Great breakthrough has been made in heavy oil EOR mechanism under water injection at different state. New findings from both experimental and theoretical studies provide strong support for the broad application prospect of steam in heavy oil EOR. In this paper, a series of studies are carried out on productivity of a horizontal well with several vertical steam injectors during the steam-assisted-gravity-drainage (SAGD) process.

In this paper, a novel topic is discussed on the effect of steam state on oil productivity during the SAGD process. The injection wells are three parallel vertical wells and the production well is a horizontal well. The numerical method is adopted to reveal the physical aspect mechanisms. Some meaningful conclusions are listed below.

(a) The usefulness of superheated steam in heavy oil recovery lays in its chemical reactions with heavy oil and rock minerals. The effect of physical heating on oil recovery efficiency is weak. (b) The oil production rate at the starting stage, from 0 day to 30 day, is oscillating with time due to the fact that the preheating stage is neglected. The connectivity between injectors and producer is poor without a necessary step of preheating. (c) The direction of oil recovery is from well-bottom of the injector to the well-head and then to the places between the injectors. (d) Chemical reactions may play an important role in oil recovery efficiency if the final recovery efficiency by injecting steam with higher steam quality is several order of magnitude than that by injecting steam with lower steam quality.

We carried out the pilot study on the effect of steam state on heavy oil EOR during the SAGD process with several vertical injectors. More importantly, the pilot study conducted in this paper provide the very basis for the application of superheated steam for oil companies and following academic research in the field.

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