Recently, the Hainan Branch of CNOOC Limited came to the news: located in the Yinggehai Basin, Ledong 10-1 gas field, in the ultra-high density of 2.20g/cm³, ultra-high temperature of 190 ℃, very narrow pressure window of 0.035g/cm³ extreme conditions, to overcome the high solid phase brought about by high pressure tailpipe hanging sitting hanging, tailpipe hanging hanging sitting and hanging and other technical difficulties, through the refinement of the operation for the first time, will be the 9.625-inch Through refined operation, the 9.625-inch tail pipe was sent to 4,761 meters for the first time, successfully realized the tail pipe hanging hydraulically, and the tools were smoothly taken off. The successful tail pipe hanging marks a major breakthrough in China's drilling technology in the field of ultra-high-temperature, high-pressure and very narrow pressure window. This achievement not only shows China's technical strength in the field of energy development, but also provides a solid well control barrier for safe drilling in the target layer, which is undoubtedly another milestone in the history of China's offshore oil industry.
As China's first offshore ultra-high-temperature and ultra-high-pressure gas field, the development of Ledong 10-1 gas field is unprecedentedly difficult. The gas field is buried more than 4,200 meters deep underground, the temperature of the target layer is as high as 214℃, and the pressure coefficient reaches 2.3g/cm³, which are extreme conditions that are a great challenge to the engineering technology and operators. Under the extreme working conditions of high specific gravity mud and high solid phase, it is easy for the tail pipe hanging kava to bite the casing wall unsuccessfully or slip after biting, which leads to the difficulty of tail pipe hanging sitting and hanging. All these greatly increase the difficulty of tailpipe hanging, so how to improve the success rate of tailpipe hanging in heavy mud has always been plagued by the major international oilfield operating companies.
In order to ensure the high quality of the large-size tailpipe launching, seating and offhanding operations, and to lay a solid foundation for the efficient execution of cementing operations, the project team adopted a series of coordinated management measures and optimized the tailpipe hanging design. At the management level, the project team set up a professional steering group and gathered the wisdom of top experts in the industry to refine the operation plan and formulate thorough risk response measures. At the same time, the project team upgraded the on-site management, strengthened the comprehensive ability of the on-site operation team by selecting the best and the brightest, and ensured the precise and strict implementation of each measure. In terms of tailpipe hanging design optimization, the project team upgraded the tailpipe hanging tool with high-temperature resistance, and raised the temperature rating of the tool to 190℃ in order to adapt to the extreme high-temperature environment. The sealer at the top of the tailpipe adopts V0 grade sealing technology to ensure zero bubble leakage under the high temperature and high pressure production environment, effectively preventing the occurrence of annular pressure problems. In addition, the seating of key components is filled with high-temperature and high-pressure resistant sealing grease, especially in the gap of the moving parts of the tailpipe-hanging liquid cylinder and tailpipe-hanging kawa, which greatly enhances the stability and sealing performance of the components. Through this design, it effectively prevents the solid phase in the high specific gravity slurry from being deposited around the moving parts of the tailpipe hanger, thus avoiding the sticking of the parts and significantly improving the success rate of the tailpipe hanger seating.
The successful implementation of this tail pipe hanging operation not only lays a solid foundation for the graded cementing technology of ultra-high temperature and high pressure with very narrow pressure window, but also lays a solid foundation for the effective sealing of this well section and the guarantee of wellbore integrity. This technological innovation provides a strong guarantee for the realization of long-lasting sealing and cementing of ultra-high-temperature and high-pressure production wells as well as the long-term stable production of oil and gas fields. It marks a significant improvement in the drilling and completion capability of CNOOC Hainan Branch under complex geological conditions, providing solid technical support for the efficient development of China's oil and gas resources, and is expected to become a key force in promoting China's oil and gas industry to achieve more technological breakthroughs in the field of ultra-high temperature and high pressure.
