Pilot study on waterflooding development in multi-well fracture-cavity units of Tahe Oilfield

Ordovician reservoirs in Tahe Oilfield are carbonate fracture-cavity reservoirs. In order to control the quick natural decline caused by the shortage of reservoir energy, Tahe Oilfield explored to test waterflooding development in multi-well fracture-cavity units in 2005. According to the reservoir development characteristics, reservoir energy, and water body features, water injection was performed in different fracture-cavity units and position with different injection mode and rate. Main factors affecting injection effect were analyzed. The results prove that waterflooding effect is good when surplus oil is rich between the injection and production well, reservoir is relatively homologous, and water injection lies in the low position of fracture-cavity unit. Moderate injection should be conducted to prevent the injection water from dashing fast, with the initial injection-production ratio at 0.8～1.0.Successful test provides technological support and theoretical basis for efficient and rational development of similar reservoirs.