抗高温高密度可逆油基钻井液体系

Reversible oil-based drilling fluid with high-temperature resistance and high density

为满足高温深井钻井需求以及弥补油基钻井液在完井固井和环境保护方面的不足,基于非离子表面活性剂CN-2构建了CO_(2)和HAc双响应性可逆油基钻井液体系,并比较了两种纳米颗粒(OTS-KH550/SiO_(2)、CTAB/SiO_(2))对体系性能的影响。结果表明:所建体系在CO_(2)或HAc诱导下从油包水转相为水包油,该转相可由CaO或NaOH诱导回转。CN-2与OTS-KH550/SiO_(2)协同稳定的乳状液性能更佳,抗温达250℃。纳米颗粒OTS-KH550/SiO_(2)的加入不会影响钻井液体系的可逆性能,且能显著地改善体系抗高温性能,使得体系在低油水比50∶50~60∶40、高密度1.8~2.1 g/cm3及高温180~200℃条件下均具有良好的流变性能和滤失性能。含油钻屑、油基滤饼均可通过CO_(2)鼓泡或HAc溶液浸泡很容易地被清洗。通过红外光谱分析和微观观察揭示机理为:在CO_(2)或HAc诱导下,乳化剂发生盐化,亲水性增强,促使乳状液从油包水转相为水包油,从而所制油基钻井液易于被水清洗。纳米颗粒OTSKH550/SiO_(2)吸附在油水界面上并形成一层致密的颗粒膜,阻隔液滴聚并,强化了乳状液体系的抗高温稳定性。

To meet the requirements of deep well drilling at high temperature and make up for the deficiencies of oil-based drilling fluid in well completion and cementation and environmental protection,CO2 and HAc dual-responsive reversible oil-based drilling fluid was built based on the use of nonionic surfactant CN-2,and the effects of two nanoparticles(OTS-KH550/SiO_(2)and CTAB/SiO_(2))on the performance of the drilling fluid were compared.The results show that the drilling fluid can invert from water-in-oil to oil-in-water under CO_(2)or HAc induction,and the phase inversion can be reversed under CaO or NaOH induction.The emulsion co-stabilized by CN-2 and the nanoparticle OTSKH550/SiO_(2)has better performance,with a temperature resistance of up to 250℃.The addition of nanoparticle OTS-KH550/SiO2 will not affect the reversibility of the drilling fluid,and can remarkably improve the high temperature resistance of the fluid,and enable the fluid to achieve good rheological and filtration properties at the low oil-water ratio of 50∶50-60∶40,high density of 1.8-2.1 g/cm^(3)and high temperature of 180-200℃.The oily cuttings and oil-based filter cakes can be readily cleaned up by CO_(2)bubbling or soaking in HAc solution.The mechanism revealed by infrared spectrum analysis and microscopic observation is as following:the emulsifier transforms into its salt under CO_(2)or HAc induction,and its hydrophilicity is enhanced,thus inducing the phase inversion of the emulsion from water-in-oil to oil-in-water.As a result,the oil-based drilling fluid can be readily cleaned up by water.In addition,the nanoparticle OTS-KH550/SiO_(2)formed a compact particle film on the oil-water interface to prevent droplets from coalescing,thus enhancing the emulsion stability at high temperature.