A Temporary Plugging Technology to Protect the Fractured Reservoir during Workover

In order to protect fractured reservoirs during workover,a new temporary fracture plugging agent was developed on the basis of research on damage mechanism of fractured reservoirs and the concept of temporary plugging at tips of fractures with special materials.This agent could keep the operating fluid from flowing into the fractures and decrease the flowing resistance of oil and gas.In laboratory test,it formed temporary plugging for 1-2 mm artificial fractures,which could be removed easily since the plugging materials just accumulated at the tips of fractures and rarely entered into the fractures.The field application in Daqing Oilfield indicated that this agent could work under a positive differential pressure up to 30 MPa and a formation temperature up to 140℃.The temporary plugging cut off the operating fluid invading the reservoir,so that damage was avoided,and the plugging could be easily removed by negative pressure.After workover,the production rate of the gas wells recovered by nearly 100%.This suggested the feasibility to adopt temporary fracture plugging in workover to protect the fractured reservoir.Nevertheless,further study should be made on such technology,to prevent the production decline of gas well after the workover operation.