金坛盐穴储气库定向井固井技术

金坛储气库二期二阶段为了提高盐岩资源利用率，实现达容达产，改变以往直井钻井方式，采用了丛式定向钻井建库模式，容易导致井径不规则，套管居中度也很难保证。另外，盐层埋深较浅，低温盐水水泥浆稳定性差、失水量不易控制、抗压强度发展慢；二开井段易发生漏失，水泥不能返至地面，给固井质量带来不利影响。笔者结合盐穴储气库对固井的要求，开展了低温高强盐水水泥浆、增黏盐水隔离液及配套固井技术研究。研究结果表明，低温高强度盐水水泥浆浆体稳定性好，抗压强度发展快，后期强度高，满足了盐穴储气库定向井水泥浆体系的需求；增黏盐水隔离液，配合定向井套管居中等技术措施，提高了在"大肚子"及不规则井段的顶替效率，预防固井施工憋堵；采用低排量顶替技术保证了水泥浆返至地面，盐层段有效封固。该盐穴储气库定向井固井技术在金坛储气库二期二阶段现场应用11井次，固井质量显著提升，为其他盐穴储气库固井提供了借鉴。

Technology for Cementing Directional Wells Drilled for Salt Cavern Gas Storages in Jintan

To improve the utilization of salt rock resources, the second stage of the Phase 2 gas storage construction in Jintan used directional cluster well instead of vertical well previously used to build the gas storages. Cluster well gas storage helps maximize the storage capacity and gas production rate. Problems associated with directional well drilling are hole size of irregularity and eccentricity of casing string. As to well cementing, since the salt is buried in shallow depth with low temperature, cement slurry formulated with saltwater has poor stability at low temperatures, the filtration rate of the cement slurry is difficult to control, and the compressive strength of the cement slurry develops slowly. Losses of cement slurry in the second interval result in cement slurry that is unable to return to the surface. Based on the requirements of salt cavern gas storage on well cementing job, study was conducted on low temperature high strength cement slurry, viscosified saltwater spacer and well cementing operation techniques. The study results showed that the low temperature high strength saltwater cement slurry developed had good stability, fast developed compressive strength, and high later strength, satisfying the needs of cement slurry for cementing directional well for salt cavern gas storages. Viscosified saltwater spacer in combination with techniques for improving the centralization of casing string increased the displacing efficiency of fluid in washout sections and hole sections of irregular sizes, preventing choke and block during well cementing. Use of low flowrate displacement ensured the cement slurry to return to the surface, making the salt section effectively cemented. This well cement technology has been used for 11 times in the second stage of the Phase 2 gas storage construction, the quality of well cementing operation was significantly improved. This technology has provided a reference for other salt cavern gas storage construction.