Experimental Measurements and Numerical Simulation of H2S Generation during Cyclic Steam Stimulation Process of Offshore Heavy Oil from Bohai Bay, China

Abstract

Cyclic steam stimulation (CSS) is successfully applied to increase heavy oil recovery in heavy oil reservoirs in Bohai Bay, China. However, during the CSS processes, hydrogen sulfide (H2S) was detected in some heavy oil reservoirs. The existing literature mainly focused on the H2S generation of onshore heavy oil. There is no concrete experimental data available, especially about the level of H2S generation during CSS of offshore heavy oil. In addition, there is still a lack of effective reaction kinetic models and numerical simulation methods to simulate H2S generation during the CSS of offshore heavy oil. Therefore, this paper presents a case study from Bohai Bay, China. First, the laboratory aquathermolysis tests were conducted to simulate the gases that are produced during the CSS processes of heavy oil. The effects of the reaction temperature and time on the H2S generation were studied. Then, a one-dimensional CSS experiment was performed to predict H2S generation under reservoir conditions. A kinetic model for the prediction of H2S generation during the CSS of heavy oil was presented. The developed model was calibrated with the experimental data of the one-dimensional CSS experiment at a temperature of 300 °C. Finally, a reservoir model was developed to predict H2S generation and investigate the effects of soaking time, steam quality, and steam injection volume on H2S generation during CSS processes. The results show that the H2S concentration increased from 0.77 ppm in the first cycle to 1.94 ppm in the eighth cycle during the one-dimensional CSS experiment. The average absolute error between the measured and simulated H2S production was 12.46%, indicating that the developed model can accurately predict H2S production. The H2S production increase with soaking time, steam quality, and steam injection volume due to the strengthened aquathermolysis reaction. Based on the reservoir simulation, the H2S production was predicted in the range of 228 m3 to 2895 m3 within the parameters of this study.

New Trends for Hydrogen Sulfide Scavenging Using Natural Compounds as Biogenic Amines

“…Equations – show that during the aquathermolysis reaction, the C–S bond of the S-containing organic molecule of heavy oil ruptured, resulting in H 2 S, CO 2 , and H 2 in the gas products. ,, In all systems, there is a higher production of CO 2 compared with the light compounds produced. This CO 2 may be produced by different paths, such as the decarboxylation of carboxylic derivatives or the water gas shift reaction (WGSR): CO + H 2 normalO ↔ normalC O 2 + H 2 …”

“…Aquathermolysis is the group of chemical reactions between high-temperature steam and at least some compounds of a mixture of heavy hydrocarbons. ,− The aquathermolysis reactions are shown as follows: organosulfur → aquathermolysis alcohol + mercaptan + normalH 2 S alcohol → aquathermolysis aldehydes aldehydes → aquathermolysis CO + hydrocarbon CO + steam → WGSR C normalO 2 + H 2 H 2 + organosulfur + mercaptan → normalh ydrodesulfurization normalH 2 S …”

“…Aquathermolysis is the group of chemical reactions between high-temperature steam and at least some compounds of a mixture of heavy hydrocarbons. 2 , 7 − 9 The aquathermolysis reactions are shown as follows: …”

New Approach to Simulate Long-Term In Situ Aquathermolysis Reaction Combining Noncatalytic and Catalytic Kinetic Models

“…During this period, the well is closed and the conditions inside the reservoir are assumed to be constant so that the chemical reactions proceed. Usually, the soaking time ranges from 5 to 14 days. ,− In this work, a soaking time of 14 days (336 h) was considered. The kinetic modeling was done only for the soaking period; that is, the reaction during injection and production periods is neglected.…”

“…An important aspect to develop a simulation model is the kinetic model that should properly represent the reactions that are carried out at in situ conditions. ,, Various kinetic models have been reported in the literature for heavy oil upgrading at steam injection conditions. ,,,− General reaction schemes for the conversion of heavy oil or bitumen into different pseudocomponents and the reactions between them have been considered. Some kinetic models have been used for numerical simulation of steam injection during the in situ upgrading of heavy oil, focusing only on the production of gases, such as H 2 S or CO 2 , and not on all pseudocomponents involved in the reaction. ,,− Some of them use a reaction scheme based on different pseudocomponents, but only the liquid phase is studied in the numerical simulation . More detailed kinetic models consider the pseudocomponents in liquid and gas phases. ,,,, The kinetic approaches have been developed for noncatalytic or catalytic in situ upgrading and used individually for numerical well simulation.…”