Technology and Application of Multistage Compound Deep Profile Control and Flooding in Ansai Extra-low Permeability Reservoir

Being the earliest extra-low permeability 100 million ton integrated oilfield developed onshore in China, the uneven contradiction of reservoir water flooding becomes prominent. The development effect worsens in the Ansai oilfield with the development time extension. To explore the technical direction of enhancing oil recovery in the encrypting area of the extra-low permeability reservoir, the research and the test of multistage composite deep flooding technology were carried out in the Wangyao encrypting area of a typical block of the Ansai oilfield. A plugging agent with high strength and flexibility was used to seal cracks and large-scale dominant channels. Micro-nano polymer particles were designed to drive oil in the water-porosity area. The multistage compound deep profile control and flooding technology of “the combination of high strength flexible and elastic plugging agent plugging fractures and micro-nano polymer particles to drive oil” have been formed generally. The technique has been applied in 23 well groups in Wangyao well pattern-filling area. The average injection pressure of a single well is 0.17 MPa/1000 m3, far lower than the level of 1.1 MPa/1000 m3 in conventional profile control, which provided favorable conditions for deep migration of flood control agent and deep production of the reservoir. After deep profile control and flooding, the water cut rise rate in the test area was obviously controlled, the natural decline rate decreased from 11.7% to 5.9%, and the water cut rise rate decreased from 2.9 to 1.8. The reservoir plane water drive was improved, the profile produced degree was increased, and the development situation improved, which indicates that multistage compound deep profile control and flooding technology shows good technical adaptability in Ansai extra-low permeability reservoir.