Reservoir Simulation of H2S Production During a SAGD Process Using a New Sulfur-Based-Compositional Kinetic Model

Abstract

Nowadays steam injection is commonly used as a thermal EOR method due to its efficiency for recovering hydrocarbons from heavy oils and bitumen. Reservoir models simulating this process describe the thermal effect of the steam injection, but generally neglect the chemical reactions induced by the steam injection. These reactions are called aquathermolysis and have been previously investigated through laboratory experiments. Based on these experimental results, this paper proposes a new compositional kinetic model to reproduce these reactions in the context of reservoir modeling. In particular the proposed reactions model accounts for the formation of the highly toxic and corrosive acid gas H 2 S in the presence of sulfur-rich heavy oil and predicts the modification of the oil SARA composition versus time that results from the aquathermolysis reactions. The overall objective of this paper is to understand the aquathermolysis reactions in reservoir undergoing steam injections and to provide the Oil companies with a numerical model for reservoir simulators that forecasts H 2 S production risks.The new Sulfur-Based-Compositional Kinetic Model is firstly presented and then validated in the context of laboratory-scale experiments. Its H 2 S and SARA composition predictions are based on a new simplified reactive scheme of 5 reactions coupled to a compositional and thermal reservoir simulation with no mass transfer (0D). Finally the thermo-kinetic modeling is coupled with a 2D reservoir simulation of a SAGD process for a generic Athabasca oil sand. The H 2 S to SARA (bitumen) production ratio against time computed by the reservoir simulation is found to be consistent with data from a SAGD process in Athabasca, which validates the modeling approach followed.

Comparison of Traditional and Sequential Approaches for Estimation of Kinetic Parameters of Heavy Oil Upgrading

“…Energy & Fuels crude oil. 28 Moreover, using this scheme, the production of H 2 S from saturates showed the lowest values among the SARA fractions, corroborating the aforementioned. The reaction rate coefficients for the production of H 2 and CO 2 exhibited higher values than those for the formation of CH 4 and HMWG for all SARA fraction conversions employing the reaction scheme of 29 pathways.…”

“…The proposed reaction network must describe the conversion of all lumps involved using the lowest reaction pathways without neglecting any important reaction. This is the reason why the proposal of a reaction scheme is a crucial step during the kinetic modeling. , Concerning the heavy crude oil upgrading at steam injection conditions (aquathermolysis), several kinetic models have been reported. − The reaction schemes are based on different numbers of lumps, which consist of simple networks using general components such as heavy oil or bitumen and gases such as CO 2 and H 2 S, and those that consider SARA fractions and gases such as CH 4 , H 2 , CO, CO 2 , and H 2 S, and high molecular weight gases (ethane, propane, n -butane, and their isomers).…”

Experimental Measurements of Bitumen–Water Aquathermolysis during a Steam-Injection Process

“…Several thermal reactive reservoir models have been proposed for predicting various gas productions in the SAGD process. ,,,,, The main reaction for H 2 S generation is described by the following equation: The following first-order reaction rates were proposed as follows: In general, the reaction rate constant is expressed according to the Arrhenius relationship given by where A is the frequency factor (day –1 ) and E is the activation energy (J/mol). Once the experimental data for the aquathermolysis tests are available, through gas concentrations at different times and temperatures, the activation energy and frequency factor were estimated by the following equations: where T is in kelvin and k is in day –1 .…”

Numerical simulation of solvent and water assisted electrical heating of oil sands including aquathermolysis and thermal cracking reactions

“…Using this model, they were able to predict H 2 S and CO 2 production rates comparable to those reported at field scale. Ayache et al and Barroux et al presented a sulfur‐based compositional kinetic model validated with experimental measurements. In their model the bitumen composition was defined based on SARA fractions in which its composition along with H 2 S are predicted by five simplified reactions incorporated into compositional and thermal reservoir simulations.…”