超深井抗盐高密度固井水泥浆技术

塔里木油田克深井区超深井固井存在井下盐膏层发育、窄间隙、高压、高温、大温差等固井技术难题，固井质量无法保证。为解决固井难题，完善了井眼准备通井技术，修正了刚度比计算公式，控制套管下放设计，通过室内实验开展加重材料的优选及合理配比、优选抗盐抗高温添加剂体系、采取针对性技术措施提高水泥石抗高温强度衰退性能，研究出了超高密度抗盐抗高温防气窜水泥浆体系，并对其进行性能评价。结果表明，该水泥浆体系流动度为18～22 cm，水泥浆上下密度差为0.03 g/cm3，其具有流动性能良好、稳定性较好、防窜性能良好、早期强度高、长期强度无衰退等优点，形成了克深井区超深井盐膏层尾管固井技术。该固井技术在现场应用5井次，测声幅固井质量良好。克深井区超深井窄间隙盐膏层尾管固井技术，不但可以解决该区块固井难题，还封固了高压盐水层，保障了该区块的安全、高效开发。 

Study on Salt-Resistant High Density Cement Slurry Technology for Ultra-Deep Wells

Cementing of ultra-deep wells in the Keshen block in Tarim Basin is faced with many downhole problems such as salt and gypsum formation to be cemented, narrow clearance between casing string and borehole walls, high pressure, high temperature and big temperature difference etc., and poor quality of well cementing job is frequently seen in this area. Several measures have been taken to solve the problems encountered in well cementing. First, the borehole to be cemented was well prepared by engineered wiper trip, the formula for calculating the stiffness ratio was revised and the running of casing string was well controlled. Second, Laboratory experiment was conducted in selecting weighting agents and cement additives that are resistant to salt contamination and high temperature. Third, specific techniques were adopted to improve the resistance to high temperature and strength decline of set cement. Based on the experiment, an ultra-high density cement slurry was developed. Laboratory evaluation showed that this cement slurry has a fluidity of 18-22 cm. The difference of density between the top and the bottom of the cement slurry is 0.03 g/cm3. It has many advantages such as good flowability, high stability, good gas-channeling prevention capacity, high early strength and no long-term strength decline. The cementing technology based on this cement slurry and measures of using it formed the base of high quality well cementing job in Keshen block where ultra-deep wells were drilled through salt and gypsum formations. Five well times of field application gave high quality cementing job as indicated by sonic logging. The technology for cementing ultra-deep well penetrating salt/gypsum formations and with narrow clearance between liner string and borehole walls not only helped solve the difficulties encountered in well cementing, but also helped cement the high-pressure saltwater zones, ensuring the safe and efficient development of the Keshen block.