The Chao-601 is a typical low-permeability naturally fractured reservoir of Daqing. Without a primary depletion, the secondary water flood was employed at the beginning of the development. Because of both the complexity of fracture distribution and relatively high oil viscosity, the water flooding could not meet the demand of stable output; the water broke through only a few years after injection. The predicted waterflooding recovery is only 13.4%. In order to improve the recovery, the investigations of steam injection in the Chao-601 field were performed. Correspondingly, a pilot test was conducted in the 119-52.

By combining plenty of geological study and multidisciplinary investigation, a simulation model describing pilot area was established. The simulation study focused on the flow characteristics of injected steam at critical condition and the effects of fractures on sweep efficiency. Furthermore, the injection system was optimized on the basis of the recognition of steam flow behavior. Important factors included the selection of well pattern, well spacing, and injection rate. Based on the optimization of injection system, the pilot test carried out in the 119-52 block.

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