Heavy-oil reservoirs with extremely strong water sensitivity in the Shengli oilfield are mainly distributed in the Jinjia oilfield and their reserves amount to more than 20 million tons. In addition, the thermal recovery effect only by steam injection seems poor and it is difficult to effectively produce these reserves because the water sensitivity index for this kind of reservoirs exceeds 0.9. In view of the above contradiction, a thermal compound chemical method research was carried out, in which real cores from the Jinjia oilfield were used to evaluate different displacement manners based on thermal compound chemical flooding, such as the vapor+high-temperature antiswelling agent, steam+high-performance oil displacement agent, and steam+high-performance oil displacement agent+high-temperature condensation agent. Composition changes of clay minerals, clay distributions in pore throats and radius distributions of pore throats were measured by means of X diffraction, scanning electron microscope, cast thin section and mercury-injection in order to explore principle mechanisms of the enhanced oil recovery with the thermal compound chemical method under high-temperature conditions. The results showed that the thermal compound chemical displacement manner with the steam+high-temperature oil displacement agent+high-temperature condensation agent can promote the transformation of montmorillonite to illite and the dissolution of part kaolinite at the same time, which can greatly improve pore-throat flow channels of reservoirs to form large “hot-wormholes” that remarkably increase the permeability and flooding displacement efficiency of heavy-oil reservoirs with strong water sensitivity.
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