On the solubilization effect as a key factor in the cluster discharge of associated produced water

Introduction. In order to reduce operating costs during the transportation of ballast produced water at the X field located in the Ural-Volga region, the oil company conducted pilot field tests of a sump well that performs preliminary cold discharge of produced water directly at the well pad of this field. The commissioning of the «sump well» was carried out by changing and regulating the operating mode of the pumping equipment using a frequency-controlled drive, as well as by limiting the flow of liquid to the reception of the sump well. However, during these pilot field tests at the «sump well», the quality of the discharged water in terms of the residual content of petroleum products according to Industrial Russian standard OST 39-225-88 was not achieved in order to further implement the reservoir pressure maintenance system.

Aim. The purpose of this work was to determine the root cause for which it is impossible to achieve the required quality of discharged ballast produced water according to Industrial Russian standard OST 39-225-88 with the established design technological parameters.

Materials and methods. The thermochemical method of gravitational sedimentation called Bottle test was used as a research method to determine the residual content of petroleum products in water over time of gravitational sedimentation. In addition, the stalagmometric method (using the stalagmometer called Rubin-02A) was also used to simulate the reduction of interfacial tension at the oil-water interface using a demulsifier and a corrosion inhibitor, which were used at the object of the study. The identification of the critical concentration of mycelium formation and confirmation of the solubilization effect was carried out using a stalagmometer called the Rubin-02A trademark.

Results. During the analysis of field data, lab and pilot works, it was revealed that one-time well treatments with a corrosion inhibitor and a demulsifier lead to a significant decrease in interfacial tension at the oil-water interface, and as a result, a solubilization effect occurs. With the resulting solubilization effect, it is impossible to achieve standard water quality values for the content of residual petroleum products in water, even taking into account a significant increase in the time of gravitational sedimentation.

Conclusion. The obtained results of the work will make it possible to adapt the application of cold discharge technology of associated produced water using a «sump well» at the late stages of oil field development. 

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