1 D12 Numerical and Experimental Investigation into the Mechanisms of First Contact Miscible Simultaneous and Slug WAG Injection H. AL-SHURAIQI A. MUGGERIDGE and C.A. GRATTONI Department of Earth Science and Engineering Imperial College SW7 2AZ London United Kingdom Abstract Miscible Water-Alternate-Gas (WAG) injection is currently being performed in many fields around the world and a large number of numerical studies investigating both simultaneous and slug injection including the effects of slug sizes gravity and heterogeneity have been carried out in the past. However there are few laboratory studies to support the numerical work and to understand the interactions between injected