3.3.2 Weyburn and Midale Oil Fields

CO2 injection has been widely applied for enhanced oil recovery (EOR) purposes at more than 70 sites worldwide. Injection of CO2 into the Weyburn Oil Field of southeast Saskatchewan, Canada, began in 2000 with the intention of reversing the decline in oil production. After 10 years of CO2 injection, oil production in this 50 year old field has increased by 60%. Moreover, it has been estimated that about a further 155 million barrels of incremental oil may be recovered that will extend the life of the field by more than 30 years. Similarly, in the adjacent Midale Oil Field, full field CO2 injection began in September 2005 with a forecast 60 million barrels of incremental production over a period of 30 to 40 years. The Great Plains Synfuel Plant near Beulah produces 13,000 tonnes of CO2 daily as a by-product of lignite gasification, 60% of which (8,000 tonnes) is injected in the Weyburn and Midale Fields. More than 18 Mt of greenhouse gases are currently stored in these two depleting oil fields, with an expected ultimate combined storage of around 40 Mt CO2 (Whittaker et al., 2011).

A research program has been developed for the Weyburn EOR project with the aim of achieving a better understanding of the processes associated with long-term geological storage of greenhouse gases. The programme has four main themes: 1) geological characterisation; 2) prediction, monitoring, and verification of CO2 movements; 3) CO2 storage capacity and distribution predictions and application of economic limits; and 4) long-term risk of the storage site. Different aspects of the EOR project have so far been studied in over 50 research projects. Within the Weyburn-Midale region (40 x 50 km) there are more than 4,000 wells that penetrate to reservoir-level depths. Due to the large number of wells in the study area, a less conventional approach to flow modelling - invasion percolation methodology - has been employed. The invasion percolation model constructed for Weyburn contains 2 billion cells of 20×20×5 m. During the initial phase of the project (2000 to 2004), a deterministic numerical simulation approach was used to model the migration of the injected CO2 for 5,000 years. A significant number of publications have been generated from the studies including recently published papers in the GHGT-10 conference (Hawkes et al., 2011; Rostron and Whittaker, 2011; White and Team, 2011). During the Weyburn final phase project, the evolution of reservoir brine chemistry has been studied and is used to show the role of fractures in controlling flow. This is expected in forthcoming publications.