Abstract
The whole industry seeks to extend the economic life of existing brown fields, due to the difficulty of discovering new giant assets. The efficiency of mature waterfloods may be drastically improved by means of new technologies in order to recover a significant amount of unswept oil. IOR and EOR processes were investigated to increase oil production in a giant brown field in North Africa, developed by means of peripheral sea water injection. Current water injection scheme shows not optimal sweep efficiency and moderate recovery factor due to geological heterogeneity and unfavorable mobility ratio. This work describes the efforts to maximize water injection efficiency by means of the combination of different IOR and EOR techniques with focus on low salinity water.
A dedicated plan to enhance water injection was implemented considering the following pilots: a) water conformance by Thermally Activated Particles (TAP) tested in 2009 and extension planned 2015; b) polymer flooding started in the second half of 2015; c) Low Salinity (LS) water flood planned for 2016. In addition, the combination of the above technologies is under study and will be further evaluated based on the results of pilots.
LS water benefits were investigated within a comprehensive EOR study. First, tertiary corefloods on porous media were performed, showing an evident EOR effect compared with sea water, in increasing the oil recovery up to 7%. Modeling and uncertainty quantification studies showed that LS water may have a significant potential and can be synergically combined with polymer injection to maximize production. A sequence of Single Well Chemical Tracer Tests (SWCTTs) was performed in the second half of 2014 to quickly evaluate LS performance at the well scale resolution. Cycles of injection, shut-in and production periods were performed on a selected well to measure the residual oil saturation (Sor) after sea water and LS water. Promising results were achieved for LS, showing a considerable reduction in residual oil, of about 5-11 saturation units (s.u.) compared to sea water. The SWCTTs were used as a powerful tool to achieve a quick EOR response and confirmed low salinity potential.
The next phase foresees an interwell pilot to test the technology at a larger scale, whose design is currently ongoing. Moreover, the opportunity to optimize the existing polymer injection in a Low Salinity Polymer (LSP) treatment is under study to increase production and reduce project costs.