Investigating the cause and proposing solution for the decrease of Productivity Index during water injection in production well using high Calcium brine as drilling mud
Abstract
The paper presents a study conducted by the Vietnam Petroleum Institute (VPI) to investigate the cause of Productiv- ity Index decrease during water injection in a production well that produces oil from a basement reservoir, south east off-shore Viet Nam. The formation of inorganic scale in downhole and near-wellbore of the production well was evaluated using the Scalechem 9.2 software and laboratory equipment modelling a high pressure, high temperature system. The incompatible mixing of injection water and drilling mud losses was found as the main cause of scaling (mainly CaSO4) and the drop of Productivity Index. Based on the scale composition and scale amount, an effective solution has been proposed to remove the scale and restore the Productivity Index, thereby increasing the oil production rate.
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