This paper presents a model that takes into account the transient nature of the imbibition process and the effect of variation in fracture saturation. Gravity effect is included in the calculation of the matrix equilibrium water saturation. This simple method requires only one equation per block per component. This is attained by an analytical transfer function that depends only on the fracture variables and by the assumption of instantaneous pressure equilibrium. The transfer function assumes that capillary pressure is the only driving force of the process and eliminates the matrix saturation from the fracture flow equations. The assumption of instantaneous pressure equilibrium eliminates the matrix pressure. The resulting model has the same form as standard single-porosity models. Results of the new model are compared with those from published laboratory experiments, very fine-grid simulations of matrix/fracture transfer for a single matrix block, and simulation of field-scale water-injection problems by standard double-porosity models. These results demonstrate that the new model provides an economical and accurate means of predicting the performance of fractured reservoirs.
Electromagnetic resistive heating (ERH) is a thermal stimulation technique in which the electrical current passes through formation increasing the original temperature by Joule effect. Thus, greater is the electrical current intensity, highest reservoir temperatures are reached. This method is much influenced by electrical conductivity of the interested zone mainly due to electrical conductivity of connate water. So, water is directly heated by Joule effect and oil is heated by both conduction and convection heat transfer. In this work, it was studied a combination of time heating without production and heating with concomitant production, which provides a greater economic advantage depending on energy price used and oil price produced, since oil production is increased due to heating provided by ERH.This method is suitable for use in wide kinds of reservoirs, with different characteristics of reservoir thickness, injectivity, formation permeability, formation porosity, pressure, depth, temperature, oil saturation and oil viscosity. Depending on the energy magnitude delivered to reservoir and formation pressure, this method can be an alternative to in situ steam generation. For offshore productions systems, where the platform surface is limited, the ERH becomes a quite attractive thermal method, been an alternative to steam flooding avoiding heat losses in pipes.A good strategy for ERH process is, first of all, to choose an electrodes configuration, and after, to control the energy delivered to reservoir, by electrodes voltages, depending of desirable oil rate and temperature obtained in electrodes zones. Electromagnetic resistive heating may produce even better results with water flooding to displace the mobile oil bank after electrical heating, regulating the reservoir pressure and adjusting the electrical conductivity of the system. So, it was possible to optimize the operational parameters to maximize the oil recovery with minimal energy requirement, resulting in an economic advantage.In this work, it was studied an application of Electromagnetic Resistive Heating in a reservoir with similar characteristics of those found in Brazilian Northeast Basin. The obtained results can be extrapolated to others important applications, for example, offshore heavy oil reservoirs, where, actually, there is no available technology to exploit them.
There is still a large amount of natural resources in heavy oil reservoirs which can be explored using new methods. However, this enormous amount of hydrocarbon resources which are in these reservoirs may be explored with new concepts. The VAPEX process is a promising recovery method. The process consists in two horizontal wells, parallel between themselves, producer and injector, where vaporized solvent is injected with the objective of reducing the oil or bitumen viscosity. The purpose of this work is to examine how some important operational and reservoir parameters influence the VAPEX process, in the produced oil rates, in the cumulative produced oil and in the recovery factor. Parameters such as the spacing between wells, the injection pressure, and type of solvent, oil viscosity, residual water saturation and horizontal permeability are addressed in this study. The choice of solvent to be used in the process was the factor that most significantly influenced the process, allowing a greatest recovery factor of oil. The largest cumulative oil recovered was obtained for other parameters of significant influence as the longest distance between wells, increased horizontal permeability and lower injection pressure. Introduction The exploitation of heavy oil or bitumen is of interest to many oil companies due to the decline of conventional oil reserves. These resources worldwide are in the order of 1 trillion m3 (about 6 trillion bbl) of oil in place, which is about six times more than the total reserves of conventional oil, where most is present in Venezuela. Canada is second with estimated oil in place of 400 billion m3 (2.7 trillion bbl), double the total deposits of conventional oil in the Middle East (Janisch, 1979). In many reservoirs, the high viscosity oil limits the primary production so the need to improve methods of recovery of oil. Currently, the thermal processes are implemented as a process of enhanced oil recovery for recovering heavy oil. But little by little, the miscible methods are also being indicated. The recovery by heat-based methods may be more problematic and uneconomical for some scenarios, such as reservoirs with gas cap, aquifer, high water saturation, low porosity, low thermal conductivity, small thickness, vertical fractures and / or cracks, and required other methods of recovery. In oil reservoirs where there is low efficiency of displacement and fluid injected cannot extract the oil from pores of the rock due to high interfacial tensions, the use of miscible methods may be recommended. Among these advanced methods of recovery can find the process VAPEX (vapor extraction) process that is under development as an alternative to thermal processes such as injection of steam. VAPEX process for recovery of heavy oil has attracted much interest in recent years due to the fact that steam is not used in the method. In Canada, for example, several oil companies are actively participating in developing the VAPEX process, which is advancing rapidly with the purpose of marketing them. Some of these companies are at Plover Lake, in Cold Lake, in Foster Creek, in Fort McMurray, all in Alberta, and in North Carruthers has implemented the process in pilot areas (Upreti, 2007). The impact of the spacing between the injector and the producer with and without gas cap was discussed by Karmaker et. al (2003). Das and Butler (1996) suggested that the propane and butane are the most effective solvents for VAPEX and proved that the diffusion of propane is more rapid than that of butane. The objective of this study is to analyze the process VAPEX through operational and reservoir parameters, and thus determine which parameters have significant influence in the process.
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