Downhole gasification for improved oil recovery

A new, unique, IOR concept has been investigated for application in light oil reservoirs that have been previously water flooded, but which can be applied at any stage of oil prodn. The method operates via GSGI (gravity stabilized gas injection), but does not require the injection of displacement gas from the surface. Instead, gas is generated in situ, using a downhole (underground) gasification unit. The economics of the process, in terms of the energy required to produce a barrel of incremental oil appears to be very attractive. In addn. to addnl. oil, the process also produces hydrogen, and other inert gases. These gases can be stored in the reservoir for future use. The primary scope for applying the method appears to be in watered flooded reservoirs, or other depleted light oil reservoirs, in which the pressure has been reduced to less than 150 bar, if co-evapn. of oil and water is employed. However, if water (steam) is injected sep., then there is no restriction on reservoir pressure, within the limits of economic operation. The paper reports the first, preliminary set of results for downhole gasification. A small exptl. gasifier was developed to simulate the steam reforming of 'light naphtha' fractions, cut from light crude oils. Although designed for operation up to 800 DegC and 140 bar pressure, the continuous flow system was restricted in these trials to around 75 bar pressure. The commissioning and preliminary trials used methane gas as feedstock, in order to test if it was possible to convert methane to hydrogen and other gases at significantly higher pressures than those normally used in surface reforming plant. Methane is also a very significant component of most reservoir oils and therefore has an important influence on how much displacement gas can be produced. The initial expts. achieved a hydrogen concn. in the reformer-gasifier exit gas of nearly 60%. Further trials were also made using a reservoir gas. [on SciFinder (R)]