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Abstract Several processes for improved oil recovery are thermal and are based on steam injection. Through these methods is possible to heat the reservoir, reducing oil viscosity and increasing the oil-phase mobility, allowing a better oil displacement in reservoir and increasing swept efficiency. Nowadays, one of the most promising thermal recovery technologies is Steam Assisted Gravity Drainage (SAGD). In this process, two horizontal wells, separated by a vertical distance are placed near formation bottom. Horizontal top well is used for steam injection, which creating a steam chamber which grows upper and to surroundings allow heat transfers between steam and oil by conduction. Bottom well is used for oil production. SAGD process appears to be technically attractive, due to the high recovery and highs oil rates and oil-steam ratio. This process was applied in country such U.S.A., Canada and Venezuela. In this work, it was idealized a reservoir with some northeast Brazilian characteristics in a homogeneous model. It was done an optimization of steam rate, in a non continuous form, injected steam for several time periods. For the optimization study was also realized a net present value study and it was compare to a process with continuous steam injection. All the cases studied were done using the software STARS from CMG (Computer Modelling Group). This study showed that, in SAGD process, steam requirement can be reduced by injecting it in a non continuous form, alternating steam injection with stops at several time intervals. It was possible optimized these intervals minimizing heat losses and improving oil recovery. The optimal time interval was found at six months that mean, it can injected steam for six months and then stops the steam injection for next six months. When it was compare to a system with continuous steam injection, was founded that this system had a lower net present value that the system with steam injection with stops. It was founded that was possible to reduce water production, with an improved of oil recovery. In this work was obtain a way to optimized steam rate, minimizing heat losses and increasing net present value, in reservoirs with some Brazilian Northeast Basin characteristics, and that become important, because it is necessary to improved heavy oil recovery with minimal environments damages, and with lower production cost. Introduction Steam assisted gravity drainage (SAGD) and its variations are technologies considered now effective in the recovery of heavy oil and of bituminous sands. This method involves two horizontal parallel wells separated vertically by a short distance, where the top well serves as steam injector and bottom well picks up reservoir water, condensed water and the heated oil. Gravity is the acting force in this process. When steam is continually injected at the top well, oil is heated up and forms a steam chamber that grows upward and to the surroundings (Butler, 1991). Temperature inside steam chamber becomes essentially equal to steam injected temperature. Steam condenses at the interface with cold oil and heat is transferred to the oil. Then, heated oil and the condensed water drain by gravity, until the producer horizontal well located at the bottom of the reservoir.
- South America (0.88)
- North America > Canada (0.49)
- North America > United States (0.34)
Optimization of Operational Parameters on Steamflooding With Solvent in Heavy Oil Reservoirs
Pinheiro Galvao, Edney Rafael Viana (Universidade Federal do Rio Grande do Norte) | Rodrigues, Marcos (UFRN) | Barillas, Jennys Lourdes Meneses (U. Federal Rio Grande do Norte) | Dutra, Tarcilio (Federal University of Rio Grande do Norte) | da Mata, Wilson (U. Federal Rio Grande do Norte)
Abstract The process can be understood as a combination of a thermal method (steam injection) with a miscible method (solvent injection), promoting, thus, reduction of interfacial tensions and oil viscosity. When co-injected with steam, the vaporized solvent condenses in the cooler regions of the reservoir and mixes with oil, creating a zone of low viscosity between steam and heavy oil. Mobility of the displaced fluid is then improved, resulting in an increase of oil recovery and oil rates. To better understand this improved oil recovery method, a numerical study of the process was done contemplating the effects of some operational parameters (distance between wells, steam injection rate, solvent type and injected solvent volume) on cumulative oil produced and oil rates. Simulations were performed in STARS (CMG, 2007.11). Semi synthetic model was used in this study and some reservoir data were obtained similar to those found in Brazilian Potiguar Basin. The method presented good performance for heavy oil reservoirs with approximately 200 m depth, porosity between 20% and 30%, vertical/horizontal permeabilities ratio of 10% and thickness around 30 m. It was found that injected solvent volumes increased oil recovery and oil rates. Further, the majority of the injected solvent was produced and can be recycled. For applications of optimized model with oil viscosities of 300 cP, 1000 cP and 3000 cP, the most important oil recovery was obtained for the lightest one (300 cP), while for 1000 cP and 3000 cP, the final recovery was practically the same. The high initial productions achieved by models that use solvent as an advanced recovery method have normally a significant impact on the operation economics, because early production suggests that fluids injection (steam and solvent) can be interrupted earlier. On environmental point of view, solvent injection can provide a reduction of energy and also a reduction in water consumptions for steam generation, having diminished Green House Gases (GHG) emissions. Also it is important to emphasize that the higher oil rates presented by these models can generate an earlier financial return and, by consequence, a project with a good economical viability. Introduction In several world-wide reservoirs, the high viscosity of crude oils presents a serious challenge for their recovery. With the decline of conventional oil reserves, attentions have turned to heavy oil production, in which the technology approach is generally based on viscosity reduction through the use of thermal energy. From several thermal methods used by oil industry, Steamflooding has been one of the main alternatives to increase heavy oil recoveries. This method consists of injecting heat in reservoir, increasing oil mobility and facilitating its production. To increase the efficiency of this mechanism, a resource more and more used is the addition of solvents, hydrocarbons well known for reducing interfacial tensions and facilitating the production of heavy oil. When co-injected with steam, the vaporized solvent condenses in the cooler regions of the reservoir and mixes with oil, creating a zone of low viscosity between steam and heavy oil (Shu and Hartman, 1988). Mobility of the displaced fluid is then improved, resulting in an increase of oil recovery and oil rates (Galvão, 2008).
- Research Report > New Finding (0.66)
- Research Report > Experimental Study (0.47)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)