Full-sealing and Cementing Technology of Long Open-hole Oil and Gas Reservoirs in Well X7 of East China Sea

According to the requirements of industry standards and specifications, in order to prevent a production-well annular pressure increasing of poor cementing quality, single-stage cementing should be used for production casing cementing in development wells. The vertical depth of reservoirs in the under member of Huagang Formation and Pinghu Formation in Xihu Sag is deep.Therefore, the technical difficulty of full-sealing and cementing of long open-hole section of Well X7 is difficult, the organization of tool materials and on-site construction procedures are cumbersome, and also affected by the following factors: oil film and mud cake of oil-based drilling fluid is difficult to be removed completely, and the performance requirements of flushing fluid and pre-fluid are high. The pressure system of open hole section is complex, and the pressure stability of cement slurry system and cement slurry column is required to prevent channeling, so the loss of weight of cement gelation leads to the decrease of static hydraulic pressure of cement, which is easy to occur gas channeling. The requirements for leakage prevention are high, and the weak layers such as the upper member of Longjing Formation or Pinghu Formation coal seam are prone to complex lost circulation. Affected by many factors such as well structure and casing eccentricity, it is difficult to improve the cementing displacement efficiency. Therefore, this well adopts six core construction control technologies: optimization of cement type, flushing design, annular static and dynamic pressure calculation, displacement rheological parameter simulation and intermediate simulation. In terms of production and operation, we have carefully organized preparations, formulated standardized cementing procedures emergency control measures, and finally achieved excellent cementing quality.