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Numerical simulation of the impact of geological heterogeneity on performance and safety of THAI heavy oil production process

Ado, Muhammad Rabiu; Greaves, Malcolm; Rigby, Sean P.

Authors

Muhammad Rabiu Ado

Malcolm Greaves

SEAN RIGBY sean.rigby@nottingham.ac.uk
Professor of Chemical Engineering



Abstract

The Toe-to-Heel Air Injection (THAI) in-situ combustion process is an efficient way to extract heavy oil and bitumen. However, such reservoirs are often geologically heterogeneous. This work studied the impact of a range of different geological heterogeneities, often found in bitumen deposits, on the performance and safety of THAI. These heterogeneities included random heterogeneity, layered reservoirs, shaly reservoirs, and semi-permeable cap-rocks. A further aim was to also develop potential remedial measures, such as selective well placement. It was found that the degree of symmetry assumed for the reservoir model had a substantial impact on the predicted level of oil production. This is of particular relevance to otherwise apparently symmetrical well placement designs such as staggered line drive. While the presence of impermeable zones resulted in the decrease in the overall oxygen utilisation for shaly reservoirs, compared to simply low permeability reservoirs, there was no evidence of oxygen breakthrough due to preferential channelling into the production well. In layered reservoirs, the development of a rich oil bank during THAI operation depended upon the distribution of permeability around the horizontal producer (HP), and did not occur when there was high permeability just above the HP. It has been shown that the proper representation of the cap-rock in reservoir models for the simulation of THAI is essential in order to accurately mimic the full pattern of heat distribution into the oil zone of the reservoir, and, thence, fuel lay-down. While THAI can operate stably with a permeable cap-rock, vertical permeabilities above ∼1–3 mD led to significant loss of combustion gases from the reservoir.

Citation

Ado, M. R., Greaves, M., & Rigby, S. P. (2019). Numerical simulation of the impact of geological heterogeneity on performance and safety of THAI heavy oil production process. Journal of Petroleum Science and Engineering, 173, 1130-1148. https://doi.org/10.1016/j.petrol.2018.10.087

Journal Article Type Article
Acceptance Date Oct 24, 2018
Online Publication Date Oct 26, 2018
Publication Date 2019-02
Deposit Date Oct 29, 2018
Publicly Available Date Oct 27, 2019
Journal Journal of Petroleum Science and Engineering
Print ISSN 0920-4105
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 173
Pages 1130-1148
DOI https://doi.org/10.1016/j.petrol.2018.10.087
Keywords Bitumen; Shale inter-layer; Heterogeneity; Cap-rock; Thief-zone; THAI
Public URL https://nottingham-repository.worktribe.com/output/1202427
Publisher URL https://www.sciencedirect.com/science/article/pii/S0920410518309550