Optimization of the Operating Envelope of a Hot-Solvent Injection Process for Bitumen Recovery

Abstract

Summary Over the past two decades, there have been considerable efforts in the industry evaluating the use of pure solvents or solvent-assisted processes for the development of oil sands reservoirs in Canada. Replacement of conventional steam-based recovery with solvents can minimize the energy intensity of bitumen recovery and reduce the environmental footprint of the operation. Moreover, solvent-based processes can reduce the capital cost of handling large volumes of water and minimize water usage. In-situ heating techniques were also studied as an alternative means of delivering energy into the oil reservoirs while reducing the cost of surface heating facilities. One of the available in-situ heating options is electric resistive heaters (ERHs) deployed in the horizontal wells. This study examines many different aspects of bitumen recovery and process optimization by injection of superheated solvents along with the application of ERHs. New economic metrics were introduced to optimize the subsurface process performance. The study revealed that while ERH could help vaporize the injected solvents in the injector well, the induced solvent reflux subject to ERH installation in producer wells is a subeconomic strategy. Therefore, after the establishment of the initial communication between the well pairs, the producer heater is recommended to be turned off. Preheating modeling showed that the producer heater power rating could be ~1.3 kW/m. The process was optimized for pure butane and propane injection processes. The operating pressure range was found to be 500–800 kPa for pure butane and 1700–2300 kPa for pure propane in the reservoir of interest. The injector heater was set to deliver solvent at 250°C into the reservoir during the process, requiring ~1.2 kW/m power for butane and ~0.8 kW/m for propane vaporization. Finally, the requirement of water coinjection, well spacing, and uncertainty to reservoir attributes were also studied.