Enhanced Oil Recovery (EOR) Technical Concepts In an effort to minimise their dependence on imported oil, China is attempting to maximise the contribution their domestic oil reserves make to their total oil supply. As such, a primary focus is on improving the performance of existing oil fields, by using technical recovery methods, known as EOR, to access reserves that were previously unattainable due to geology or expense. EOR is chiefly concerned with affecting the mobility of the oil through the drilling process, late in the life span of the well. It primarily does this through the use of injecting fluids in the drilling process. EOR processes can result in 30-60 per cent or more of the reservoir’s original oil being extracted, compared to just 20-40 per cent using primary or secondary recovery methods. Note: The volumetric sweep efficiency at any time is the fraction of the total reservoir volume contacted by the injected fluid during the recovery. When using water, consideration of the mobility of the fluids is an important factor when determining the area and vertical sweep efficiencies. This would help to determine the mobility ratio. If M is less than one (1), then oil is capable of travelling at a rate equivalent to the water. An increase in the viscosity of the oil would mean that M would increase and this would lead to the injected fluid moving around the oil. This would also make it harder for the oil to penetrate the pore. To improve this ratio, the viscosity of the water has to be increased. When M is greater than one, the displacing fluid has greater mobility than the displaced fluid. Also the position of the water injection and the flooding patterns would go a long way to determining the recovery patterns. Another point to consider in oil recovery is the position and orientation of the injection wells around the production well. As the mobility ratio increases, the sweep efficiency decreases. Once a channel of water exists between the injector and the producer, then little additional oil would be recovered.
