Integrated optimization of carbon dioxide enhanced oil recovery and storage under uncertainty.

详细信息   

• 作者：Chen ; Shengnan.
• 学历：Doctor
• 年：2012
• 毕业院校：University of Regina
• ISBN：9780494885826
• CBH：NR88582
• Country：Canada
• 语种：English
• FileSize：6951044
• Pages：214

文摘

CO2 flooding is considered as a promising and practical enhanced oil recovery EOR) process since it not only increases oil recovery,but also reduces greenhouse gas emissions by sequestrating CO 2 in the depleted reservoirs. In a CO2 miscible flooding reservoir,injection of CO2 is often alternated with water,known as water alternating gas WAG) to reduce the mobility contrast between gas and reservoir fluids as well as the degree of viscous fingering. Inappropriate operational parameters for the WAG process can lead to unstable pressure distribution,early gas breakthrough at the producers,and low ultimate oil recovery. On the other hand,CO2 storage capacity can also be affected by the reservoir heterogeneity and operational parameters during the CO2 storage process. In contrast to the commercial CO2 EOR projects of which the main purpose is to maximize oil recovery with a minimum amount of CO2,CO2 storage aims at storing a maximum amount of CO2 in the reservoir. Consequently,optimization of CO 2 EOR and CO2 storage processes differs significantly from current CO2 injection practices,especially in the presence of physical and/or financial uncertainties. In this study,a new optimization technique is proposed and successfully applied to determine the optimal production-injection scheme in a CO 2 flooding reservoir in the presence of the geological and financial uncertainties. More specifically,the controlling variables are chosen to be the injection rates,water-alternating-gas WAG) ratio,cycle time i.e.,the injection time for each gas or water slug),and bottom-hole pressure BHP). Several variable candidates are first assessed,determined and then assigned to each well based on the injectivity or productivity of the well,multiphase flow behavior in the wellbore,and voidage balance within the reservoir. Geological uncertainty is accounted through generating and history-matching multiple equal-probability reservoir realizations i.e.,reservoir models). An objective function associated with both the average net present value NPV) and the uncertainty range of the expected NPV from the multiple reservoir models is defined. A hybrid technique which integrates the orthogonal array OA) and Tabu technique into genetic algorithm GA) is then developed and employed to determine the optimum WAG production-injection parameters. It is shown from a field case study that compared to the un-optimized production-injection scheme,the optimized scheme can be applied to not only increase the expected oil recovery and NPV by 7.8% and 6.6%,respectively,but also achieve a considerably small range of possible NPVs. The newly developed optimization technique based on CO2 FOR scenario is then modified and employed to maximize CO2 storage capacity in a given reservoir. Both CO2 storage capacity with and without water production are investigated and compared. It is shown that,although the storage capacity can only be increased by 2.2% with the process of CO2 storage without water production is optimized,pressure distribution of the optimized storage process is much smoother than that of the reference case. An even pressure distribution will diminish the movement of CO2 underground,thus enhance the security of CO2 storage projects. As for the optimized process of CO2 storage with water production,not only does a much smoother pressure distribution exist compared to that of the reference case,but also the storage capacity is increased by 21.1%.