| abstract |
1463444 Oil recovery SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV 13 June 1975 25359/75 Heading E1F Oil having a viscosity greater than 100 cps is recovered from a formation comprising permeable blocks surrounded by a natural fracture network by (a) displacing oil from the fracture network in a region of the formation by injecting fluid into the region, (b) circulating hot aqueous fluid through the fracture network in the region to increase the temperature of the blocks in that region, (c) recovering oil during the previous steps (a) and (b), (d) stopping the circulation of hot aqueous fluid and replacing this fluid in the fracture network by a gas under pressure, (e) allowing drainage of oil from the pore space of the blocks in the region into the gas containing fractures, and (f) collecting and recovering drained oil from the lower part of the fractures in the region. The fluid injected in step (a) may be gas, steam, or water having a higher or lower temperature than the original temperature of the formation. The hot aqueous fluid circulated in step (b) may be water having a temperature higher than the original temperature of the formation, steam, or a mixture thereof. The gas under pressure in step (d) may be steam, air or natural gas that is kept stagnant in the fracture network in the region during the step (e). Steam may be added to the gas containing fractures during step (e) to compensate for heat losses in the region. |