value that ensures the economic effectiveness of indicator studies.

To date, it was not possible to name a substance that meets all the requirements for an ideal indicator. Have to use substances that meet at least the basic listed requirements.

But quantum dots are an excellent contender for meeting all these requirements.


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