Monitoring of Polymer flood project at Sanand field of India

摘要

Sanand is the only oil field in India where field-scale polymer flooding is going on for the last twelve years. The field was discovered in 1962 and commercial production commenced from 1969. In view of high mobility contrast and predicted poor recovery of around 15% of OIIP under depletion drive, polymer flooding was adopted as an IOR process for improving oil recovery from this field. An inverted five spot polymer pilot project was started in 1985. Based on the encouraging result of the pilot, the polymer injection project was expanded to a larger area in 1993 and field-scale implementation has commenced from 1995. As on July 2007, the recovery from the field is around 24% with 68% water cut. Envisaged recovery from the field is around 36% with 77% water cut by 2020 with continuance of polymer injection up to 2013 followed by chase water. Maintenance of quality of polymer solution and chase water for such a long period is a real challenge to the professionals associated with the project and plays a key role for the success of the polymer injection project. For this, continuous surveillance of the entire process is required to ensure effectiveness of the project and take mid course correction, if required. The different monitoring aspects involve in the process are-a) performance of producers, b) rheology of polymer at different points of injection system, c) water quality and other parameters affecting the polymer viscosity, such as dissolved oxygen, bacterial activity and d) injection well rate, pressure and performance. This paper aims to present main practices followed for maintaining the quality of injection polymer/chase water and other process parameters and to show how it has helped to improve the efficiency and effectiveness of the polymer IOR technique in Sanand field.