Screening criteria for enhanced oil recovery in carbonate reservoirs
Creators: name: Al-Hajri, Naser F.
Publisher: name: Imperial College London
Year: 2010

description: Oil production from EOR projects continues to supply an increasing percentage of the world‟s oil. About 3% of the worldwide production now comes from EOR [1]. To ensure the future supply of oil, more research needs to be done to determine the optimal method of increasing the recovery from mature known field. In this thesis we have developed screening criteria to maximize oil recovery using different EOR strategies. Water flooding in heterogeneous and stratified oil reservoirs often yields only low average oil recovery (around an average of 35% globally). Recovery with conventional injection systems is imperfect due to the incomplete sweep of the reservoir space. There are two factors affecting the recovery one is the pore scale recovery, limited by interfacial tension and the other is areal and vertical sweep efficiency limited by the heterogeneities, therefore it is logical to try to improve this recovery . Oil recovery frequently involves the injection of fluids into oil field reservoirs in an effort to drive the oil toward the production wells. Various drive fluids including fresh water, re-injected oil field brines, polymer solution, carbon dioxide, surfactant, flue gases and steam are used for this purpose. Limited numbers of EOR methods have been used in this study based on the properties of the reservoir and the screening criteria done from different studies. While the mechanisms may differ significantly, these recovery methods have proven to improve oil production in many reservoirs [2]. Reducing the mobility ratio between water and oil, especially by increasing the viscosity of the injected water to reduce and manage efficiently the water produced, is one of the most popular methods to enhance the oil recovery. Significant water production is a serious problem in the petroleum industry. While this problem can arise for several reasons, water production from high permeability streaks or channels during water flooding operations is a common cause. Excessive water production can not only reduce the project economics by excessive water treatment and disposal cost but also can completely prevent the production from gas and oil wells, from which the production has become uneconomic. The need for effective EOR technologies in the oil industry will become more urgent in the future, as mature fields will be affected by pressure drop and water production. Therefore, using some other alternative like polymer, solvent, and surfactant injection will help to increase the production and reduce the water production. Optimizing the recovery using different EOR technologies will help also to decrease the water production in the system. This study was done based on changes of the concentration of the injected agent and the slug size. Different concentrations and slug sizes can improve the strategy used from a low recovery to a very high one. The uncertainty of the oil price and geological heterogeneity (for example permeability distribution) can also change the optimal choice of EOR scheme and then the order of the preferred technology from one to another. A sensitivity analysis was done to validate the outcome results and make sure that the project is still profitable as the parameters changes on specific ranges.