The Influence of Salt Concentration in Injected Water on Low-Frequency Electrical-Heating-Assisted Bitumen Recovery

Abstract

Steam injection is often not a good alternative for oil recovery from shallow bitumen reservoirs. For instance, the thin caprock creates the danger of steam breakthrough. For deeper reservoirs, the heat losses from injection wells may be prohibitive. A technology that may be better suited is oil recovery aided by low-frequency electrical heating of the reservoir. This technology, well known for environmental remedial applications, has been field tried recently, yielding promising results. The process uses electric conductivity of connate water to propagate an alternating current between electrodes, inducing the Joule heating of the reservoir. An associated problem is the appearance of hot spots around the electrodes that may be relieved by water circulation. However, the water circulation may have a significant effect on the heating process because the electric conductivity of the circulated water depends on its salt content. To find out the influence of salt concentration on process efficiency, we have studied the process of saltwater recirculation around an electrode using numerical simulation. The physical properties and operational data for Athabasca bitumen have been collected from the literature. The model built with Computer Modelling Group's STARS simulator and tested first with available analytical solutions has been validated, and the proper choice of the underlying grid and numerical tuning parameters has been verified. The process was also simulated at field scale for a common pattern of electrodes and production wells. The salt penetrated into the reservoir, far beyond the major water-circulation zone around the electrodes. This process increases the electric conductivity in a large region between electrodes, which improves the heating of the reservoir. The single-electrode simulation studies using different tools yielded similar results for a simple problem. More-complex (and more-realistic) field-scale simulations show that adding salt enhances the oil production. In practice, an upper concentration limit may be given by corrosion problems at the electrodes. The reservoir simulation of bitumen recovery assisted by low-frequency heating is a challenging multiphysics problem. The understanding of the influence of salt concentration on the circulated water provided by this work is an important key in process-design considerations.

Active control of electro-visco-fingering in Hele-Shaw cells using Maxwell stress

“…Due to the similarity of the governing equations in our method to those in porous media, the finding of active control of EVF in the Hele-Shaw cell may also be applicable to porous media. In particular, many statuses ( Bera and Babadagli, 2015 ; Bogdanov et al., 2011 ) of electro-heating have been used for enhanced oil recovery in practical applications. By applying similar electric fields to applications of water displacing oil, it can suppress the oil/water fingering, thus making enhanced oil recovery possible by EVF.…”

Development and Application of Electrical-Joule-Heating Simulator for Heavy-Oil Reservoirs

“…To solve Eq. 5 numerically, we consider only the latent-heat term explicitly and the other terms are solved implicitly (Delshad et al 1996;Lashgari et al 2014aLashgari et al , 2014b. Because the UTCHEM simulator is an implicit-pressure/explicit-concentration simulator, first pressure is solved at a new time level and then mass-balance equations are solved.…”

Evaluation of Induced Thermal Pressurization in Clearwater Shale Caprock in Electromagnetic Steam-Assisted Gravity-Drainage Projects

“…Recovery can be improved through thermal, solvent-injection, electrical, and EM methods. EM heating for in-situ production of bitumen reservoirs can be divided into three different groups: low-frequency heating (also called electrical heating-two main types are ohmic and resistive heating), medium-frequency heating (i.e., inductive heating), and high-frequency heating [i.e., radio frequency (RF) and microwave (MW) heating] (Bogdanov et al 2011;Wacker et al 2011). Electrical heating with low-frequency alternating current (AC) [either 50 or 60 Hz, the urban and commercial power frequency; lower frequencies, such as 0.1 Hz, have also been applied to the electrodes in some cases (Vermeulen and Chute 1983)] for the recovery of bitumen has been studied since the early 1970s (Chute et al 1978;Vermeulen et al 1979Vermeulen et al , 1988Vermeulen and Chute 1983;Hiebert et al 1986;Vermeulen 2000, 2007;Vermeulen and McGee 2000).…”