Heat of Combustion Analysis of Residual Hydrocarbon Following In Situ Combustion Tests
Creators: name: Kamisaki, Marta Hiromi
Publisher: name: Graduate Studies
Year: 2018
Subjects: subject: In Situ Combustion
subject: Heat of Combustion
subject: Residual Hydrocarbon
subject: 3-D Test
subject: Coke
subject: Hydrocarbon Fractions
subject: Engineering--Petroleum

description: Production of Athabasca Oil Sands has always been a challenge due to its high viscosity. To produce the subsurface oil, enhanced oil recovery (EOR) is necessary. In Situ Combustion (ISC) is an EOR technique with high recovery factor but, due to the high number of reactions occurring simultaneously during application of the method, the use of computational simulators is still a challenge. Therefore, laboratory physical simulations are necessary to evaluate the viability of ISC in a specific field. These simulations are normally conducted using core samples in one-dimensional combustion tube tests to analyze the temperature profiles, pressure drops, product gas compositions and fluid production. A new 3-D physical laboratory simulator has been developed by the In Situ Combustion Research Group at the University of Calgary. The model consists of a 3-D box to evaluate ISC as a hybrid process with steam. The advantage of the 3-D model is that it provides better visualization of the process since multiple dimensional data are obtained. Post-test core samples that exhibited a significant coke bank or wall were selected from two 3-D tests which had been previously performed using cores from Athabasca Oil Sands reservoirs. Both of the 3-D tests evaluated in this research simulated a pre-production by SAGD (Steam Assisted Gravity Drainage). The 3-D boxes were packed with two distinct oil zones: Rich Zone (with a higher oil concentration) and Lean Zone (with a lower oil concentration). Lean Zone represented the area pre-produced by SAGD. After packing, the ISC process was performed with dry air (21% oxygen) injection during 3-D Test #1 and with enriched air (95% oxygen) and super-heated steam co-injection during 3-D Test #2. This current study analyzes selected samples of the post-test residual that are associated with the coke bank or coke wall in terms of the heats of combustion of residual hydrocarbon in contact with the sand, the toluene extractable oil, its fractions (maltenes and asphaltenes), as well as the toluene insoluble coke fraction remaining on the extracted core matrix. The higher O2 concentration on the injected fluid used during 3-D Test #2 might have increased the oxidation of the hydrocarbons. As a result, the heat of combustion of coke from 3-D Test #2 was found to be lower than from Test #1 (with normal air injection). Therefore, it was not possible to obtain a generalized value for the heat of combustion of coke for Athabasca Oil Sands. Coke showed to have a lower contribution to the total heat of combustion when compared to other hydrocarbon components tested (oil, maltenes and asphaltenes). For this reason, coke appears to not be the main fraction used as fuel used during In Situ combustion process. A significant finding from this study is that the residual hydrocarbon which is visually identified as the coke bank or coke wall is a mixture of maltenes, asphaltenes and toluene insoluble coke fractions. It was also observed when measuring the heat of combustion of samples that involved residual hydrocarbon plus sand that either gelatin capsules or benzoic acid was required to achieve complete combustion of the samples.