An oil well in Japan, referred to in this paper as Well B, experienced emulsion problems from the commencement of natural flow production in January 2008. These problems were immediately resolved by the usage of effective demulsifier which was selected through bottle tests. As the well ceased to flow naturally in April 2014, an artificial lifting operation began with a jet pump since July 2014 to maintain the production rate. Shortly after artificial lifting performed, serious emulsion problems recurred even though it was continued to utilize the demulsifier which had worked successfully during natural flow. This paper presents the details of how we addressed these problems and managed to continue operations. Temperature, retention time and chemical injection were well known as the factors for separating emulsion. First, plant operator planned to raise the processing temperature from the current operating condition of 60°C. However, it was found that temperature higher than 60°C could damage coating inside gun- barrel and tanks which were located downstream of the second separator. Through fine optimization, the processing temperature was set at 65°C not to expose them to higher than 60°C but this was not feasible to separate emulsion. Second, we changed the flow scheme of two production separators from parallel to series connection. This countermeasure didn't resolve these problems essentially but it enabled us to catch almost all emulsions at the first separator. It means that the first separator condition could be reset by draining emulsion periodically from dump valve so that we managed to continue operations with keeping the target water content in sales oil. Finally, a series of bottle tests were conducted to select a better demulsifier to replace the original one, which was no longer effective. Soon after injection of the new demulsifier, the emulsions disappeared and the operator regained the production rate. This improvement reduced the emulsion disposal cost and man-hour for treating emulsions. Furthermore, oil which had been disposed as emulsions could be sold as product and Net Present Value (NPV) of this asset increased through high production rate operations. The total amount of economic impact reached 2 million dollars.
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