Simulation of Gas Production in SAGD

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn a previous paper, a general theory for gas production during Steam-Assisted Gravity Drainage (SAGD) has been presented 1 . The main gases formed during "aquathermolysis" reactions, carbon dioxide and hydrogen sulphide, tend to be produced primarily via the produced water.The present paper reports a numerical analysis of the theory, and provides the results of a first simulation that describe the gas production history during SAGD. The numerical analysis includes hydrogen sulphide, carbon dioxide, and methane solution gas.Gases were included in the numerical analysis by using Kvalues derived from new theory. This theory accounts for the asymptotic behaviour of gases in solution as the critical point of water is approached.Simulation results corroborate the initial simple analysis, and agree with field observation. Minor differences are discussed.

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

“…In the process of solvent and water assisted electrical heating high temperatures are expected to develop in the vicinity of the heaters. Gas generation as a result of aquathermolysis reactions and exsolution of dissolved gases in bitumen are known to negatively impact the performance of SAGD. It is believed that the accumulation of generated gases at the top of the vapor chamber form a heat transfer barrier leading to less efficient heat transfer and thus lower rate of oil recovery.…”

“…As compared to SAGD, in the proposed process of solvent and water assisted electrical heating, the formation around the heaters is exposed to temperatures in the range of 250 to 400°C . As noted, at such a high‐temperature range the bitumen is disposed to both aquathermolysis and thermal cracking reactions leading to formation of larger volume of gaseous species such a methane, hydrogen, hydrogen sulphide, and carbon dioxide . Generation of gas phase is known to negatively impact the heat transfer to the formation .…”

“…As noted, at such a high‐temperature range the bitumen is disposed to both aquathermolysis and thermal cracking reactions leading to formation of larger volume of gaseous species such a methane, hydrogen, hydrogen sulphide, and carbon dioxide . Generation of gas phase is known to negatively impact the heat transfer to the formation . The thermal cracking of bitumen can also lead to formation of coke at higher temperatures, which may impact the process performance .…”

“…There are a few studies that consider reactive nature of steam assisted gravity drainage in thermal numerical simulations. Gas generation from oil sands is often modeled using a solubility concept . In this approach the aquathermolysis reactions are not included and instead CO 2 and H 2 S were sourced in formation water and bitumen and exsolved throughout the thermal recovery process .…”

“…Gas generation from oil sands is often modeled using a solubility concept . In this approach the aquathermolysis reactions are not included and instead CO 2 and H 2 S were sourced in formation water and bitumen and exsolved throughout the thermal recovery process . In these studies, the importance of gas generation on performance of SAGD was highlighted and it was found that inclusion of gas generation slowed the recovery process …”