Fourth-section liner cementing technology used in the complex ultradeep well KS1

Well KS1 is a high-temperature, high-pressure and ultradeep well and it is faced with several cementing difficulties, e.g. coexistence of overflow and leakage, hole shrinkage in salt rock beds, high-pressure saline aquifer, low displacement efficiency and channeling. To solve these difficulties, a special cementing process is adopted in the fourth-section cementing of Well KS1. According to the special cementing process, the cementing process of bottom liner hanging is firstly performed. Then, the milling taper is run into the hole to dress the fourth-section milling bell mouth and tie back barrel after fifth-section drilling, fifth-section liner cementing and fifth-section intermediate completion operation (plug drilling, wall scraping and electric logging) are carried out. Finally, the fourth-section cementing of tie back casing is performed. In order to ensure the smooth implementation of the fourth-section liner cementing operation, the difficulties in the cementing operation were analyzed sufficiently on the basis of drilling complexities. Then, detailed technical measures were prepared from the aspects of drifting technology, casing running technology, slurry system, cementing displacement and cementing construction process. The logging interpretation of cementing quality shows that high-pressure saline aquifers, thief zones and sensitive zones are all plugged effectively and the target of “wearing shoes and hats” is realized, so as to create the favorable conditions for the subsequent oil/gas development and wellbore integrity. The successful cementing of Well KS1 provides the experience for the cementing operation in similar complex salt rock beds in the future.