Abstract

Electrical heating for heavy-oil recovery is not a new idea but commercialization and wider application of this technique require detailed analyses for determination of optimal application conditions. In this study, applicability of electrical heating for heavy-oil recovery from two heavy-oil fields in Turkey (Bati Raman and Camurlu) was tested experimentally and numerically. The physical and chemical properties of the oil samples for the two fields were compiled and measured. Then, core samples were exposed to electrical heating and oil recovery performances by the retort technique were determined for different conditions. Experiments with and without using iron powder were analyzed and in-situ viscosity reduction during the heating process was determined through a history matching process using the simulation of the laboratory experiments. Experimentally obtained oil recovery and temperature distributions were used in this history matching exercise. Iron powder addition to oil samples causes a decrease in the polar components of oil and the viscosity of oil can strongly be influenced by the magnetic fields created by iron powders. Therefore, three different iron powder types at three different doses were tested to observe their impact on oil recovery. Experimental observations showed that viscosity reductions were accomplished as 88% and 63% for Bati Raman and Camurlu crude oils, respectively, after 0.5% Fe addition, which was determined as the optimum type and dose for both crude oil samples. Different parameters (thermal diffusion coefficients, oil viscosity, and relative permeabilities) that are needed in numerical modeling as data were determined through experimentally validated numerical modeling study. Furthermore, field scale recovery was tested numerically using the parameters obtained from laboratory scale experimental and numerical modeling results. The power of the system, operation period and the number of heaters were optimized. Economic evaluation done using the field scale numerical modeling study showed that the production of one barrel petroleum costs about 5 USD and at the end of 70 days, 320 barrels petroleum can be produced. When 0.5% Fe is added, oil production increased to 440 barrels for the same operational time period.

Introduction

Crude oils whose API gravity smaller than 20 are called heavy oil (Conaway, 1999). The key to produce oil from these resources is to reduce oil viscosity, and that is best accomplished by heating these resources which can be achieved by thermal methods; i.e., hot-fluid injection, in-situ combustion and thermal stimulation (Farouq Ali, 2003; Prats, 1982). Apart from the common thermal methods, electromagnetic heating and electrical heating can also be considered as alternative thermal methods. While steam-based methods have been more successful economically and technically than others, alternative heating methods were found uneconomical for heavy-oil recovery due to the high operating costs in the past (Thomas, 2007). Because of recent increase in oil prices, electrical heating technique could be considered as a commercial method (Campbell and Laherrere, 1998).

Electrical heating tools and their applications can be divided into three different categories based on frequency of electrical current used by the tool (Sahni and Kumar, 2000). (1) Low frequency currents are used in Resistive/Ohmic heating and (2) High frequency currents are used in Microwave heating methods. (3) The Induction tools have the ability to use a wide range of low to medium frequency currents depending on heat requirements and desired temperature. These methods are applied in the field by using a downhole magnetron or heater (Prats, 1982).

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