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Below are the field cases in which applied power was reported together with the oil production increase, so that we can evaluate and compare the energy gains of the different processes tested. Comments The EG calculation assumes that the power reported is the 60 Hz power of the HF power supply. Data reported by Pizarro and Trevisan Comments Test stopped after 70 days of heating because of voltage control system problems. Comments Both wells were badly sanded, and operations were suspended. There was a history of short circuits and power supply problems (casing isolation failure suspected).
A new device that heats thick oil sands crude with radio waves is being used for the first time in a production well in western Canada. Rather than pumping steam into a well to reduce the viscosity of oil as thick as peanut butter, the new method combines an electromagnetic heating element and a solvent to mobilize the crude at a much lower temperature. Suncor Energy is leading the four-company group doing the pilot with support from the province of Alberta, which is backing projects developing affordable ways to reduce emissions from oil sands operations. The pilot began by heating the well using a specially created antenna from Harris Energy Solutions. The US defense contractor used what it has learned to reduce the heat emitted by military communication devices in a totally different way.
Ji, Dongqi (China University of Geosciences) | Harding, Thomas Grant (University of Calgary) | Chen, Zhangxing (University of Calgary) | Dong, Mingzhe (University of Calgary) | Liu, Hui (Computer Modelling Group) | Li, Zhiping (China University of Geosciences) | Lai, Fengpeng (China University of Geosciences)
Abstract For methods of thermal heavy oil recovery, an alternative approach of applying electrical energy, such as electromagnetic heating, can be used to generate heat in reservoirs that are not suitable for steam injection or to improve the economics and reduce environmental impact of the heavy oil recovery compared to using steam injection. While much progress in the development of electromagnetic heating technology has been made in recent years, the ability to accurately and effectively mathematically model the application of an electromagnetic heating process to a reservoir has been limited. In this paper, based on our reliable and efficient electromagnetic heating simulator, the effects of operational parameters on electromagnetic heating performance are investigated including evaluation of antenna location, well constraints, and applied power and frequency. The feasibility of electromagnetic heating in oil sands reservoirs has been examined for two cases: a) a single horizontal well containing a heating source and b) a horizontal well-pair with heating sources located in both wells.
Cesar, Ovalles (Chevron Energy Technology Co., California, USA) | Pedro, Vaca (Acceleware Inc., Calgary, Canada) | Gunther H., Dieckmann (Chevron Energy Technology Co., California, USA) | James, Dunlavey (Chevron Energy Technology Co., California, USA) | Ronald, Behrens (Chevron Energy Technology Co., California, USA) | Lee, Dillenbeck (Chevron Energy Technology Co., Houston, USA) | Michal, Okoniewski (Acceleware Inc., Calgary, Canada)
Abstract Downhole RF heating continues to be the interest of the petroleum industry because of its advantages over conventional forms of heating. Previous results have shown that without a low-loss dielectric zone (LLZ) around the downhole RF emitter, none of the available linear dipole antennas can work efficiently, and most of the energy is absorbed preferentially in a few meter radius around the radiating well and will not penetrate substantially into the reservoir. To circumvent this problem, low-dielectric materials were proposed, which are composed of a solid mixed with an appropriate binder. These materials were selected to have low dielectric properties so that the RF absorption is minimized, and at the same time, low porosity to prevent water invasion during the RF heating operation. Four solids, Ottawa sand, solvent deasphalted tar, Poly(p-phenylene sulfide) (PPS) and Polyether ether ketone (PEEK) and four binders (polydicyclo pentadiene (DCPD) and phenol-formaldehyde resins (Novolac), a C-Class cement slurry, and a foamed cement) were evaluated by measuring their dielectric properties (dielectric constant and loss tangent) in the frequency range 1 - 2000 kHz and temperatures between 25–200°C. All four solids have low RF absorption as well as low porosity (<1%), and those values did not change significantly with temperature. Also, smaller dielectric properties were found for DCPD and Novolac than those found for the cement materials, and the DCPD binder has a dielectric constant almost half and a loss tangent one order of magnitude lower than those measured for the Novolac resin. Three different designs for the construction of LLZ were considered, which included underreaming the oil well, squeezing a solid-containing binder downhole, and creating a casing-less completion. Numerical simulations show that the use of a low-loss zone around the central emitter leads to a very much improved energy and temperature distribution, and higher penetrations (~12 m) than the case without it.
In the modeling of any system, one is always faced with the dilemma of choosing the level of complexity that correctly predicts the response of interest. In the case of modeling the electrical heating of wells and reservoirs for heavy or extra-heavy oil at low frequencies (below the microwave range) and considering only one liquid phase and no gas phases, the systems of equations shown in this article are considered sufficient. The problem is still unsolved for the case of microwave heating of reservoirs, in which a complete model, which correctly takes into account the electric losses of a system of solid grains, liquids with dissolved gases and salts (with the corresponding complex geometrical, scaling, and electrochemical properties in the presence of electrical diffusion currents and space charges), is not yet available. For the case of concentrated heating (either resistive or inductive) and distributed heating in the reservoir and surrounding regions (at frequencies below the microwave range) or distributed heating in the metal elements (at any frequency) the equations given next (in a cylindrical coordinate system) are deemed sufficient. The third term on the left, the product of temperature multiplied by the divergence of the velocity, has been neglected in many models of heating of reservoirs (it is strictly zero only for incompressible fluids.).
Electromagnetic heating has a different effect on heavy oil reservoirs than other enhanced oil recovery processes that use heat. This article describes the ways in which electromagnetic heating can be applied to a reservoir. As shown in Figure 1, Q(t), the time-dependent rate of production of a given reservoir with either horizontal or vertical wells, depends on the flow of oil through the reservoir and through the producing wells. In the reservoir, the flow is conditioned by a temperature-dependent viscosity, μ(T), porosity, permeability, and compressibility (Φ, k, and c). To a first approximation, the last three parameters are unchanged by the heating.
The electromagnetic heating of oil wells and reservoirs refers to thermal processes for the improved production of oil from underground reservoirs. The source of the heat, generated either in the wells or in the volume of the reservoir, is the electrical energy supplied from the surface. This energy is then transmitted to the reservoir either by cables or through metal structures that reach the reservoir. The main effect, because of the electrical heating systems used in practice in enhanced oil recovery, has been the reduction of the viscosity of heavy and extra heavy crudes and bitumens, with the corresponding increase in production. Focus is centered on systems (and the models that describe their effects) that have been used for the electromagnetic heating in the production of extra heavy petroleum and bitumen.
Abstract Onsite recovery of heavy-oil is primarily done by thermal methods. The aim of these methods is to reduce viscosity of heavy oil to deploy it towards injection well. Unfortunately, these methods maybe inadequate for certain economic criteria and subject to environmental limitations. Additionally, they may not be compatible with certain types of reservoirs, examples: shales, deep reservoirs, etc. Recently, interest was devoted to electromagnetic heating with radiofrequency (RF) to overcome some of these problems. A theoretical model has been provided for Heavy Oil Recovery through RF waves which compete with the existing methods of EOR by thermal heating. A set of governing equations has been provided with an experimental model that proves the method more efficient than others. As a result, the interaction of an oscillating polar molecule with its neighbours takes place and it generates frictional heat, which raises the temperature of the medium. In general, the EM heating process relies on preferential absorption of EM energy as the means of increasing temperature of dielectric materials. The ability of an EM wave to conduct energy to a medium is determined by the molecular composition of the medium. If the medium holds mobile molecules with molecular dipole moments, then torque is exerted on the polar molecules by the passing Electromagnetic waves and the alignment of dipole moments with the oscillating electric fields of the electromagnetic waves take place. As a result, the temperature of the medium is raised due to heat generated by friction as continuous encounters between oscillating polar molecules happen. Microwaves are very much effective to produce heat by getting sufficiently absorbed by the materials. Since crude oil is not a good absorber of microwaves, microwave receptors like activated carbon, nano-metal oxides, and polar solvents should be used to make the microwave process faster. Hence, further research is needed to implement the enhanced metal-nanoparticle incorporating electromagnetic heating (EMNIEH) at the field scale. In this case, the main question is how to inject nanoparticles into reservoir through the wellbore hole during EM heating. Electromagnetic Heating is very much a substitute to aqueous thermal EOR methods for heavy oil recovery from shale reservoirs or high clay content or deep reservoirs. This technology can also be implemented in complex geological system as it is relatively less expensive and better for the environment. A theoretical model allows us to take stock of how we can optimize and increase the use of EM waves and RF to efficiently deploy it onsite.
Abstract Heat generation in the reservoir by means of electromagnetic wave stimulation offers innate advantage with efficient energy introduction. Transmissibility of heavy oil and bitumen are predicated on decreased viscosity through temperature rise, which makes microwave heating a plausible candidate. This study focuses on identifying the components of the crude oil which primarily contribute to heat generation under the influence of the microwave. Pinpointing what makes the oil a more effective microwave receptor enables the optimization of desirable traits in the oil phase. Three different oil samples were selected due to variations in both physical and dielectric properties. Fractionations were then performed on each oil to isolate the contribution of each SARA (saturates, aromatics, resins, and asphaltenes) constituent. Dielectric constant and loss index, which together represent complex permittivity, were measured by utilization of a vector network analyzer (VNA) with a dielectric probe. Complex permittivity of both the bulk oil as well as each fraction were measured for all three oil samples. Also, investigation into asphaltenes behavior in the oil, either precipitated or dispersed, was performed by introducing varying dosages of both precipitating agents (nC5, nC7) and a dispersant (toluene). Within the oil phase, the mutual attraction that is realized by the more polar components, namely the resins and asphaltenes, creates complexities in the absorption behavior. Net cancellation of the individual polarity is evidenced by the non-additive nature of the deasphalted oil and asphaltenes. The attraction between the resins and asphaltenes is further illuminated by inspection of the dielectric response in the presence of the precipitating agents. Removal of asphaltenes through precipitation corresponds to the freeing of interacted resins. The contribution in polarity of the previously cancelled resins is evidenced by an increase in the dielectric constant with increasing precipitating dosage. Both oil C2 and C3 achieve the identified behavior stemming from an asphaltene weight percent comparable to that of the resins. However, upon analysis of the oil C1, the opposite trend is achieved. Unique to oil C1 is a very large weight percent of asphaltenes. Therefore, the oil has excess asphaltenes which aren't interacting with the resins. Precipitation preferentially occurs from those asphaltenes not being interacted as they are relatively less stable. Net cancellation of all resins remains untouched and no resins are freed as a function of the precipitation for oil C1. The foundational impact of polarity on absorption characteristics provides the potential to investigate the efficacy of microwave introduction specific to each fractionation. Experimental results from dielectric property measurements showed that the polar fractions of the crude oil, resins and asphaltenes, heavily influence the effectiveness of microwave heating. For the first time, the contribution of individual SARA fractionations to microwave efficiency was investigated.
Abstract SAGD is an energy-intensive process with large amount of greenhouse gas (GHG) emissions and required water treatment. One option to reduce emissions and water is to use electromagnetic (EM) heating in either the induction (medium frequency) or radio frequency (RF) ranges. Since the early 1970s, research into the use of RF energy to effectively heat heavy oil reservoirs has led to incremental technology advancements. Since 2009, the Effective Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH™, pronounced "easy") consortium suggested a process named similarly that dielectric heating of oil sand is combined with the injection of a solvent such as propane or butane to reduce bitumen viscosity. In January 2012, the mine face test was declared a success and confirmed the ability to generate, propagate, and distribute electromagnetic heat in an oil sand formation. Phase II of ESEIEH™ exploring scaled pilot tests with horizontal antenna in Suncor’s Dover facility is under developing. To distribute electromagnetic heating into the reservoir creation of desiccated zone and its controlled growth is a key. Since the reservoir is an electrically lossy environment, the growth of desiccated zone as a lossless medium helps the electromagnetic fields to propagate deeper into the formation and associated heating is also further developed within the reservoir. The water will continue to vaporize and move away from the "flashed or desiccated zone" at a rate which diminishes with time. Eventually it reaches the equilibrium condition that it cannot grow with given delivered RF power from the radiating antenna. In this study, the desiccated zone extension at its equilibrium is calculated on the basis of this concept to prevent the zone from collapsing. In this process, water should vaporize and leaks into reservoir to create the flow rate normal to the desiccated zone surface that pushes the water back and grow the zone. Another highlight on this study is to provide the solution for RF-heating avoiding the Lambert’s law or plane-wave assumption. Lambert’s law is (only) accurate and valid in guided-microwave structures or when the EM radiating source is far from the receiving load (relative to the wavelength), such as in optical regime or in telecommunication applications. Although, for heating applications, the maximum energy dissipation of RF waves takes place in the near-field region and not in the far-field region, hence, Lambert’s law does not give a correct solution in these cases. As a result of this study minimum required power is a function of reservoir mobility or in-situ water relative permeability. If efficiency of antenna is not high enough and reservoir mobility is greater than 10 then the RF power transmission system could not deliver enough energy to grow the desiccated zone.