Formation of stable emulsions under in-situ combustion conditions: An assessment of the injected gas - crude oil - water - rock interplay in Quifa oilfield, Los Llanos Basin, Colombia

Operated over a 32-month period from November 2011 to July 2014, Pacific E&P implemented the first in-situ combustion (ISC) pilot test in Quifa Field, Los Llanos Basin, Colombia. From this experience, valuable information about the design, construction, fluid properties and management of the ISC project was gained. As any project of its kind, the one carried out in Quifa Field had to face some production problems related to the formation of complex emulsified fluids, fine migration, and hydrogen sulfide production. In this paper, we discuss how Quifa crude oil, water, and rock minerals reacted each other and with the injected, oxygen-rich gas to produce extremely complex emulsified fluids. We tackle the discussion by combining geochemical, chemical and physical information to explain the occurrence of such complex fluids. The nature of organic matter, biodegradation level, and chemical composition of Quifa crude oil, as well as the reservoir rock lithology and the chemical composition of the produced crude oil and water were evaluated through a multidisciplinary and systematic analytical approach. Results were integrated in order to identify the factors and conditions that promoted the formation of such complex fluids. The purpose is to lay the foundations for future developments of laboratory approaches intended to provide information about the likelihood of a crude oil to form complex emulsified fluids under ISC conditions. Such information, in combination with the one provided by combustion tube tests, would be useful to the design, construction, and management of any for-coming ISC project.