Cementing Technology for Buried Hill Reservoirs in Block Yangshuiwu in Huabei Oilfield

Three key exploratory wells have been deployed in Huabei Oilfield to develop the buried hill reservoirs in Block Yangshuiwu in Langgu sag of Jizhong depression. The geologic conditions in the buried hill are complex. The formation pressure coefficient is 0.94-1.09. There exist multiple deep active oil and gas zones. Lost circulation has occurred frequently in this area. High geothermal gradient, slim hole, narrow annular clearance, long section of liner string to be cemented and rigorous requirements on the integrity of cement sheath. It is understood from these facts that cementing of the 127 mm liner string is highly risky, and operation safety and job quality of well cementing are difficult to guarantee. Efforts have made to deal with these difficulties:1) optimizing technology for borehole cleaning, using cyclone sub centralizer to ensure the success of casing running. 2) using computer software to simulate displacing efficiency and pressure changes at critical spots. Appropriately adjust operation parameters to ensure pressure control. 3) using tough cement slurry and flushing spacer system, designing appropriate operational parameters, ensuring the stability of cement slurry and the toughness of set cement that satisfies the requirements for SRV fracturing. Field operations on three wells show that the application of cementing technology remarkably improved the job quality of well cementing, providing technical support for well cementing in the buried hill in the Block Yangshuiwu in Huabei Oilfield.