At present time, a mature oil reservoir generally has a secondary or enhanced oil recovery process in order to increase production or reserves. That process generates important field information as pressure, production, fluid being injected, and fluid being injected that is produced at surface, among others. This information is useful for others reservoirs with similar geologic properties allowing better recovery factors and increasing oil production.

Injection of nitrogen in the gas cap of the Akal field in Mexico is taking place to maintain pressure in the reservoir. Around the world, there is not enough experience in nitrogen injection in reservoirs with industrial volumes. From this, the necessity of nitrogen control methodologies and procedures arise in this area and extend them for use in other fields.

This paper presents a procedure of sampling and analysis of nitrogen concentration in the field including wells, platforms, separation facilities, gas pipes, and delivery points. This is based on more than 20,000 samples of gas chromatography from gas being produced. The samples are recovered in strategic points by a team work in sampling, chromatography, and data analysis. Sampling and chromatography analysis help to identify the increase or decrease of nitrogen concentration. Additionally, production of nitrogen in gas being produced affects negatively the gas quality.

Additionally, simulation of gas flow pipelines including gas production from other fields, and the presence of high values of nitrogen mol concentration in wells helps to determine the nitrogen concentration in the gas delivery point.

Due to Akal field is a naturally fractured oil reservoir with high density of fractures, nitrogen being injected travels rapidly toward the oil gas contact. Then, nitrogen is used as a tracer for dynamic reservoir characterization. Determination of nitrogen mol percent for each well allows us to know qualitatively the development of the gas cap of the reservoir.

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