Simulation Study on Surfactant Flood Performance in a Segment of the Edvard Grieg Reservoir
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The purpose of the work done during this project is to provide an overview of the topic of Surfactant EOR and to evaluate the effect of a Surfactant flood on reservoir recovery in a segment of the Edvard Grieg field. The theoretical background needed to evaluate the effects of a surfactant flood is based on a review of the literature available on the topic and is presented in the first part of the report. The second part shows how this theory can be used to conduct a simulation study in Eclipse 100 based on a synthetic model of a segment of the Edvard Grieg field with four wells: two injection wells and two production wells. The STOIIP of the model is 19831910 $Sm^3$. The results of a sensitivity analysis that optimizes the injection process based on factors such as incremental recovery factor and chemical efficiency are used to evaluate the effectiveness of the surfactant process compared to a base case waterflood. Further analysis of uncertainties and a simplified economic DCF study is conducted to form a conclusion on the feasibility of surfactant flooding for this segment. The field possesses the necessary characteristics for a surfactant flood to be successful. It is a sandstone reservoir containing light oil and is already being produced with water injection as the main drainage strategy. Initial core flooding tests have shown a significant reduction in residual oil saturation to 9 \% by injecting surfactant after first being decreased from 30 \% for normal waterflooding to 26 \% for low salinity water.The main factor that might work against a surfactant flood in this segment is a large well spacing and high additional capital and operational costs compared to an onshore application. A base case injection of a 1 wt \% surfactant solution for seven years led to an incremental recovery over waterflood of 1494746 sm3, corresponding to a 7.537 \% increase in recovery. A chemical cost of 103.7 \$/sm3 showed that although the production increased by a significant amount, it would still not be economically feasible. The optimization study found that a 0.5 \% surfactant concentration injected over 10 years was the optimal case for technical evaluation parameters giving a chemical efficiency of 91.25 kg surfactant needed for the production of one cubic metre oil and a cost per barrel of 53.5 \$ at zero discount rate. Evaluation by NPV showed that all projects would lose money and found another optimum as the case with the least negative NPV value of -96275326 \$. This was for the 0.5 \% concentration slug injected for four years. For further study it is recommended to conduct the simulations with surfactant input data gathered from laboratory tests as uncertainties in these values will have large impact on efficiency of the flood. Investigation of slugs at even lower concentrations should also be investigated further if a surfactant that can effectively reduce IFT at low concentrations can be found for the reservoir environment. The results should also be related to a larger model and a more detailed economic analysis should be conducted to accurately estimate the feasibility of the different slug designs.