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

Abstract

Coinjection of solvent with steam in steam-assisted gravity drainage (SAGD) has shown promising results for enhancing oil rates as well as reducing energy and water consumption. Modeling and optimizing hybrid-steam/solvent-recovery processes by use of commercial numerical simulators can be very time-consuming. Semianalytical mathematical models may be used to estimate production rates and thermal efficiency in much less time.In this study, an unsteady-state semianalytical model was developed to predict the oil-flow rate in the steam/solventassisted-recovery process. The model assumes a curved interface with transient temperature and solvent distribution in the mobile zone. It also accounts for transverse dispersion and concentrationdependent molecular diffusion for solvent distribution. The oilflow rate and interface profile are predicted at each time in an iterative fashion. The model is validated against the CMG-STARS thermal simulator as well as experimental results for hexane-aided SAGD physical-model tests. The semianalytical model was able to predict oil-production rates by use of different solvents coinjected with steam, in agreement with reported experimental data.The proposed model accounts for the complex interaction of heat and solvent solubility and diffusion as they affect mobilization and production of viscous oil. This model may be used to estimate the optimal operation parameters for the process over a range of different reservoir qualities and pressures, in a very time-efficient manner. The final outcome may lead to an efficient design of a steam/solvent-recovery process that uses less water and reduces the amount of energy and gas emissions per barrel of oil produced.

Analytical Modeling of the Cyclic ES-SAGD Process

“…The performance of an ES-SAGD process was analytically modeled by Rabiei [24] in 2017. In this study, an unsteady-state semi-analytical model was developed to calculate the oil rate in an ES-SAGD process.…”

“…In this study, an analytical model that can be used to approximate the oil production rates and the cumulative oil production in a cyclic ES-SAGD process is presented. The organization of the manuscript is as follows: The theory section will review the necessary components of the models of Butler [2] and Rabiei [24] before subsequently discussing how these two models can be combined for analyzing cyclic ES-SAGD processes. The ensuing results section will be divided into three sections.…”

“…The ensuing results section will be divided into three sections. In the first section, the performance of Butler's model [2] and Rabiei's model [24] will be evaluated. Subsequently, the cyclic ES-SAGD analytical model will be compared against the results from numerical simulations performed by Manfre Jaimes et al [29], including the performance of hexane, pentane, and butane as the solvents.…”

“…In this section, Butler's model for SAGD [2] and Rabiei's model for ES-SAGD [24] are briefly reviewed. Subsequently, the new model for cyclic ES-SAGD is presented.…”

Effects of Solvent Properties and Injection Strategies on Solvent-Enhanced Steam Flooding for Thin Heavy Oil Reservoirs with Semi-Analytical Approach

“…Rabiei Faradonbeh et al [28] also employed HIM to determine the temperature profile. Therefore, the temperature of the hot water can be expressed as:…”