Abstract:

Well DS1 is a 6-interval exploratory well on DS buried structure in the Southern Sichuan Basin，with bottom hole temperature as high as 197 ℃. The well had some technical problems with the oil-based drilling fluid used，such as the difficulty in controlling its rheology and stability under high-temperature and high-density conditions，the difficulty in carrying cuttings under high-temperature and low-density conditions，and high risk of wellbore instability. A high-temperature resistant and high-density oil-based drilling fluid system has been formed by developing nano high-temperature resistant suspension agent，and combining with emulsifier，shear strength-improving agent，fluid loss reducer and other treatment agents. Experiments show that nano high-temperature resistant suspension agent can form a three-dimensional network structure in oil-based drilling fluid due to its "emulsification effect" and "small-size effect"，and significantly improve the stability of oil-based drilling fluid at high temperatures. The oil-based drilling fluid system has no obvious precipitation after standing at 200 ℃ for 7 days，and its settling stability and cuttings-carrying capacity have been significantly improved at high temperatures. The system has been successfully applied in well DS1. Because of its excellent settling stability at high temperatures and satisfactory slim hole cuttings-carrying capacity，the system has broad prospect for popularization and application in high-temperature deep wells. 

Key words:

"> ultra-deep well；high-temperature resistant suspension agent；oil-based drilling fluid；settling stability；cuttings-carrying capacity

摘要：

DS1井是四川盆地蜀南地区DS潜伏构造上的六开预探井，井底温度高达197 ℃，存在油基钻井液高温高密度条件下流变性和稳定性难控制、高温低密度条件下携岩困难以及井壁失稳风险大等技术难题。通过研发纳米抗高温悬浮剂，结合乳化剂、提切剂、降滤失剂等处理剂，构建了一套抗高温高密度油基钻井液体系。实验表明，纳米抗高温悬浮剂因其“乳化效应”和“小尺寸效应”可在油基钻井液中形成三维网络结构，能显著提高油基钻井液在高温下的稳定性。该油基钻井液体系在200 ℃下静置7 d无明显沉淀，高温下沉降稳定性和携岩能力得到显著提升。该体系在DS1井成功应用，表现出优异的高温沉降稳定性和良好的小井眼携岩能力，在高温深井中推广应用前景广阔。

关键词:

超深井, 抗高温悬浮剂, 油基钻井液, 沉降稳定性, 携岩能力