Abstract

This paper describes a field trial of an optimized Steam Pulse Injection (SPI) scheme in a heavy oil (10-12O API) dual porosity carbonate reservoir located in Egypt. The field is known as Issaran with approximately 1.2 billion barrels of oil in place. Up dip steam injection in selective wells has been applied since August 2009. The fracture network helps upward distribution of steam, heating of the matrix thus wettability change to water wet and release of oil towards the deeper "drainage off take" points. The steamflooding has worked well until the Instantaneous Steam Oil Ratio (ISOR) was getting closer to uneconomical limits. In December 2013, it was decided to test an optimized SPI scheme in the Upper Dolomite South development (old area). Presently the process is working efficiently with oil being drained towards selective low pressure drainage points and in a calculated fashion using IVRR (Instantaneous Voidage Replacement Ratio) controllers. The SPI scheme calls for "On & Off" injection modes. During the "On Mode" injection proceeds normally in all designated injectors. During the "Off Mode" injection continues in few selected injectors. The "Off Mode" injectors are selected on the basis of controlling IVRR around a fault, known as the "magic fault", with the surrounding wells being target withdrawal points for oil production. SPI was designed to reduce operational costs while also benefitting from the pressure release phenomenon, which releases trapped oil from the matrix towards the fracture system and producing wells. During the first 210 days of field trial approximately 823,610 bbls of steam were saved and the ISOR almost halved. The optimization of the SPI will continue and will undoubtedly allow for the extension of the economical life of the field.

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