In Situ Upgrading of Llancanelo Heavy Oil Using In Situ Combustion and a Downhole Catalyst Bed

Abstract

Abstract There are vast heavy crude oil resources worldwide that are relatively uneconomical to produce and upgrade. However, there are novel processes available that can be employed in a downhole environment to upgrade these oils, resulting in significantly less sulphur content, and lowered densities and viscosities. A process that is especially favourable for downhole implementation is the use of in situ combustion to generate reactive upgrading gases, such as CO, and possibly H2, to drive oil over a near-wellbore heated bed of catalyst. Two laboratory combustion tube tests were completed to validate this concept. The first test used conventional in situ combustion tube packing and testing techniques, while the second test employed a heated catalyst bed in the downstream region of the combustion tube. A heavy crude oil from the Llancanelo field in Argentina was used for the testing. During the first test, this oil was found to be amenable to the in situ combustion process and exhibited stable combustion performance. Passing mobilized oil and combustion gases over the catalyst bed prior to production in the second test resulted in significant upgrading of the produced oil, including substantial decreases in oil density and viscosity. It is believed that the catalyst efficiently used CO, generated at the combustion front, via the water gas shift reaction to generate H2, which then reacted with the oil to effect upgrading. However, it was found that the presence of a large amount of coke on the post-test catalyst probably indicates the need for periodic regeneration. The presence of a heated production-end catalyst zone did not significantly affect the in situ combustion performance during the second test. Introduction Although there exists a large supply of heavy crude oil throughout the world, most of these reserves lie untapped for various reasons, chief among them being the poor economics of recovering heavy oils. While these economics are beginning to change as conventional oil production declines significantly, the cost-effective production and processing of heavy oils remains a much sought after prize. The authors have previously described how in situ combustion, in combination with a near-wellbore catalyst bed, could be used for significant downhole (in situ) upgrading of heavy crude oils(1, 2). This reference also discusses the potential advantages of in situ upgrading using in situ combustion and a fixed catalyst bed, as well as providing a literature review of the subject. Greaves and Xia(3) and Xia et al.(4) have recently been looking at other variations to the catalyzed in situ combustion process. Two laboratory experimental runs were completed to test the potential of using combustion-produced gases to catalytically upgrade heavy crude oil from the Llancanelo field in Argentina. The first test used conventional in situ combustion tube packing and testing techniques, while the second test employed a heated catalyst bed in the downstream region of the combustion tube, affording the oil an opportunity to be upgraded prior to production.