Findings from a Solvent-Assisted SAGD Pilot at Cold Lake

Abstract

ExxonMobil and Imperial Oil Resources (Imperial) are conducting a Solvent Assisted - Steam Assisted Gravity Drainage (SA-SAGD) experimental pilot at Cold Lake in the Clearwater formation where up to 20% by volume of hydrocarbon solvent (diluent) has been injected along with dry steam in a dual horizontal well SAGD configuration. Experimental work performed by the Alberta Research Council (ARC) (Nasr, 2003) and Imperial indicated that addition of solvent to steam increases bitumen rates and decreases steam-oil ratios relative to the conventional SAGD process. The main objective of this pilot has been to produce high quality field data to definitively support these experimental conclusions. The pilot scope includes two horizontal well pairs (four wells), six observation wells, associated steam and diluent injection facilities, artificial lift, as well as, dedicated production measurement and testing facilities. The SA-SAGD pilot uses existing steam generation, water treatment, bitumen separation and processing facilities at Imperial's Mahkeses plant and existing steam distribution and production gathering systems. The main focus of this paper is to document the integrated approach taken to ensure that this multi-year pilot is successful and to provide information resulting from this multi-year pilot. Key surveillance products, such as, production/injection measurements, horizontal-well temperature logs, observation-well temperature and saturation logs, time-lapse 3D seismic, and the impact of a mid-pilot solvent switch will be discussed. In addition, this paper will review how these surveillance products are integrated with laboratory data and simulation efforts to improve our understanding of this process and increase confidence in go-forward predictions. Given the emerging importance of solvent-assisted thermal heavy-oil processes and the accelerated conversion of this technology from laboratory-scale to field-scale, data from a field pilot provides invaluable information in the quest to deploy this emerging in-situ recovery technology.

Analytical Modeling of the Cyclic ES-SAGD Process

“…For the cycles which consist solely of steam injection, the temperature at the interface will affect the viscosity of the oil and its drainage rate. To compute the oil rate, Equation (2) was modified using the new oil viscosity at the steam temperature as shown in Equation (17). In this expression, ν T s is the kinematic oil viscosity at the steam temperature which was used to calculate the constant B 3 and ν T inter f is the kinematic oil viscosity at the interface.…”

Semianalytical Modeling of Steam/Solvent Gravity Drainage of Heavy Oil and Bitumen: Unsteady-State Model With Curved Interface

“…At distances away from the injection point, steam starts to condense, delivering its latent heat to the surrounding rock and residual fluids left behind in the swept area. As a result, the steam mole fraction decreases with distance from the injection point, while increasing the solvent fraction in vapor phase at the same time (Dong 2012). Because of a larger temperature gradient at the edge of the steam chamber, the rate of conductive-heat transfer is high, reducing steam saturation to a lowest value and thus reducing the steam partial pressure and saturation temperature to a minimum value within the steam chamber.…”

“…1 and 2 are estimated by use of a simplified procedure proposed by Dong (2012). This procedure evaluates the equilibrium values at the interface for a binary mixture of steam and solvent by use of the saturation pressures of the pure components.…”

Liquid–Liquid Equilibrium Studies of Multicomponent Diluent/Bitumen System with Application to Solvent-Aided In Situ Bitumen Recovery

“…16 In Imperial Oil's SA-SAGD pilot at Cold Lake, where a higher percentage of solvent (∼20 vol %) was coinjected with steam, daily oil production rates increased significantly. 17 Additionally, Imperial Oil has proposed the enhanced bitumen recovery technology (EBRT), which utilizes a heated vapor extraction process with 90% light hydrocarbon solvent and 10% steam at low injection pressure, resulting in increased oil production using significantly less steam compared to SAGD and significant reduction of greenhouse gases. 12 The Cenovus solvent-driven process (SDP) pilot project at Foster Creek successfully reduced CO 2 emissions by utilizing a combination of solvent and steam.…”