A COMPARATIVE STUDY OF SURFACE AND DOWNHOLE HEAVY OIL UPGRADING PROCESSES: CASE STUDY OF THE THAI...

Crude oil is currently the world's principal source of transportation fuel. As light oil stocks continue to dwindle, focus has switched to massive amounts of undeveloped heavy oil and bitumen resources. These resources are dense and have a high viscosity, a high content of asphaltenes and heteroatoms (e.g., S, N, V, Ni, Fe, etc.), a high cost of production, and a low American Petroleum Institute (API) gravity. As a result, they have a low market value, which makes them difficult to exploit. In this manner, heavy oil and bitumen are extracted using chemical or thermal improved oil recovery methods and surface upgraded using coker procedures to produce synthetic light crude oil that meets refinery feedstock criteria. Surface upgrading, on the other hand, has a high capital cost, a negative environmental impact due to emissions, and is energy intensive. Nonetheless, if downhole upgrading can be accomplished during the extraction process, it will be less capital intensive and more environmentally benign. In this regard, in 1998, the CAtalytic upgrading PRocess In-situ (CAPRI) with Toe-to-Heel Air Injection (THAI) for heavy oil/bitumen recovery and upgrading was created. This technology has the advantage of using in-situ generated energy from pyrolysis and thermal-oxidation reactions activated by in-situ combustion to drive extraction, as well as in-situ catalytic upgrading to convert heavy feedstock into almost light oil, making it more cost effective and having a smaller environmental footprint than surface upgrading. Laboratory-scale data demonstrate that integrating downhole catalytic upgrading can result in a 2-7o API gravity rise, an 80% viscosity decrease, and a 40% conversion of compounds with boiling points (> 343oC).

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