oa Novel Technique for Tar mat identification and mapping

Tar mat identification and mapping has been a challenge for the oil industry for years. Limited number of techniques and tools are available to identify tar presence in an oil field. These can be divided to three main categories: • Laboratory based on drilling cuts, core or side cores in suspected tar zone. • Log based, using mainly NMR and Formation Tester • Surface and borehole Seismic. Each of these three main techniques has its own advantages and disadvantages. The first two techniques suffer from limited availability across the field to allow mapping of tar. Furthermore, NMR logs also have difficulty distinguishing tar from heavy oil as both show similar NMR characteristics. Surface and borehole seismic on the other hand are excellent tools for mapping but lacks the ability to accurately identify tar mats. The Novel technique proposed in this paper combines cheomstratigraphy, NMR, formations tester, geochemical logging and borehole seismic to identify and map tar mats. The main concept behind the new technique is to link tar identification to three independent measurements chemical, NMR and acoustic to overcome limitation associated with each technique. Then use borehole seismic to map tar mats based on the tar attributes defined by laboratory and wireline acoustic measurement. The technique is implemented in three main stages first identifying tar and separating it from any heavy oil that might be associated with it. Second stage, is finding the tar cheomstratigraphic finger print that can be linked to a geochemical log. This stage will allows identification of tar map thickness in well by well bases. The third and final stage, is linking tar acoustic properties measured in both laboratory and wireline to borehole seismic attributes then surface seismic to map tar across the field.