Berna Hascakir

Field-Scale Analysis of Heavy-Oil Recovery by Electrical Heating

SummaryElectrical heating for heavy-oil recovery is not a new idea, but the commercialization and wider application of this technique require detailed analyses to determine 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 numerically. The physical and chemical properties of the oil samples for the two fields were compiled, and in-situ viscosity reduction during the heating process was measured with and with-out using iron powder. Iron powder addition to oil samples causes a decrease in the polar components (such as carboxylic and phenolic acids) of oil, and the viscosity of oil can be reduced significantly because of the magnetic fields created by iron powders. 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 at 88 and 63% for Bati Raman and Camurlu crude oils, respectively, after 0.5% iron (Fe) addition, which was determined as the optimum type and dose for both crude-oil samples. Next, field-scale recovery was tested numerically using the viscosity values obtained from the laboratory experiments and physical and chemical properties of the oil fields compiled from the literature. The power of the sys-tem, operation period, and the number of heaters were optimized. Economic evaluation performed only on the basis of the electricity cost using the field-scale numerical modeling study showed that the production of 1 bbl petroleum costs approximately USD 5, and at the end of 70 days, 320 bbl of petroleum can be produced. When 0.5% Fe is added, oil production increased to 440 bbl for the same operational time period.IntroductionCrude oils whose API gravity is 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 techni-cally than others, alternative heating methods were found to be uneconomical for heavy-oil recovery because of the high operating costs in the past (Thomas 2007). Because of recent increase in oil prices, the 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 categories on the basis of the frequency of electrical current used by the tool (Sahni et al. 2000):(1) Low-frequency currents are used in resistive/ohmic heating.(2) High-frequency currents are used in microwave heating methods.(3) 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 mag-netron or heater (Prats 1982). Heating with frequencies less than 300 kHz can be described as electrical-resistance heating (ERH) (Maggard and Wattenbarger 1991). This mode of heating for petroleum recovery has been known since the late-1960s. Reservoir-simulation models (Rangel-German et al. 2004; Sierra et al. 2001) and experimental models (Newbold and Perkins 1978; Amba et al. 1964) have been used in the past to study electrical heating. Electromagnetic heating such as microwave heating for recovery of heavy oil from thin pay zones, was studied experimentally (Jha and Chakma 1999; Acar et al. 2007). In order to enhance the electromagnetic heating efficiency, use of receptors such as activated carbon, iron oxides, and polar-ized solvents has been proposed (Jackson 2002). 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. Experimen-tal studies were conducted to study the efficiency of the method. In addition, to reduce the viscosity of oil, different types of iron powders were used. Experimental results coupled with the data available in the literature were used to simulate the process numeri-cally at the field scale. TheoryAs an electromagnetic wave that is radiated from the electrodes into the oil-bearing formation propagates into the formation, flu-ids and other reservoir materials impede its passage by providing resistance to the flow. As a result, the intensity of the propagating wave is reduced and the energy is converted to heat. There are key differences between low- and high-frequency heating. At low frequencies, resistance heating dominates compared to dielectric heating that dominates at higher frequencies. Heat transfer from an electromagnetic-wave source to a porous medium can be described by the energy equation. Evolution of temperature as a result of electrical energy can then be obtained by the heat equation, with the following modification:

Microwave Assisted Gravity Drainage of Heavy Oils

Conventional EOR methods like steam-injection are usually not cost effective for deep wells and wells producing from thin pay zones, due to excessive heat loss to the overburden. For such wells minimizing heat losses can be achieved by using microwave heating assisted gravity drainage. In this study, the feasibility of this method was investigated. Heavy oil samples from conceptual reservoirs (Bati Raman (9.5 API), Garzan (12 API) and Camurlu (18 API)) in south east Turkey were used. Using a novel graphite core holder packed with crushed limestone premixed with crude oil and water effects of operational parameters like heating time and waiting period as well as rock and fluid properties like porosity, permeability, wettability, salinity, and initial water saturation were studied.

Design of flow control devices in steam-assisted gravity drainage (SAGD) completion

AbstractCommercialization of the steam-assisted gravity drainage (SAGD) process has made recovery of heavy oil/bitumen possible in a number of reservoirs hindered by hydrocarbon immobility. However, the economics of this process are highly sensitive to the efficiency of steam creation, delivery, and use, with a successful and unsuccessful SAGD well pair often separated by how effectively thermal inefficiencies can be mitigated in the flow profiles of steam injection and/or in emulsion recovery. To improve flow profiles, Albertan SAGD completions have experimented with the addition of flow control devices (FCDs). These completion tools have historically been used to regulate liquid inflow across long producing laterals, adding a variable pressure drop along the lateral to improve the conformance of hydrocarbon production and delay water breakthrough; within SAGD completions, FCDs find novel use to force a more even flow distribution of steam in the injector and a thermally dependent inflow profile in the producer to maximize recovery of heavy oil/bitumen. This paper provides a comprehensive overview of different FCD designs, discussing their respective methods of regulation, the fluid-adaptive behavior of “autonomous” FCDs, operational strengths and weaknesses of different commercial offerings, and suggestions on how to use existing pressure loss models for FCDs and apply them to the non-traditional application of regulating SAGD flow profiles, both for equipment sizing and estimation of pressure loss/flow rates across the device. From this work, it is proposed that use of autonomous FCDs in the production lateral are of greater value than use of flow control in the injector; however maximum benefits are achieved by coupling simple orifice-style FCDs in the injector lateral with autonomous, large flow path (non-orifice) FCDs capable of controlling steam flash events in the production well.