Drilling, Completion and Well Intervention operations generate waste water. With the increasing volume of well fluids being flowed back due to aggressive Well Intervention activities, there was a need to handle and dispose the waste water efficiently. This was required to maintain continuity of well flow back and stimulation operations in an efficient and sustainable manner without incurring additional cost keeping in mind the current Oil and Gas market scenario.

This paper presents the "Best out of Waste" methodology adopted by the Well Services Department of Cairn India Limited to manage the huge waste water volumes by pooling in-house resources for developing Waste Water Treatment Project.

This project as it stands today was brought together by first, evaluating various treatment methods such as EC (Electro Coagulation) unit, Chemical methods, Particle settling and Disposal methods such as natural evaporation, evaporators (Mechanical and Solar) and injection and further combining features of the above stated methods to gain maximum benefit. These evaluations led to selection of EC Unit combined with the effectiveness of Mechanical evaporators and Natural evaporation for decreasing the waste water footprint.

Second, identifying a disposal well for treated water injection, established by various integrity and injectivity tests to confirm that the well was ready to accept the water with parameters and properties similar to that of EC unit output. The encouraging results in the injectivity tests proved to be the kick-off point of the project. Continuous monitoring of the treated water was also done to ensure the TSS and oil in water remained within the acceptable limits for injection, as per prevailing norms.

Third, developing disposal pits and tank farm to facilitate the treatment and dumping of the treated waste water. Lastly, decreasing current waste water inventory along with reducing the OPEX involved with handling, transportation and disposal of the waste water.

The key feature of this project was the utilization of above mentioned equipment's from internal resources of the company, which were either working stand-alone or were nonfunctional. Thus, the CAPEX for the project was brought to a bare minimum.

The objective of this paper is to present the various technical, administrative and commercial aspects associated with this project and conclude with plans of further utilizing the treated water for future Fracturing, Stimulation and even completion jobs.

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