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Abstract: Benefits of Insitu Upgrading Reactions on the Integrated Operations of the Orinoco Heavy Oil Fields


Recently development has been expanded at several very large heavy oil reservoirs. A notable example is the Orinoco Tar Belt. While these reservoirs have 9-11 API oil, they are deep enough, contain enough gas, and hot enough that substantial primary production is possible. However, primary production will only recover around 20% of the oil, a diluent is needed in the pipeline to the coast, and a costly upgrader is needed to produce salable crude.

Insitu thermal visbreaking reactions have been studied for several decades, but may not be important in most fields because the steam temperature is not high long enough to crack the crude. However, Orinoco reservoirs are deep enough, and are being developed with a large enough spacing for substantial volumes of the crude oil to be above 250 C at least ten years. In these circumstances, simulations suggest that 8 to 10 percent of the heaviest oil components pyrolyze, resulting in most of the produced oil having an API gravity of 25 or more, and facilitating substantially increased production of light transportable, easier to refine oil.

The calculated API gravity of the cracked produced crude oil appears high enough for it to be used as the diluent for normal primary production or to not require upgrading on the coast if all production were upgraded in situ. The simulations and supporting economic calculations suggest that a reservoir with properties like the Hamaca leases, infilled to 25 hectares, could produce almost three times as much oil as 25-hectare primary production. Much more oil could be economically produced because the oil has a higher value. This extended increased production results in very favorable returns on investment in a multi-pattern steam injection project, and reduces the investment needed to achieve production goals if only primary production were implemented. In addition, no diluent would be needed. This reduces cost by around $1 US per barrel. Additional savings would result from either a smaller upgrader or increased throughput at an existing upgrader.

Thus, the overall return on investment for reservoirs like Hamaca which need integrated production-upgrading facilities could be substantial if steam injection is implemented properly. Thus, in situ upgrading of the tar in these reservoirs is a subject that deserves further study.


AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California