Date of Award

December 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Engineering

First Advisor

Dongmei Wang

Abstract

The North Slope of Alaska (ANS) contains an estimated 40 billion barrels of heavy oil in relatively shallow formations (984 to 1,969 ft / 304 to 600 m) within the Prudhoe Bay Unit (PBU), Milne Point Unit (MPU) and Kuparuk River Unit (KRU). Extracting this resource presents unique challenges, especially when hydrocarbon-bearing zones are near the permafrost. Research on tertiary recovery processes in these shallow zones is limited, with prior studies indicating minor permafrost thawing and subsidence over 30 to 40 years but lacking a numerical simulation model supported by laboratory data.This study investigates the feasibility of an enhanced oil recovery (EOR) polymer method for extracting heavy oil from these shallow reservoirs without causing significant long-term thermal impact or geomechanical subsidence in the permafrost. Geological properties derived from well logs, completion logs, and production data from a 2016 Milne Point polymer flood pilot project were used to develop a numerical model for predicting permafrost stability. Additionally, laboratory experiments in a thermal monitoring chamber measured temperature changes around a production wellbore at the permafrost base. Results from both the field-scale models and lab-scale experiments showed a gradual temperature increase around the production wellbore. The numerical models predicted minor geomechanical subsidence (<0.1%) and a modest temperature rise (~0.53°C) at a gradient of ~0.0249°C/year. The lab-scale experiments at higher flow rates showed temperature increases ranging from approximately 0.433°C to 0.46°C, corresponding to a gradient of ~0.0171°C/year. Importantly, these findings indicate that the polymer flooding process does not cause significant long-term thermal impact or geomechanical subsidence at the base of the permafrost, affirming its stability. By integrating thermal chamber data and numerical models, the study offers a comprehensive understanding of the thermal and geomechanical effects of polymer flooding on permafrost stability.

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