Song Hanxuan,Guo Jixiang,Wyclif Kiyingi,Wang Xiwen,He Aiguo,Li Jiao,Wang Li,Chen Xiangwei
During the ultra-deep well drilling process, drilling fluid tends to remain in the casing, contaminating it and affecting the progress of completion engineering. To address this issue, a screening method was employed to select nonionic surfactants, with fatty alcohol polyoxyethylene ether (AEO-7) being chosen among various types. To overcome the temperature resistance issue of AEO-7, phthalic anhydride (PA) was introduced into AEO-7, and neutralization reaction with NaHCO 3 was carried out to synthesize a novel surfactant (SEO). High-temperature and high-pressure precipitation testing equipment and high-temperature cleaning equipment were set up to study the temperature-resistant cleaning performance of SEO. Results indicate that surfactant SEO maintains good solubility in high-temperature environments in the solution through ionic bonding. At 200 °C, the cleaning efficiency of SEO solution for different types of drilling fluid residues exceeds 95 %. Additionally, SEO adsorption on metal surfaces can inhibit Cl - corrosion. Combined with micro-mechanism characterization results, SEO can disperse solid particles, adsorb organic phases, reduce interfacial tension, and achieve efficient cleaning. Field experimental results show that the surface tension retention rate of well-flushing fluid after cleaning is 95.8 %, with a solid particle content of 5.4 g/L, meeting onsite requirements and broad application prospects.
Jian Li,Jinsheng Sun,Kaihe Lv,Yuxi Ji,Jintao Ji,Jingping Liu
With the continuous exploration and development of oil and gas resources to deep formations, the key treatment agents of water-based drilling fluids face severe challenges from high temperatures and salinity, and the development of high temperature and salt resistance filtration reducers has always been the focus of research in the field of oilfield chemistry. In this study, a nano-silica-modified co-polymer (NS-ANAD) gel was synthesized by using acrylamide, isopropylacrylamide, 2-acrylamide-2-methyl propane sulfonic acid, diallyl dimethyl ammonium chloride, and double-bond-modified inorganic silica particles (KH570-SiO2) through free radical co-polymerization. The introduction of nanotechnology enhances the polymer’s resistance to high temperature degradation, making it useful as a high-temperature-resistant fluid loss reducer. Moreover, the anions (sulfonates) and cations (quaternary ammonium) enhance the extension of the polymer and the adsorption on the surface of bentonite particles in a saline environment, which in turn improves the salt resistance of the polymer. The drilling fluids containing 2.0 wt% NS-ANAD co-polymer gels still show excellent rheological and filtration performance, even after aging in high temperature (200 °C) and high salinity (saturated salt) environments, showing great potential for application in deep and ultra-deep drilling engineering.Keywords:nano-modified polymers gels;fluid-loss additive;temperature- and salt-resistant;water-based drilling fluids;ultra-deep wells
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