A COMPARATIVE STUDY OF SURFACE AND DOWNHOLE HEAVY OIL UPGRADING PROCESSES: CASE STUDY OF THE THAI-CAPRI PROCESS

Crude oil is currently a primary source of transportation fuels globally. The continuous decline of light oil reserves has shifted attention to large deposits of untapped heavy oil and bitumen resources. These resources are dense and characterised by high viscosity, high asphaltenes and heteroatom (e.g., S, N, V, Ni, Fe, etc.) content, high cost of production, and low American Petroleum Institute (API) gravity. Therefore, they have low market value, which hinders their exploitation. In this regard, heavy oil and bitumen are produced by chemical or thermal enhanced oil recovery method and subsequently surface upgraded by coker processes to produce synthetic light crude oil that meet refinery feedstock specifications. Surface upgrading however incurs high capital cost, environmental impact due to emissions and is energy intensive. Nonetheless, it will be less capital intensive and environmentally friendly if downhole upgrading could be achieved during the extraction process. In this view, the CAtalytic upgrading PRocess In-situ (CAPRI) incorporated with Toe-to-Heel Air Injection (THAI) for heavy oil/bitumen recovery and upgrading was developed in 1998. This technology offers 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 cost effective and less environmental footprint compared to surface upgrading. Laboratory-scale results have shown that about 2-7º API gravity increase, 80% viscosity reduction, and 40% conversion of molecules with boiling-point (> 343ºC) can be achieved by incorporating downhole catalytic upgrading.